UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM 10-K

(Mark One)

For the fiscal year ended December 31, 2020

OR

FOR THE TRANSITION PERIOD FROM                      TO                      

Commission File Number 001-38663

Gritstone Oncology, Inc.

(Exact name of Registrant as specified in its Charter)

(510) 871-6100

Registrant’s telephone number, including area code

Securities registered pursuant to Section 12(b) of the Act:

Securities Registered Pursuant to Section 12(g) of the Act: None

Indicate by check mark if the Registrant is a well-known seasoned issuer, as defined in Rule 405 of the Securities Act. Yes ☐ No ☒

Indicate by check mark if the Registrant is not required to file reports pursuant to Section 13 or 15(d) of the Act. Yes ☐ No ☒

Indicate by check mark whether the Registrant: (1) has filed all reports required to be filed by Section 13 or 15(d) of the Securities Exchange Act of 1934 during the preceding 12 months (or for such shorter period that the Registrant was required to file such reports), and (2) has been subject to such filing requirements for the past 90 days. Yes ☒ No ☐

Indicate by check mark whether the Registrant has submitted electronically every Interactive Data File required to be submitted pursuant to Rule 405 of Regulation S-T (§232.405 of this chapter) during the preceding 12 months (or for such shorter period that the Registrant was required to submit such files). Yes ☒ No ☐

Indicate by check mark whether the registrant is a large accelerated filer, an accelerated filer, a non-accelerated filer, smaller reporting company, or an emerging growth company. See the definitions of “large accelerated filer,” “accelerated filer,” “smaller reporting company,” and “emerging growth company” in Rule 12b-2 of the Exchange Act.

If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 13(a) of the Exchange Act.  ☒

Indicate by check mark whether the Registrant has filed a report on and attestation to its management assessment of the effectiveness of its internal control over financial reporting under Section 404(b) of the Sarbanes-Oxley Act (15 U.S.C. 7262(b)) by the registered public accounting firm that prepared or issued its audit report. ☐

Indicate by check mark whether the Registrant is a shell company (as defined in Rule 12b-2 of the Exchange Act). Yes ☐ No ☒

The aggregate market value of the common stock held by non-affiliates of the registrant as of June 30, 2020 (the last business day of the registrant’s most recently completed second fiscal quarter) was approximately $198.7 million, based on the closing price of the registrant’s common stock, as reported by the NASDAQ Global Select Market on June 30, 2020 of $6.64 per share. Shares of the registrant’s common stock held by each executive officer, director, and holder of 5% or more of the outstanding common stock have been excluded in that such persons may deemed to be affiliates. This calculation does not reflect a determination that certain persons are affiliates of the registrant for any other purpose.  

The number of shares of Registrant’s Common Stock outstanding as of March 5, 2021 was 48,951,561.

DOCUMENTS INCORPORATED BY REFERENCE

Table of Contents

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PART I

Note Regarding Forward-Looking Statements

This Annual Report on Form 10-K, including "Business" in Part I Item I and "Management's Discussion and Analysis of Financial Condition and Results of Operations" in Part II Item 7, contains "forward-looking statements" within the meaning of Section 21E of the Securities Exchange Act of 1934, as amended (the “Exchange Act”). All statements other than statements of historical fact are statements that could be deemed forward-looking statements. In some cases, you can identify forward-looking statements by terminology such as “aim,” “anticipate,” “assume,” “believe,” “contemplate,” “continue,” “could,” “due,” “estimate,” “expect,” “goal,” “intend,” “may,” “objective,” “plan,” “predict,” “potential,” “positioned,” “seek,” “should,” “target,” “will,” “would,” and other similar expressions that are predictions of or indicate future events and future trends, or the negative of these terms or other comparable terminology. These forward-looking statements include, but are not limited to, statements about:

These statements relate to future events or to our future financial performance and involve known and unknown risks, uncertainties and other factors that may cause our actual results, performance or achievements to be materially different from any future results, performance or achievements expressed or implied by these forward-looking statements. Factors that may cause actual results to differ materially from current expectations include, among other things, those listed under “Item 1A. Risk Factors” and elsewhere in this Annual Report on Form 10-K. Any forward-looking statement in this Annual Report on Form 10-K reflects our current views with respect to future events and is subject to these and other risks, uncertainties and assumptions relating to our operations, results of operations, industry and future growth. Given these uncertainties, you should not place undue reliance on these forward-looking statements. Except as required by law, we assume no obligation to update or revise these forward-looking statements for any reason, even if new information becomes available in the future.

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This Annual Report on Form 10-K also contains estimates, projections and other information concerning our industry, our business, and the markets for our product candidates, including data regarding the estimated patient population and market size for our product candidates, as well as data regarding market research, estimates and forecasts prepared by our management. Information that is based on estimates, forecasts, projections or similar methodologies is inherently subject to uncertainties, and actual events or circumstances may differ materially from events and circumstances reflected in this information. Unless otherwise expressly stated, we obtained this industry, business, market and other data from reports, research surveys, studies and similar data prepared by third parties, industry, medical and general publications, government data and similar sources. In some cases, we do not expressly refer to the sources from which this data is derived. In that regard, when we refer to one or more sources of this type of data in any paragraph, you should assume that other data of this type appearing in the same paragraph is derived from the same sources, unless otherwise expressly stated or the context otherwise requires.

Item 1. Business.

Overview and Strategy

We are a biotechnology company developing targeted immunotherapies for cancer and infectious disease. Our approach seeks to generate a prophylactic or therapeutic immune response by leveraging insights into the immune system’s ability to recognize and destroy diseased cells by targeting select antigens. We initially focused on harnessing the natural power of a patient’s own immune system to recognize short tumor-specific peptide sequences presented on cancer cells, referred to as tumor-specific neoantigens, or TSNA, in order to destroy tumor cells. More recently, we extended our programs to include viral antigens displayed on the surface of virus-infected cells. Our programs are built on two key pillars – first, our proprietary Gritstone EDGE artificial intelligence platform, which enables us to identify antigens that can be recognized by the immune system with high accuracy; and second, a potent immunotherapy platform which we have engineered to deliver the selected antigens and drive the patient’s immune system to attack and destroy tumors or virally-infected cells.

We initiated the Phase 2 portion of our Phase 1/2 first-in-human clinical trial of our personalized immunotherapy product candidate, GRANITE, and the Phase 2 portion of our Phase 1/2 clinical trial of our “off-the-shelf” immunotherapy product candidate, SLATE (also targeting TSNA), in the fourth quarter of 2020, both for the treatment of several common solid tumors and being evaluated in combination with immune checkpoint blockade. In these studies, patients have received our immunotherapy product candidates, which have shown acceptable tolerability at doses tested as of December 31, 2020, and, importantly, we have observed substantial cytotoxic T cell responses to multiple administered TSNA and early evidence of clinical benefit. We expect to present preliminary clinical data from select cohorts in the first half of 2021. Patient selection for the two programs is distinct. SLATE patients must carry both a particular tissue type human leukocyte antigen (“HLA”), which is similar to the ABO blood type, but with more variants, and at least one of twenty specific gene mutations, with a particular focus upon common KRAS gene mutations, to be eligible for this “off-the-shelf” product candidate. In contrast, GRANITE patients receive an immunotherapy product candidate made specifically for them, based upon their tumor DNA/RNA sequence. Separately, we have also identified a lead product candidate against CT83, a cancer testis antigen target in a separate product class of bispecific antibodies (“BiSAb”), which are designed to offer an alternative form of off-the-shelf therapy against our EDGE-identified novel tumor-specific antigens. We expect to file an IND for this program in 2022.

Immuno-oncology represents one of the most significant advances in the history of cancer treatment. In 2014, the first checkpoint inhibitor was approved and today, despite only a modest breadth of efficacy across patients, this class of therapies is predicted to reach over $32.0 billion in combined global sales by 2022. However, because checkpoint inhibitors work through relatively non-specific stimulation of occasional, pre-existing, tumor-specific (typically TSNA-specific) T cells, they are effective in only a subset of patients, with objective responses (substantial tumor shrinkage) observed in 0-20% of all patients with cancer of the lung, breast, prostate, colon/rectum and ovary (the major lethal solid tumor types). Many patients appear not to possess meaningful numbers of T cells that recognize their tumor (so-called “cold” tumors). We believe the path to broader immuno-oncology efficacy and more meaningful clinical responses resides in the de novo generation of new, potent, tumor-specific T cell responses.

The first pillar of our tumor-specific cancer immunotherapy approach is our understanding of tumor antigens and the application of our artificial intelligence-based, proprietary Gritstone EDGE platform to predict (and for SLATE and the bispecific program, to help validate) often novel or unique tumor antigens on tumor cells. EDGE is a proprietary machine learning model that uses DNA/RNA sequence data derived from a patient’s tumor biopsy to predict which mutations will generate TSNA most likely to be presented on the tumor cell surface. While there are frequently hundreds of mutations in the DNA of a tumor cell, only approximately 1-2% of these mutations are actually transcribed, translated and processed into a unique “non-self” peptide sequence that is presented on the surface of tumor cells and can therefore be recognized by the patient’s own T cells. Some TSNA arise in classical oncogenes, the growth-related genes which are recurrently mutated across cancer patients because the mutations promote the formation and progression of cancer-like behavior. These are referred to as driver gene mutations, and such mutations that form TSNA are the basis of the SLATE product concept. Few driver gene (or “shared”) TSNA are described in the scientific literature, and Gritstone uses

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EDGE to predict new shared TSNA, and then validate them by directly observing them on the surface of human tumor cells from cancer patients. However, shared TSNA are relatively rare (found in approximately 10-15% of patients with lung or colorectal cancer), and most TSNA are unique to each individual patient’s tumor (termed “private”), arising as mutations in random genes, that are thought to be neutral for the cell’s growth. Previously available technologies cannot predict the presence of TSNA with sufficient accuracy to design a therapy that is likely to be effective, and so Gritstone built the EDGE platform. Applying this platform to sequence data from human tumors, we have shown a 9-10-fold improvement in prediction performance with our platform compared to traditional approaches. These data were published in Nature Biotechnology in December 2018 (Bulik-Sullivan, et al, Nature (2018)), and a US patent covering the concept issued to Gritstone in 2018. Of note, a large academic study published in Nature Biotechnology confirmed the utility of this class of machine learning approaches for the prediction of HLA presented peptides and TSNA (Sarkizova, et al, Nature (2019)). In our bispecific program, EDGE is used to nominate targets arising from tumor specific genes, such as cancer testis antigens (“CTAs”), and then validate and characterize them on the surface of human tumor cells analogously to TSNA in the SLATE program. We continue to identify novel tumor antigens and improve the performance of the EDGE model.

The second pillar of our tumor-specific cancer immunotherapy approach is our potent antigen delivery system, which delivers TSNA to patients in order to direct a robust T cell response to those TSNA predicted to be presented on the patient’s tumor. Grounded in traditional infectious disease vaccinology, this two-step immunization utilizes prime and separate boosts to educate and expand the patient’s T cells to detect TSNA and destroy tumor cells. In non-human primate models, we have demonstrated a profound and specific CD8+ and CD4+ T cell response to antigens administered in this way. Similarly, our tumor-specific immunotherapy candidates, SLATE and GRANITE, comprise a sequential immunization of a viral-vector based prime and boosts with self-amplifying mRNA (“SAM”) delivered by intramuscular injection, which we refer to as heterologous prime-boost. In our SLATE product candidate series, the viral-vector prime and RNA boosts both contain the same fixed TSNA cassette that is designed for the subset of patients who carry these antigens, whereas for our GRANITE product candidate, each of the viral-vector prime and RNA boost immunizations contain a patient-specific set of predicted TSNA. Importantly, we also have the capability to manufacture these products at our own fully-integrated GMP biomanufacturing facilities. The ability to control the manufacturing of high-quality tumor-specific immunotherapy products, and scale production, if early data are positive, is critical for efficient clinical development and commercialization. We have invested significant resources in our Cambridge, Massachusetts sequencing lab and our Pleasanton, California biomanufacturing facility to address these needs and position ourselves to control the critical steps in the production of our tumor-specific immunotherapy candidates.

The SLATE and GRANITE Phase 1/2 clinical trials involve the combined use of our heterologous prime-boost system together with checkpoint inhibitor therapy. To support this, we entered into a clinical trial collaboration and supply agreement with Bristol-Myers Squibb Company to evaluate the safety and tolerability of SLATE and GRANITE in combination with OPDIVO (nivolumab) and in combination with OPDIVO plus YERVOY (ipilimumab), in patients with advanced solid tumors.

Our off-the-shelf, TSNA-directed immunotherapy product candidate, SLATE, utilizes the same heterologous prime-boost approach, but SLATE contains a fixed cassette with TSNA that are shared across a subset of cancer patients rather than a cassette unique to an individual patient, which distinguishes it as a potential off-the-shelf alternative to our personalized manufactured product candidate, GRANITE. SLATE is therefore designed to be readily available for rapid initiation of therapy and is less expensive to manufacture than a personalized product. Patient selection is achieved by screening the patient’s tumor for driver mutations using commercially-available genomic screens and identifying the patient’s HLA type from blood with a standard clinical assay.

We initiated a first-in-human Phase 1/2 clinical trial of our SLATE in the third quarter of 2019, evaluating SLATE in combination with immune checkpoint blockade for the treatment of patients with metastatic non-small cell lung cancer (“NSCLC”), pancreatic ductal adenocarcinoma and microsatellite stable colorectal cancer (“MSS-CRC”), as well as in patients with other solid tumor types who have relevant mutation/ HLA combinations. We presented preliminary efficacy, immunogenicity, and safety data from the Phase 1 portion of the study in July 2020, which demonstrated the induction of CD8+ T cells against multiple KRAS driver mutations, with the most pronounced response against immunodominant neoantigens such as TP53mut, and showed favorable safety results.

In the fourth quarter of 2020, we initiated single-arm Phase 2 expansion cohorts with SLATE in NSCLC patients with relevant KRAS mutations who have progressed on prior immunotherapy, and patients with tumors where a relevant TP53 mutation exists.

Our personalized immunotherapy product candidate, GRANITE, has two potential benefits in comparison with SLATE – (1) the potential for a larger addressable patient population, since many patients with common solid tumors such as NSCLC will have sufficient private TSNA to merit use of our immunotherapy; and (2) a greater chance that patients will mount an immune response to multiple TSNA in parallel, which may reduce the chances of a tumor developing acquired resistance by altering a particular neoantigen or its cell-surface presentation. The GRANITE process begins with receipt of a routine tumor biopsy from the patient. We utilize our in-house sequencing capabilities on the tumor sample and then apply our proprietary EDGE platform to derive a set of predicted TSNA likely to be presented on the patient’s tumor. Using these TSNA, we design a highly potent personalized

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immunotherapy candidate containing the relevant neoantigens to be administered by simple intramuscular injection. We have designed each of our tumor-specific immunotherapy candidates such that oncologists will not have to alter their treatment practices, and we believe this approach would extend the utility of our product candidates into the community oncology setting and not limit their use to scarce centers of excellence. We believe that as a result of its design, our tumor-specific immunotherapy candidate has the potential to expand the efficacy of immunotherapy into broader patient populations.

We initiated a first-in-human Phase 1/2 clinical trial of our first personalized immunotherapy product candidate, GRANITE, in the fourth quarter of 2018, evaluating it in the treatment of advanced solid tumors, including MSS-CRC, gastro-esophageal cancer (“GEA”), NSCLC, and bladder cancer, in each case in combination with checkpoint inhibitors. We presented preliminary efficacy, immunogenicity, and safety data up to dose level 3 from the Phase 1 portion of the study in July 2020, which demonstrated consistent, strong neoantigen-specific CD8+ T cells generated in all patients tested and evidence of clinical benefit, as well as favorable safety results.

In the fourth quarter of 2020, we advanced into Phase 2 expansion cohorts. The Phase 2 portion of the GRANITE Phase 1/2 study includes a cohort for patients with MSS-CRC who have progressed on FOLFOX/FOLFIRI therapy and a second cohort for patients with GEA who have progressed on chemotherapy.

We are also leveraging our expertise in cancer genomics and our tumor antigen discovery platform to go beyond shared TSNA and identify novel peptide sequences (not mutated) that may be shared across common tumor types (tumor-specific shared antigens), which we believe are likely to have value as targets to direct T cells onto tumors specifically. Shared antigen targets enable us to develop additional therapeutic approaches to redirect T cells to tumors using these highly specific targets, such as our BiSAb platform. Redirecting T cells to tumors using BiSAb has been validated in the treatment of B cell malignancies with compelling data generated using CD19-CD3, CD20-CD3 and BCMA-CD3 bispecific antibodies. The CD3 binding domain recruits and activates T cells, and the CD19, CD20 or BCMA binding domains ensure recognition and killing of the B cells by the activated T cells. While these approaches do not distinguish between normal and malignant B cells, which leads to the killing of normal B cells, human survival in the absence of normal B cells is feasible (intravenous immunoglobulin infusions can be administered as needed). We believe the strategy is viable given the existence of absolute B cell lineage specific markers (such as CD19, CD20, CD22, and BCMA), which are not found on any other normal tissues. Applying this concept to the treatment of solid tumors has proven to be challenging because most solid tumor cell-surface markers are also expressed on vital normal tissues, which will result in on-target, off-tumor toxicities. Gritstone’s proposed solution to this problem is to develop BiSAb that bind to HLA-peptide complexes on the surface of tumor cells where the peptide is either a mutant peptide (derived from a shared neoantigen such as KRAS) or a peptide from a cancer testis antigen (a family of intracellular proteins, some of which are only expressed on normal testis tissue and tumors). Identifying antibody fragments that only bind to the specific HLA-peptide complex is challenging but achievable (so-called TCR-mimetic antibodies), and these can be combined with traditional CD3 binding domains to generate BiSAb that we have shown have the potential to kill tumor cells potently and specifically in vitro and in vivo. Gritstone has a development candidate against CT83, a novel bispecific antibody target with compelling activity. CT83 is an unexplored solid tumor HLA-p target with high tumor density, high patient prevalence, and low expression in off-target tissues. It is a high affinity binder selected for maximal efficacy and minimal off-target toxicity, screened against off-target peptides identified using Gritstone EDGE and mass spec. CT83 is prevalent in common solid cancers with significant unmet need, such as esophageal, gastric adenocarcinoma, lung adenocarcinoma, and lung squamous cell carcinoma. We expect to file an IND for this program in 2022.

An additional therapeutic approach that uses shared tumor-specific antigens is the modification of the receptors of the patient’s own T cells to redirect them to recognize tumor targets (adoptive T cell therapy). In August 2018, we announced our first collaboration supporting this strategy with bluebird bio, Inc., or bluebird, whereby we will identify up to 10 tumor-specific targets and associated T cell receptors for some of the selected targets for therapeutic application within bluebird’s cell therapy platform.

In our infectious disease portfolio, we are advancing development of a second-generation vaccine candidate, CORAL, against SARS-CoV-2, the virus that causes COVID-19, which is designed for both prolonged protection and potency against emerging Spike variants. We have received a grant from the Bill & Melinda Gates Foundation (the “Gates Foundation”) to support the preclinical evaluation of the vaccine candidate. The National Institute of Allergy and Infectious Diseases (“NIAID”) is supporting development of the Phase 1 clinical trial through the Infectious Diseases Clinical Research Consortium (“IDCRC”).

First generation COVID-19 vaccines generate a strong antibody response against SARS-CoV-2. These vaccines elicit neutralizing antibodies that can recognize the surface Spike protein of the virus and attack it prior to cell infection. However, antibody responses may wane over time and long-term durability of protection remains unknown. Additionally, mutations in SARS-CoV-2 continuously arise, including in the Spike protein, and may further reduce clinical protection derived from vaccine-induced neutralizing antibodies to Spike. Analysis of blood from convalescent COVID-19 patients shows that recovered patients have both T cell and antibody immune responses. This is expected because T cells play a fundamental role in protective immunity against viruses. If a virus successfully evades neutralizing antibodies and infects a cell, the cell displays pieces of the virus on its surface, which T

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cells can recognize. Since T cells remember what viruses look like, they may provide longer, more robust immunity, complementing antibody-based immunity. Mutations in the Spike protein may reduce protection by antibodies (since the antibody target has changed its shape) and broad T cell immunity and long-term memory to different viral proteins may provide a second layer of clinical protection.

We believe Gritstone’s CORAL vaccine candidate has the potential to improve both T cell and antibody responses to Spike and other viral proteins. Additionally, by targeting several viral antigens, some of which are highly conserved between viral strains (such as SARS and SARS-CoV-2), we believe our vaccine candidate may have pan-SARS/coronavirus potential to protect against future coronavirus pandemics.

Through a license agreement with the La Jolla Institute for Immunology (“LJI”), one of the leading global organizations dedicated to studying the immune system, we have access to validated SARS-CoV-2 antigens that have been identified through LJI’s studies of hundreds of patients recovering from COVID-19. Using these antigens and our proprietary Gritstone EDGE and vaccine platform technologies, we have developed a novel vaccine candidate containing Spike (similar to first generation vaccines) but also additional viral antigens that offer potential targets for broad T cell immunity.

We have conducted preclinical studies demonstrating that our SARS-CoV-2 vaccine candidate induced significant and sustained levels of neutralizing antibodies and T cells against the Spike protein, plus a broad T cell response against epitopes from multiple viral genes outside of Spike. The Gates Foundation supported the preclinical evaluation of the vaccine candidate.

Gritstone and the NIAID, part of the National Institutes of Health, are collaborating on a Phase 1 clinical trial to be conducted through the NIAID-supported IDCRC. The IND has been approved, and volunteer subjects enrollment will start imminently.

To deliver on the promise of our novel therapeutic approach, we have assembled a highly-experienced management team with focused expertise in each of our core disciplines of cancer genomics, immunology and vaccinology, clinical development, regulatory, and biomanufacturing from several leading biotechnology companies, including Clovis Oncology, Inc., Pfizer Inc., Genentech, Inc. and Foundation Medicine, Inc. Our co-founder, Dr. Andrew Allen, brings experience as a co-founder and Chief Medical Officer of Clovis Oncology, Inc., with prior experience in various leadership roles at Pharmion Corporation and Chiron Corporation, where he worked on Proleukin (IL-2), the first cancer immunotherapy. Our scientific advisory board includes selected experts in relevant disciplines, including Dr. Timothy Chan (Memorial Sloan Kettering Cancer Center) and Dr. Naiyer Rizvi (Columbia University Medical Center) who together first demonstrated that TSNA are key T cell targets in cancer patients responding to checkpoint inhibitor therapy, as well as Dr. James Gulley (National Cancer Institute) who is an international expert in cancer immunotherapy with a focus on vaccines.

We have assembled a team of industry leaders, each possessing specific expertise that we believe will allow us to build and deploy our proprietary vaccine platform and EDGE technology to deliver groundbreaking immunotherapies for cancers and infectious diseases. Our strategy to achieve this includes the following key components:

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Finally, starting in 2021, we intend to expand the application of our immunotherapies beyond oncology and begin research and development of vaccines for certain other diseases:

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Our Immuno-Oncology Based Approach to Cancer Therapy

Immuno-Oncology and Tumor-Specific Neoantigens

Immuno-oncology is an emerging field of cancer therapy that aims to activate the immune system to enhance and/or create anti-cancer immune responses, as well as to overcome the immuno-suppressive mechanisms that cancer cells have developed against the immune system. It is now well established that the immune system can, on occasion, successfully eliminate all tumor cells, leading to long-term benefit, even cures, in some patients with solid tumors. The primary challenge in immuno-oncology is to extend this useful biology to many more cancer patients, and to do so earlier in the treatment paradigm. Understanding which cells of the immune system are critical, what they recognize on tumor cells, and why they are typically absent or ineffective in cancer patients is core to overcoming this challenge. T cells are the vital foot soldiers in the immune attack upon cancer cells. T cells have evolved to recognize “foreign” markers on cells infected by viruses; and DNA mutations, which are a hallmark of cancer, often lead to the generation of such “foreign” markers, which are different from normal or “wild-type” proteins. Exploitation of this cancer cell vulnerability using new biological and computational tools lies at the heart of our programs.

Critical Importance of T Cells

The most critical components of the immune response to tumors are T cells, white blood cells which mature in the thymus gland. T cells can be classified into two major subsets, CD4+ T cells and CD8+ T cells, based on expression of CD4 or CD8 markers on the surface of the T cell. CD4+ T cells (also referred to as helper T cells) provide help to the immune response by secreting cytokines that enhance the activation, expansion, migration and effector functions of other types of immune cells. CD8+ T cells (also referred to as cytotoxic or “killer” T cells) can directly attack and kill cells they recognize as abnormal. An activated CD8+ T cell attacks and kills a target cell when the T cell encounters its target and the T cell receptor, or TCR, recognizes and binds to a specific protein complex on the target cell. This protein complex is comprised of a short peptide (fragment of a protein) bound to a platform molecule called, in humans, the human leukocyte antigen, or HLA, complex. This HLA/peptide complex is the antigen recognized by a T cell receptor. The peptides recognized by typical CD8+ T cells are quite short (8-12 amino acids long) and are presented on so-called Class I HLA molecules (such as HLA-A, -B or -C). The peptides recognized by typical CD4+ T cells are longer (15-25 amino acids) and are presented on Class II HLA molecules (such as HLA-DP, -DQ and -DR).

One of the primary functions of T cells is to detect and eliminate normal cells that have been infected by a virus to prevent virus spread and limit harm to the host. To accomplish this, T cells are “trained” in the thymus early in life to differentiate between HLA/peptide complexes that are “self” derived (an HLA presenting a peptide derived from a normal self-protein) and those that are “foreign” or “non-self” (an HLA presenting a peptide derived from a non-self-protein such as a viral protein). When the immune system develops early in life, T cells that recognize self peptides are eliminated in the thymus to avoid the risk of an auto-immune reaction, in a process called central tolerance. T cells that recognize a non-self peptide are nurtured and sent from the thymus to patrol the body, looking for evidence of non-self markers on cells, such as virally-infected cells. Because cancer cells carry DNA mutations, which may alter protein/peptide sequences, tumor cells can also present non-self peptides bound to HLA platforms on the cell surface and, as a result, can be recognized as non-self and destroyed by T cells. In this case, the DNA mutation in a tumor creates a novel non-self peptide sequence, which, if it can be recognized by a TCR, is called a tumor-specific neoantigen, or TSNA.

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Tumor-Specific Neoantigens

The notion that T cells can recognize TSNA on the surface of tumor cells is well established. It is only recently, however, that tools and techniques have been developed to test this idea in humans. Two advances proved critical. First, the advent of checkpoint inhibitors provided cohorts of cancer patients who developed immune responses that destroyed their tumors, leading to clinical responses that could be studied at a molecular level. Second, the development of fast, inexpensive DNA and RNA sequencing techniques provided the ability to sequence and catalog tumor DNA mutations that might give rise to neoantigens. T cells from cancer patients who had responded well to checkpoint inhibitors could then be screened against candidate neoantigens to see if the patient data supported the hypothesis that T cell recognition of TSNA could kill tumor cells effectively.

In 2014 and 2015, two of our co-founders, Dr. Timothy Chan and Dr. Naiyer Rizvi, brought these two concepts together in papers demonstrating that melanoma and lung cancer patients who responded to checkpoint inhibitor therapies had developed T cells that recognized TSNA (Snyder et al., The New England Journal of Medicine (2014); Rizvi et al., Science (2015)). Further evidence from Dr. Steven Rosenberg (Center for Cancer Research) and Dr. Ton Schumacher (Netherlands Cancer Institute) demonstrated that, in patients with solid tumors, T cells could be found infiltrating tumors that were specific for TSNA, and could be expanded and used therapeutically to kill tumor cells (Stevanovic et al., Science (2017); Schumacher and Schreiber, Science (2015)). Together, this body of research suggests that, in patients with common solid tumors, T cells can selectively destroy tumor cells through recognition of TSNA.

Immune Evasion

While some patients do respond to checkpoint inhibitor therapy with the mobilization of T cells that recognize TSNA and kill tumor cells, such patients are in the minority (0-20% for most common solid tumors (Kiy et al., Febs Letters (2013)). Research into this clinical observation has shown that patients who respond to checkpoint inhibitors typically have, prior to therapy, inflamed tumors that contain infiltrating T cells (particularly cytotoxic CD8+ T cells) and that express markers of immune activation.

Figure 1. Response in Melanoma Patients Treated with Anti-PD-1 Antibody (Pembrolizumab) is Associated with Anti-Tumor T Cell Infiltration of the Tumor at Baseline*

While the immune systems of these patients have recognized their tumors through the recognition of TSNA, the tumor-specific T cells have been shut down or inactivated in the tumor. Checkpoint inhibitors are capable of “re-activating” these T cells, but most patients fail to respond to checkpoint inhibitor treatment because tumor-specific T cells are absent from the tumor due to tumor “evasion” of the patient’s immune response. We believe it is highly likely these patients have so-called “naïve” T cells in their bodies that have the ability to recognize the TSNA on tumor cells but that have not yet been activated. As a result, immune recognition, or the activation of the naïve T cells to the tumor antigen, and the generation of a large memory tumor-specific T cell response has not yet taken place.

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Our Therapeutic Hypothesis

TSNA offer extremely attractive therapeutic targets for T cell-directed therapy because they are non-self and tumor-specific and have been shown to function as the key T cell targets in humans responding to immune checkpoint inhibitor therapies. The fact that TSNA are non-self has several key implications:

Our fundamental therapeutic hypothesis is that patients with common solid tumors often have TSNA, but the tumors have successfully evaded the patient’s immune system. Our goal is simple—to activate a potent TSNA-targeted T cell response using routine therapeutic interventions.

Our Gritstone EDGE Platform

Design of Our EDGE Platform

Neoantigens in tumors are created via a multi-step process starting with mutation in the cancer DNA and leading to mutated peptides presented by the HLA on the surface of tumor cells. To select neoantigens for immunotherapy for cancer patients, we created our EDGE platform, which captures the essential elements of neoantigen biology via a combination of laboratory assays and computational analyses. The two steps of our EDGE platform prediction process are shown in Figure 2 below.

Figure 2. EDGE Platform

EDGE Step 1—Mutation Identification

Identification of neoantigens requires accurate identification of tumor mutations and measurement of their expression levels in patient cancer specimens. To achieve this, we have built an in-house next-generation sequencing laboratory to perform deep sequencing of tumor DNA and RNA, as well as sequencing of the patient’s normal DNA. This first step in the EDGE process analyzes routine, core needle, formalin-fixed paraffin embedded tumor biopsies and identifies tens to hundreds of tumor mutated sequences.

EDGE Step 2—Neoantigen Prediction

Only a small fraction of tumor mutated sequences is expected to result in actual neoantigens presented on the surface of tumor cells. This fraction may be as low as approximately 1-2% of all mutations. To accurately predict which neoantigens will be presented

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on the surface of tumor cells, we have generated a large dataset of HLA/peptides from human tumor and matched normal tissue specimens. Our process isolates and sequences HLA/peptides, using the immunopeptidomics mass spectrometry approach. We also analyze tumors for level of RNA expression of all genes. Our dataset now comprises more than 600 tumor, normal tissue, and cell-line specimens subjected to broad (DDA) immunopeptidomics for Class I or Class II HLA. These samples span a variety of solid cancers from patients of several ancestries to ensure broad coverage of diverse patient HLA types. Each tumor specimen can yield thousands of HLA/peptides, and the total dataset has now grown to >3 million (>1.5 million unique) HLA-presented peptides.

We use a subset of these and selected published peptide datasets to train a machine-learning model for Class I neoantigen prediction in our EDGE platform. The model learns the critical DNA/RNA sequence features and other factors like RNA expression that lead to a greater likelihood of peptide presentation by the HLA. Our EDGE model analyzes mutated peptides in turn and calculates the probability that the peptide will be presented by the patient’s HLA on the surface of the tumor cell, or HLA-presented peptides. We prioritize mutations with the highest probability of presentation for inclusion in that patient’s personalized immunotherapy. A schema of EDGE model training and clinical application are illustrated in Figure 3 below. Given that HLA Class I presentation is most common in solid tumors, we initially focused on collecting data and training EDGE to predict HLA Class I peptides. Recently, EDGE was extended to also predict HLA Class II peptides and thus allow identification of neoantigens presented by the patient’s professional antigen presenting cells (“APCs”), and we now use Class II EDGE in our novel shared tumor antigen discovery programs.

Figure 3. EDGE Model Training and Application

EDGE Neoantigen Prediction Performance

Accurate TSNA prediction is critical for our personalized immunotherapy, and we have evaluated the prediction performance of our EDGE model in two ways. First, we assessed the ability of the EDGE model to predict HLA presented peptides. We then tested whether the ability to predict HLA presented peptides translated into the ability to predict which mutations give rise to neoantigens with tumor-relevant T cell responses in patients. These results were initially published in Nature Biotechnology (Bulik-Sullivan et al., Nature Biotech., (2018)) and updated in follow-on internal analyses throughout 2020.

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Prediction of HLA-Presented Peptides

To assess EDGE model performance for prediction of HLA presented peptides, we used peptides from tumor samples with HLA/peptides measured by mass-spectrometry that were not included in model training. For these test peptides, we predicted which peptides are likely to be presented on the tumor cell surface. We evaluated the quality of our predictions by calculating the positive predictive value, or PPV, which is the fraction of predicted peptides that were detected on the tumor HLA. As a benchmark, we compared performance of our prediction to that of standard binding affinity-based approaches. Averaged over the test samples, our EDGE platform achieved significant improvement over standard methods, as shown in Figure 4 below. We believe that TSNA selected by our EDGE platform have a much higher likelihood of being useful targets for immunization than those selected using previous methods.

Figure 4. Performance of EDGE Model for HLA/Peptide Prediction

Prediction of TSNA with T Cell Responses in Patients

To show that our prediction of HLA/peptide presentation enables prediction of tumor-specific neoantigens that can be targeted by T cells in patients, we assembled a large test set of independently validated, published neoantigens. The dataset comprised the largest available study from the literature, covering 39 patients with gastro-intestinal cancers who had CD8 responses against one or more neoantigens in their tumor and genomic data available for EDGE analysis. In these patients, ~4,500 mutations were comprehensively analyzed for anti-tumor immune response using tumor-infiltrating lymphocytes (“TIL”). 58 mutations were demonstrated to result in neoantigens. Applying our EDGE model to select the top mutations for each patient from DNA/RNA sequence alone to simulate GRANITE production, we found that EDGE was able to prioritize the majority of these validated neoantigens and outperformed current publicly available methods.

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These results are illustrated in Figure 5 below.

Figure 5. EDGE Platform Identification of TSNA for Immunization

Ongoing EDGE Platform Validation

To further validate our EDGE platform’s ability to identify TSNA in patients, we also analyzed peripheral blood obtained from NSCLC and prostate cancer patients receiving PD-(L)1 checkpoint inhibitors, wherein T cell recognition of predicted TSNA is assessed. This process is shown in Figure 6 below.

Figure 6. Gritstone Analysis of Neoantigen T Cell Responses in NSCLC Patients

Data from this study have shown that our EDGE platform identified TSNA-specific T cells in a majority (9/13, or 69%) of patients tested, with an average of two peptides recognized per patient in patients with detectable TSNA-specific T cells.

Genomic and immune response data from our clinical trials are serving to further validate and refine our EDGE platform.

Our Personalized Tumor-Specific Neoantigen Therapy

Overview

Our therapeutic hypothesis is that treatment with personalized TSNA-containing vectors combined with immune checkpoint inhibitor therapy will generate de novo, or augment existing, selective, TSNA-specific T cell response, unleashing the natural power of the immune system on tumor cells, potentially improving efficacy without a substantial increase in off-tumor toxicity. Our personalized immunotherapy candidates are designed to fit easily into a community oncology setting and to be administered in earlier lines of treatment rather than only in refractory or relapsed cancers. We have designed our personalized immunotherapy candidates such that oncologists will not have to alter their treatment practices, and we believe that this will extend the utility of our product candidates, if approved, into the community setting and not limit their use to scarce centers of excellence. We believe that, as a result

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of its design, our personalized immunotherapy candidate has the potential to expand the efficacy of immunotherapy into broader patient populations.

Gritstone is developing two forms of personalized immunotherapy, both of which are in clinical testing. The first, represented by the SLATE product candidate, involves the administration of a neoantigen therapy containing shared neoantigens derived from common driver mutations such as in KRAS and TP53. To be a candidate for SLATE, a patient must first be assessed by asking two questions: (1) does their tumor genome contain a DNA mutation represented within the SLATE cassette; and (2) do their cells express a specific HLA molecule that can present a particular mutated peptide as a neoantigen on the tumor cell surface? The tumor genome is routinely studied in contemporary oncology clinical practice, either using a tumor DNA gene panel test (as offered by Foundation Medicine, Tempus, Personalis, etc.) or using a peripheral blood gene panel that probes blood for the presence of mutant tumor-derived DNA (as offered by Guardant, etc.). HLA typing is routinely performed by most academic centers on a 3-5 ml peripheral blood sample. Consequently, screening patients takes approximately one week, and SLATE is designed to start very soon after a mutation/HLA match has been identified.

The second personalized immunotherapy from Gritstone is the GRANITE product candidate. This requires a routine tumor biopsy sample to be sent to Gritstone for sequencing, followed by personalized product manufacturing, with a neoantigen cassette designed uniquely for that patient. This process is described in more detail below.  

Our Immuno-Oncology Portfolio

We are developing a portfolio of cancer immunotherapy product candidates aimed at the highly targeted activation of tumor-specific T cells in solid tumors. Our leading two clinical-stage programs aim to induce a substantial neoantigen-specific CD8+ T cell response using neoantigen-containing immunotherapies. Earlier in development is our bispecific antibody program, which aims to redirect and activate the patients’ own T cells adjacent to tumors using tumor-specific HLA-peptide complexes as targets. Multiple HLA-peptide targets are under consideration for this program. T cell receptors, or TCRs, against such HLA-peptide complex targets also have potential therapeutic value if deployed in a cell therapy platform. We have elected not to develop an in-house cell therapy platform at this point, and, instead, we are using this approach in partnership with bluebird and their adoptive cell therapy platform. The internal programs are described in more detail below.

“Off-The-Shelf” Neoantigen-Directed Immunotherapy Product (SLATE) Product Concept

Using our EDGE platform, we are identifying novel neoantigens arising from genes which are recurrently mutated in cancer because their function is altered in a cancer-promoting manner. Such mutations are termed driver mutations, and they are well characterized given their importance as functional drug targets. Examples include activating mutations in KRAS or EGFR genes which drive cell proliferation and/or growth, and inactivating mutations in genes such as TP53 and APC which normally limit DNA damage or cell proliferation, respectively. As noted above, the existence of a neoantigen is determined by the combination of a mutated peptide and the presenting HLA molecule. It has been demonstrated that a common KRAS mutation (G12D), often found in colorectal cancer, could be processed by tumor cells and presented as a functional neoantigen by tumor cells carrying the HLA-C*08:02 protein. This combination of KRAS mutation and HLA is estimated to be found in 1-2% of colorectal cancer patients. KRAS mutations are also common in lung and pancreatic cancers.

Building on this observation, we have applied our EDGE antigen prediction model to common tumor driver mutations and common Class I HLA alleles and predicted a large set of candidate-shared neoantigens. We have validated several of these predicted candidate neoantigens using mass spectrometry analysis of patient-derived human tumor samples wherein we directly detect a predicted HLA-peptide complex. We have also developed a cell-line system to more efficiently assess predicted shared neoantigens and determine their validity. These data were presented publicly at the SITC conference in November 2019 and Table 1 shows the shared neoantigens, many novel, validated in clinical samples and used in the design of SLATE.

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Table 1

Population genetic analyses suggest that SLATE has the potential to result in an off-the-shelf product having an addressable population of up to 15% of patients within common solid tumor types, such as colorectal cancer or lung cancer. The process for determining which patients are eligible for SLATE therapy is illustrated below in Figure 7.

Figure 7. Gritstone’s Prime/Boost Platform Enables Multiple Product Options Including Gritstone’s Off-The-Shelf Immunotherapy Platform, SLATE

Both of our personalized immunotherapy product candidates, SLATE and GRANITE, use a neoantigen (TSNA) cassette within the same heterologous prime-boost system comprising a viral-vector based prime and SAM boosts. The vector system and its associated pre-clinical data are described below. SLATE entered Phase 1 clinical testing in August 2019 and early clinical data are presented below.

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Our “N of 1” Neoantigen-Directed Immunotherapy Product (GRANITE) Product Concept

Our GRANITE personalized immunotherapy process leverages our proprietary EDGE platform to predict the TSNA that will be presented on a patient’s tumor, allowing us to create a patient-specific (termed “N of 1”) heterologous prime-boost immunotherapy candidate that is designed to elicit a potent anti-tumor T cell response. This process is outlined in Figure 8 below.

Figure 8. Gritstone’s GRANITE Personalized Immunotherapy Process

Step 1—Routine Biopsy

Most cancer care takes place in a community oncologist’s office rather than an academic center, and we believe products should ideally be designed to be usable in these settings. We are designing and developing our product candidate for administration early in the cancer treatment paradigm, particularly where disease burden is low and a cure is perceived to be more likely. Such early care is also heavily weighted to the community oncologist setting. Consequently, our product development process necessarily begins with a routine biopsy to obtain a specimen of the tumor with a standard needle biopsy performed by an oncologist or radiologist.

Step 2—Sequencing

We then apply customized deep-sequencing and bioinformatic processes in-house to the patient’s tumor biopsy specimen and blood to derive high-quality DNA and RNA sequence information and identify tens to hundreds of tumor mutations.

Step 3—Neoantigen Prediction

This tumor mutation sequence data is then entered into our proprietary EDGE platform. Our evolving artificial intelligence platform then predicts the TSNA most likely to be presented on the tumor cell surface.

Step 4—Personalized Immunotherapy

We assemble the predicted TSNA into a patient-specific “cassette.” The cassette is incorporated into our heterologous prime-boost personalized immunotherapy candidate, which is manufactured and filled into a vial.

Step 5—Simple Injection

The vial is then shipped to the oncologist’s office where it is delivered to the patient by simple intramuscular injection. Our personalized immunotherapy candidate is designed to be administered in combination with standard checkpoint inhibitors to drive large numbers of TSNA-specific T cells to the tumor site, where they remain active.

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Antigen Delivery System for SLATE and GRANITE – Heterologous Prime-Boost

Our therapeutic goal with both SLATE and GRANITE is to drive a large and sustained T cell response against all TSNA presented on a patient’s tumor. Cancer patients may have pre-existing memory T cells directed against some of the TSNA delivered within the neoantigen cassette in their personalized immunotherapy. Boosting such pre-activated TSNA-specific T cells requires less antigen-specific stimulation than priming naïve T cells that have not yet been activated against their respective neoantigen. Importantly, early clinical data in the field suggest that, for the majority of TSNA within the immunotherapy cassette, priming naïve T cells will be required to mount a large and broad immune response. Priming naïve T cells is a multi-step process that requires a potent antigen delivery platform able to deliver cassette neoantigens in a highly immunogenic manner.

Human infectious disease vaccine experience has taught us that delivering antigens within an adenoviral vector can prime a substantial T cell response consisting of cytotoxic CD8+ T cells and CD4+ T-helper cells. We believe an adenoviral vector is one of the most potent antigen-delivery platforms to prime naïve T cells. Peptide vaccination has not been able to accomplish this goal.

We believe that continued strong immune pressure upon the tumor is likely necessary to prevent immune escape by the tumor and drive a durable clinical response. To sustain high numbers of tumor-specific T cells, the same tumor-specific antigen can be given in a different vector from that used to prime, as a boost immunization. This heterologous prime-boost concept has been shown to activate and sustain high antigen-specific T cell responses, as shown in Figure 9 below.

Figure 9. Comparison of Heterologous Prime-Boost with Homologous Prime-Boost and Prime Alone

Our Construct

Our personalized immunotherapy candidates consist of (1) a prime vector and (2) a boost vector, both of which contain (3) a neoantigen cassette:

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The prime and boost immunotherapy construction is depicted in Figure 10 below.

Figure 10. Prime and Boost Immunotherapy Construction

Our current manufacturing process includes Gritstone and qualified third-party contract manufacturing organization, or CMO, sites that are designed to operate under cGMP requirements. In 2020, we continued to build the internal capability to manufacture our products entirely using internal facilities and staff for reasons of process improvement, intellectual property development, economic advantage, logistical flexibility, control of drug quality and security of drug supply. In brief, this manufacturing process includes tumor sequencing and TSNA prediction (for GRANITE), TSNA cassette design and synthesis, production of TSNA cassette plasmid and subsequently ChAdV and SAM manufacture containing the TSNA cassette, lipid nanoparticle encapsulation of the SAM, and some elements of release testing. Although we have developed these capabilities, we will assess on an ongoing basis which aspects will continue to be outsourced, and these may change over time. SLATE manufacturing, as a fixed, “off-the-shelf” product, is not time-sensitive and is relatively straightforward operationally. GRANITE, on the other hand, is an “N of 1” product and is manufactured in real time for each patient, which involves a greater logistical burden. The GRANITE manufacturing process starts when tumor samples are received by our sequencing lab in Cambridge, Massachusetts. Our EDGE platform is used to select 20 appropriate genetic sequences for neoantigen manufacturing, and these genetic sequence cassettes are inserted into plasmid backbones. The ChAdV vector, which encodes the genetic sequence in the cassette, is sent to our Pleasanton, California facility for manufacturing the prime immunotherapy, and the SAM vector, which encodes the genetic sequence in the cassette, is used for manufacturing the boost immunotherapy. This end-to-end process, from biopsy receipt to shipment of the personalized heterologous prime-boost immunotherapy to the clinical site for patient administration, initially takes approximately 16-20 weeks. This period is broadly consistent with the stated production and release times for other personalized immunotherapy approaches (mRNA or peptide) described in the literature and, importantly, acceptable for deployment in early treatment of cancer patients in the adjuvant setting, where clinical urgency is lower as compared to the relapsed or refractory late stage setting, in which adoptive T cell therapy may be utilized.

Our Preclinical Non-Human Primate Data

Our goal is to drive a large and sustained TSNA-specific T cell response to control tumor growth and/or eradicate the tumor. Published data from adoptive T cell therapies provide preliminary guidance on clinically efficacious T cell levels in patients. These

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studies suggest that T cell levels of approximately 10,000 antigen-specific T cells per milliliter of blood measured in patients four weeks post-infusion indicate clinical benefit.

We have focused our preclinical program on assessing the potency of our immunotherapy candidate in non-human primates, or NHPs, because published data suggests that NHPs’ immune responses to our immunotherapy candidate will better predict human data than murine models, due to the comparative similarities between NHP and human immune systems. Preclinical and clinical studies have shown that T cell responses induced in NHPs were predictive of responses in human clinical trials—the same relative potency was observed for different vaccinations in NHPs and humans. In these studies, a small 1.5- to three-fold decrease in absolute T cell response was measured when comparing NHPs to humans. By contrast, murine models, while simple, have been shown to be less likely to predict outcomes of cancer immunotherapy in humans, believed to be due to the many differences in immune system components between humans and mice.

We have completed two preclinical studies in NHPs to demonstrate the ability of our heterologous prime-boost immunotherapy approach to prime a potent immune response against the non-self model antigens delivered within the cassette. We constructed ChAdV and SAM vectors encoding viral, non-self model antigens because NHPs do not have tumors or TSNA. These antigens are derived from Simian Immunodeficiency Virus (“SIV”) which is the monkey-tropic version of HIV. We collected blood samples, which include T cells, throughout the studies pre- and post-immunization to measure the kinetics and level of T cell responses specifically directed against the model antigens. T cells were isolated from the blood, and the number of antigen-specific T cells are reported as spot forming cells, or SFCs, per 10⁶ peripheral blood mononuclear cells, or PBMCs, which is a measure of the number of antigen-specific cytokine secreting cells (typically T cells) in an NHP. CD8+ T cells comprise one of the critical fractions of T cells quantified with this T cell assay.

In our experiments, the NHPs immunized with ChAdV showed a rapid priming of T cell responses that peaked 14-21 days after immunization, with combined immune responses to all six non-self model antigens of approximately 2,000 spot-forming cells, or SFCs, per 10⁶ PBMCs. These data are consistent with immune responses reported in the literature for adenoviral vectors. Administration of a SAM boost, four weeks after the ChAdV prime, increased T cell responses approximately two-fold, with combined immune responses to all six non-self model antigens of approximately 4,000 SFCs per 10⁶ PBMCs measured seven days after the SAM boost, as shown in Figure 11 below. These T cell responses increased further after a second SAM boost at week 12, to around 5,000 SFCs per 10⁶ PBMCs and were maintained at these levels for four weeks without further boosts. T cell responses to each individual antigen were broadly comparable in magnitude for four of the six antigens administered. We anticipate that this breadth of T cell response against multiple antigens delivered within the cassette will be essential for the control of tumors within a patient.

Figure 11. Immune Response in NHPs to Heterologous Prime-Boost Immunotherapy Without Co-Administration of Checkpoint Inhibitors

The literature suggests that the addition of immune checkpoint inhibitors increases T cell expansion when combined with a vaccine. To study this concept, we administered our immunization to NHPs in combination with the checkpoint inhibitor anti-CTLA-4. Co-administration of anti-CTLA-4 monoclonal antibodies, or mAb, with the ChAdV immunotherapy significantly increased ChAdV priming with a combined T cell response of approximately 7,500 SFCs per 10⁶ PBMCs observed four weeks after immunization, as shown in Figure 12 below. The SAM boost administered four weeks after the prime immunization with anti-CTLA-

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4 increased the antigen specific T cell response further, reaching T cell levels greater than 10,000 SFCs per 10⁶ PBMCs. A second SAM boost, in combination with the anti-CTLA-4 antibody given eight weeks after the first boost immunization, expanded the antigen-specific T cells further to peak levels reaching greater than 14,000 SFCs per 10⁶ PBMCs one week after the boost, which were maintained at levels between 9,000-10,000 SFCs per 10⁶ PBMCs for several weeks. Thus, our heterologous prime-boost immunotherapy approach induced T cell numbers between 5,000-14,000 SFC per 10⁶ PBMCs that were sustained over 16 weeks.

Figure 12. Immune Response in NHPs to Heterologous Prime-Boost Immunotherapy in Combination with Checkpoint Inhibitor Anti-CTLA-4

In order to compare the number of robust antigen-specific T cells induced by our heterologous prime-boost approach in NHPs directly to the literature data from adoptive T cell therapies, we converted our units of SFCs per 10⁶ PBMCs to units of CD8+ T cells per milliliter of blood and plotted them against the T cell data from various clinical studies (which we also converted, where necessary, to T cells per milliliter of blood). One milliliter of blood is estimated to contain around three million PBMCs. The comparative data suggest that the antigen-specific CD8+ T cell numbers reached with our immunotherapy in NHPs (shown in the leftmost bar of Figure 13 below) is in the range of the T cell levels achieved in cancer patient clinical responders to adoptive T cell therapies (shown in the three rightmost bars in Figure 13 below), even when anticipating a 1.5- to three-fold decrease in the number of T cells induced in humans versus NHPs (as noted in the literature). Such substantial T cell numbers have not, to our knowledge, been reached with a therapeutic cancer vaccine in clinical studies to date. Furthermore, in addition to priming numerically substantial T cell responses against the cassette neoantigens, our immunotherapy regimen has been shown to induce T cells of high functional quality in NHPs, with a cytokine secretion profile seen in highly functional and cytotoxic T cells.

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Figure 13. Comparison of Number of T Cells Induced by Our Immunotherapy in NHPs to Number of T Cells Observed in Clinical Responders to Adoptive T Cell Therapies

We believe that continued immune pressure upon the tumor is likely necessary to prevent immune escape by the tumor and consequently drive a durable clinical response. High T cell titers persisting for at least six (6) months were induced by the heterologous prime-boost immunotherapy approach in combination with anti-CTLA-4, as shown in Figure 14 below.

Figure 14. Gritstone’s Immunotherapy Platform ChAdV + SAM + anti-CTLA-4

A subset of these same NHPs was studied two years after their first priming injection, to determine persistence of antigen-specific T cells and presence of T cell memory. A strong memory population of T cells was detected (Figure 15) and when the NHPs were re-boosted with SAM and ipilimumab, a very strong CD8+ SIV antigen-specific T cell boost response was elicited, such that an average of approximately 12% of peripheral CD8+ T cells were specific to our six administered antigens (Figure 16). The boosted antigen-specific CD8+ T cells demonstrated strong cytolytic activity as shown in a killing assay two weeks after the boost (Figure 17).

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Figure 15. Antigen-specific T cell response in NHP 2-years post vaccination demonstrates large T cell memory population

(Left) IFNg ELISpot (spots per million PBMCs) for six SIV antigens for each animal two-years post-immunization. (Right) Percentage of each T cell population out of all antigen-specific T cells (as measured by tetramer staining) at two-years post-immunization (average of six animals). Naïve (CD45RA+CCR7+), Teff (CD45RA+CCR7-), Tem (CD45RA-CCR7-), Tcm (CD45RA-CCR7+)

Figure 16. Re-immunization of NHP 2-years post-prime results in strong increase in antigen-specific T cell response

IFNg ELISpot (spots per million PBMCs) for six SIV antigens for each animal two-years post immunization (Left) and one-week post re-immunization with SAM and ipilimumab (Right). Red stars represent antigens that were too numerous to count and were set to the maximum detectable value.

Figure 17. Re-immunization of NHP, 2-years post-prime, expands antigen-specific T cells with cytolytic activity

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Effector T cells enriched from PBMCs 2 weeks post immunization were combined at the specified ratio with peptide loaded CFSE stained PBMCs, for each animal, and incubated for six hours. Target cell death was measured by 7-AAD staining. SIV-target cells loaded with six SIV antigens encoded by the immunotherapy, WLS-target cells loaded with negative control peptides, not encoded by the immunotherapy. 

Safety

We have performed a ten-week toxicity study governed by Good Laboratory Practice, or GLP, regulations of the ChAdV and the SAM prime-boost in NHPs to assess safety. The heterologous prime-boost immunotherapy, when administered intramuscularly, was well tolerated at the clinical maximal dose of each therapy.

Clinical Development and Early Data

We are employing an innovative and flexible clinical study design, which is similar for both SLATE and GRANITE in an effort to execute a potentially faster-to-market strategy in a rapidly evolving and competitive treatment landscape. In order to accelerate the execution of our Phase 1 and Phase 2 program, we are using a seamless Phase 1/2 trial design. A seamless design refers to an integrated Phase 1 and Phase 2 trial protocol that allows rapid transition following dosing and tolerability confirmation during the Phase 1 portion to establishing proof-of-concept in the Phase 2 cohort expansion portion without compromising patients’ safety or incurring delay for analysis or approval. Data obtained from the Phase 1/2 trials will inform the design and initiation of Phase 2/3 studies with registrational intent in the metastatic and adjuvant settings in specific tumor types, for both programs. Advanced pancreatic cancer, NSCLC and MSS-colorectal cancer are the initial target indications for SLATE, since KRAS mutations are common in these tumor types, and the SLATE cassette contains a large number of KRAS mutations. There is also a cohort for patients with other solid tumor types who possess the appropriate combination of tumor mutations and HLA type. Advanced NSCLC and gastro-esophageal, bladder and MSS-colorectal cancers are the initial target indications for the Phase 1 portion of our GRANITE clinical trial. These indications have been selected for several reasons, including high mutational load, response to checkpoint inhibitors, large patient populations, manufacturing time, emerging treatment landscape, regulatory pathway, the ability to combine personalized immunotherapies with immune checkpoint inhibitors and the potential opportunity to generate de novo immune responses and/or amplify existing anti-tumor T cell responses in order to improve the depth and durability of clinical responses.

Our Phase 1/2 Trial of “Off-the-Shelf,” Shared Neoantigen Immunotherapy Candidate, SLATE (GO-005)

The IND for SLATE was cleared by the U.S. Food and Drug Administration (the “FDA”) in August 2019. GO-005, a Phase 1/2 trial, began enrolling patients in August 2019. Based on the importance of KRAS as a shared neoantigen, GO-005 is focused on enrolling patients with advanced MSS colorectal cancer, lung adenocarcinoma and pancreatic ductal adenocarcinoma in whom KRAS mutations are common. A fourth cohort of potentially eligible patients consists of those with any type of tumor that harbors one of the driver mutations encoded in the SLATE cassette. The key to appropriate utilization of the “off-the-shelf” product candidate is to accurately identify patients whose tumors contain at least one of the TSNA represented within the SLATE neoantigen cassette. The widespread use of tumor mutation panel sequencing in advanced cancer has enabled the routine identification of such patients, and complementary assessment of a patient’s HLA type is a standard clinical test, performed using a simple blood draw, and completed within 7-10 days by a clinical immunology laboratory.

The Phase 1 portion of our Phase 1/2 trial has now completed enrollment and we identified a dose for further investigation in the ongoing Phase 2 portion and to evaluate safety, tolerability and, importantly, immunogenicity of our lead product candidate. In Phase 1, patients have received an initial administration of ChAdV as a prime at a fixed dose of 10¹² viral particles throughout the study, succeeded by multiple dose levels of SAM boosts (heterologous prime-boost). Dose levels of SAM start at 30 mg (Dose Levels 1 and 2) and are escalated to 100 mg (Dose Level 3) and to 300 mg (Dose Level 4). All patients receive anti-PD-1 intravenously throughout the study at the approved label dose (480 mg every 4 weeks). Co-administration of a fixed, low dose of 30 mg of subcutaneous anti-CTLA-4 with ChAdV prime and SAM boosts has been initiated once Dose Level 1 has been cleared. The rationale for earlier introduction of ipilimumab in SLATE’s dose-escalation scheme is to optimize T cell activation and proliferation at the lowest dose of SAM and account for the fact that only one TSNA may give rise to CD8+ T cells in SLATE patients compared to GRANITE’s multiple, personalized TSNAs.

The manufacturing of the SLATE product is carried out using our current supply chain. The “off-the-shelf” design of the SLATE product allows us to leverage our processes developed for personalized products.

As of July 6, 2020, 19 patients were enrolled in the Phase 1 portion of the Phase 1/2 study. Patients were 33 to 83 years of age (mean 58 years). Six patients had NSCLC, all of whom have previously been exposed to an anti PD-1 mAb. Six patients had MSS-

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CRC, five had pancreatic adenocarcinoma, one had ovarian adenocarcinoma and one had ampullary adenocarcinoma. Cumulated doses across patients included 19 doses of ChAdV, 39 doses of SAM, 58 doses of nivolumab and 47 doses of ipilimumab. Overall, the safety findings as of July 6, 2020 were consistent with reversible, acute phase immune reaction including fever and injection site reactions. No dose-limiting toxicities were observed as of December 31, 2020. A summary of demographics and safety observations are presented below in Table 2.

Table 2. Interim Phase 1 data showed GRANITE (and SLATE) prime/boost immunotherapy in combination with nivolumab was well tolerated with adverse events indicative of an inflammatory response

As of the cutoff date, SLATE patients developed CD8+ T cells against multiple KRAS driver mutations but strong responses were observed only in a subset of patients (Figure 18). Patients with NSCLC, all of whom had progressed on prior immunotherapies, had the largest degree of CD8+ T cell development. The focus of our SLATE Phase 1/2 study is now with patients with advanced NSCLC (Figure 19). Based on these observations, we are developing an optimized KRAS-focused SLATE product candidate which will replace the initial product candidate in the ongoing Phase 2 portion of our Phase 1/2 study in the first half of 2021. The single-arm Phase 2 expansion cohort was initiated in the fourth quarter of 2020 and includes patients with advanced NSCLC with relevant KRAS mutations who have progressed on prior immunotherapy, and patients with tumors where a relevant TP53 mutation exists. Additional safety and efficacy data will be presented once data has matured.

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Figure 18. CD8+ T cells are consistently induced against multiple KRAS driver mutations, but strong responses are observed only in a subset of patients.

Figure 19. Patients with NSCLC, all of whom had progressed on prior IO appear to have the largest degree of clinical benefit.

Our Phase 1/2 Trial of Personalized Immunotherapy candidate, GRANITE (GO-004)

In September 2018, our IND for our “N of 1” product candidate, GRANITE, was cleared by the FDA, and in December 2018, the FDA granted Fast Track designation to GRANITE for the treatment of colorectal cancer. In the fourth quarter of 2018, we initiated our first-in-human, Phase 1/2 trial, which we refer to as GO-004, with investigation of intramuscular heterologous prime-boost immunization with ChAdV and SAM in combination with mAb to PD-1 and CTLA-4. Our Phase 1/2 trial is actively enrolling newly diagnosed, advanced lung, gastro-esophageal and bladder cancer patients who are receiving first-line chemotherapy treatment. Production of the immunotherapy takes place while patients are receiving their initial chemotherapy. Patients subsequently receive our experimental, personalized immunotherapy candidate in checkpoint inhibitors as either maintenance therapy or second-line therapy. Patients with relapsed colorectal cancer patients with MSS tumors have trivial responses to current immunotherapies (Le at al., New England Journal of Medicine (2015)) and are also eligible combination with for GO-004 if their tumor has been predicted to have adequate TSNA to merit inclusion in our program using our EDGE model. We exclude patients who have large mutational loads and

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are well served by currently approved immunotherapy, such as melanoma patients and those with colorectal cancer with microsatellite instability. The Phase 1 portion of our Phase 1/2 trial has established a dose for further investigation in the Phase 2 portion and evaluated safety, tolerability and, importantly, immunogenicity of GRANITE. In the fourth quarter of 2020, we advanced into Phase 2 expansion cohorts. The Phase 2 portion of the GRANITE Phase 1/2 study includes a cohort for patients with MSS-CRC who have progressed on FOLFOX/FOLFIRI therapy and a second cohort for patients with GEA who have progressed on chemotherapy.

We believe co-administration of checkpoint inhibitors with personalized immunotherapy is a rational way to augment the T cell response and potential efficacy of the therapeutic regimen. Use of mAb to PD-1 is believed to unleash T cells which have been functionally silenced in tumor tissue by local PD-1 expression. Administration of antagonistic mAb to CTLA-4, an early inhibitory marker of T cell activation, has been shown to broaden the T cell response. Local subcutaneous administration of anti-CTLA-4 provides high drug concentration in the vaccination site-draining lymph node while minimizing systemic exposure, which we believe will optimize the benefit-risk ratio of our experimental regimen. Nivolumab, an anti PD-1 mAb, and ipilimumab, an anti CTLA-4 mAb, are provided by our collaborator, BMS.

Patients in the Phase 1 portion of our Phase 1/2 trial receive an initial administration of ChAdV as a prime at a fixed dose of 10¹² viral particles throughout the study, succeeded by multiple dose levels of SAM boosts (heterologous prime-boost). Dose levels of SAM start at 30 mg (Dose Level 1) and are escalated to 100 mg (Dose Levels 2 and 3) and to 300 mg (Dose Level 4), safety signals permitting. All patients receive anti-PD-1 intravenously throughout the study at the approved label dose of 480 mg every 4 weeks. Co-administration of a fixed, low dose of 30 mg of subcutaneous anti-CTLA-4 with ChAdV prime and SAM boosts has been initiated once Dose Level 2 has been cleared. A total of 8 boosts are planned.

The Phase 1 portion of GO-004 evaluated the safety, tolerability, dose, immunogenicity and preliminary efficacy of the combination of the immune checkpoint inhibitors nivolumab and ipilimumab with GRANITE.

As of July 6, 2020, 10 patients were enrolled in the Phase 1 portion of our Phase 1/2 study. Enrolled patients were aged 38 to 76 years (mean 59 years). Tumor types included NSCLC (five patients), MSS-CRC (four patients) and GEA (three patients). One patient was previously been exposed to an anti PD-1 mAb. Cumulated doses across patients included 11 doses of ChAdV, 44 doses of SAM, 61 doses of nivolumab and 14 doses of ipilimumab. Overall, the safety results as of the cutoff date were consistent with reversible, acute phase immune reaction encompassing fever (including one patient with two transient Grade 2 severe adverse events), injection site reactions and skin rashes. One patient presented with self-limiting asymptomatic Grade 3 creatinine kinase elevation of unknown etiology. No dose-limiting toxicities were observed. Summary of demographics and safety observations are presented in Table 2 above.

As of January 2021, immunogenicity data was available for seven of the eight patients treated at Dose-Levels 1 to 4. Overnight IFNg ELISpot assays against each patient’s own 20 TSNA showed neoantigen-specific CD8+ T cell responses two to four weeks after priming that were further enhanced with subsequent boosts to levels ranging from 100 to 3,000 spots/10⁶ PBMCs. Broad polyfunctional CD8+ T cell responses to multiple neoantigens were observed, including de novo priming of T cells (Figure 20). In one Dose-Level 3 patient with MSS-CRC, we observed a decrease of some metastatic lung and liver lesions concomitant with normalization of liver enzymes and of the carcinogen embryogenic antigen (“CEA”), a biomarker often elevated in patients with colorectal cancers. We also observed in this patient a reduction of circulating tumor DNA (“ctDNA”), a more specific albeit experimental biomarker specific to this patient's tumor (Figures 21-23).

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Figure 20. Strong neoantigen-specific CD8+ T cell responses to multiple neoantigens are consistently induced across all patients using an ex vivo (overnight) ELISpot assay with short peptides

Figure 21. Several patients continue experimental treatment beyond apparent radiologic progression

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Figure 22. Clear evidence of clinical benefit in a patient with MSS-CRC (Patient G8, Dose-Level 3)

Figure 23. Lung CT shows transient lesion expansion at week 8 (possible T cell infiltration) then contraction (Patient G8, Dose-Level 3)

Additional immunogenicity, safety and preliminary efficacy data will be presented once data has matured.

We hypothesize that personalized immunotherapy should ideally be administered in earlier lines of treatment, in the context of minimal residual disease and an optimal immune system. Depending on the safety profile observed during the Phase 1 portion of GO-004 and in parallel to single-arm cohort expansions in the Phase 2 portion of GO-004, we are considering options to conduct Phase 2 trials in earlier lines of treatment where our personalized immunotherapy candidates would be used as consolidation following first-line therapy. Likewise, in patients with tumors at very high risk of relapse following complete surgical resection, we may use our personalized immunotherapy candidate in the adjuvant setting with the goal of preventing recurrence of their disease. In this particularly challenging setting, we plan to use circulating tumor DNA, or ctDNA, to detect the presence of remaining tumor cells

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following surgery and during adjuvant immunotherapy. We believe ctDNA technology will soon be accepted by investigators and health authorities as a validated surrogate endpoint of efficacy alongside well-established clinical endpoints, such as metastasis-free survival, recurrence/progression-free survival and overall survival. We believe the specific risk-benefit profile of patients with localized, high-risk disease will likely require discussion with health authorities based on the outcome of the Phase 1 portion of our GO-004 study. Therefore, we expect to initiate our randomized Phase 2 adjuvant study in the second half of 2021.

Bispecific antibodies

Antibodies are an important component of immune defense against disease. The most common antibody type in humans, immunoglobulin G, or IgG, evolves within a human/patient and bears two identical arms to recognize its specific target. In contrast to monoclonal antibodies, bispecific antibodies employ different antigen specificities within the two arms—one arm recognizes a tumor antigen and the other recognizes immune-effector cells. We are developing bispecific antibodies using an anti-tumor TCR-mimetic antibody arm in the form of a Fab or a single chain antibody fragment, or scFv, as the tumor-binding domain of a bispecific antibody, thus generating a suite of bispecific antibodies capable of engaging our novel targets identified by the EDGE platform, as illustrated by Figure 24 below.

Figure 24. Schematic representation of monoclonal antibodies and two exemplary bispecific formats.

In the above figure, variable domains are indicated as well as constant domains. Heavy chain and light chain variable domains come together to form the antigen binding fragment. A schematic of an alternative engineered version of this single-chain variable fragment, or scFv, is shown. Bispecific molecules are shown comprised of normal antibody polypeptide chain pairing as well as an example incorporating a scFv for one specificity. All of our peptide-HLA TCR-mimetic antibodies were initially identified as scFv fragments, and they can be readily formatted as these modular binding domains or as normal antibody binding arms.

While many different bispecific antibody formats have been described, no single platform has emerged as an optimal solution for all targets or therapeutic applications. Rather, “rules” governing optimal activity are determined empirically for a given target pair. We are working to determine whether this target class has shared rules for optimal formatting, and we are converging on a favored format. Critical parameters include number of binding sites for each target, spacing among the binding sites, and engineered or inherent properties to drive optimal serum half-life. Affinity for each target, as well as where specifically the bispecific antibody binds each target (epitope) are also important characteristics. We have built the capability to generate large numbers of lead candidate combinations employing our TCR mimetic antibodies formatted as scFv or as traditional antibody arms and combined with a variety of distinct targeting arms. Additionally, we are developing critical assays to evaluate the safety and potency of novel candidates. Finally, we are deploying state of the art development and formulation techniques to ensure selection of candidates with robust drug-like properties for investigation. We believe these capabilities will allow efficient selection of candidates to move forward through the optimization process.

We have generated a variety of TCR-mimetic antibodies as bispecifics with different TCR-targeting arms and have obtained encouraging in vitro proof of concept data, including binding and killing of cells displaying the peptide-HLA target.

One of our most advanced programs targets CT83 peptide-HLA complexes on tumor cells that are present with high prevalence in esophageal, gastric adenocarcinoma, lung adenocarcinoma and lung squamous tumors. The optimized molecule is a 2+1 antibody that is comprised of two binding sites to the tumor target and one binding site to the CD3 on immune-effector cells. This advanced lead molecule is designed to bind specifically to the target peptide-HLA complex, but not to predicted off-target peptides. Each tumor binding site has an affinity in the range of low to sub-nM and a combined avidity in the low pM range. Molecular

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assessment data revealed a stable molecule with drug-ability properties. Its observed half-life in Tg32 mice predicted a human half-life comparable to most IgGs. Our lead molecule showed cytotoxic activity at a broad range of target density, potentially able to kill tumors containing a low target copy number/cell. Figure 25 below shows killing of cells in vitro having 30,000, 4,500 or 500 target copies/cell by our lead bispecific antibody.

Figure 25. Cytotoxic activity of lead TCR-mimetic bispecific observed in vitro.

The above figure shows the in vitro cytotoxic activity of our lead bispecific antibody directed against a CT83 peptide-HLA complex presented on tumor cells at different target densities (30,000, 4,500 and 500 copies/cell). Briefly, cells expressing CT83 and luciferase were plated at 5x104 cells/well in a 96 well plate, incubated for 3 hours for adhesion to the plate, human T cells added at a ratio of 5:1 effector to target cell. Bispecific antibody was added at various concentrations. Cultures were incubated for 3 days. Luciferase signal was assessed using Promega’s Bio-Glo assay and read on SpectraMax. Signal was normalized to control wells to determine percent of cytotoxicity.

While we advance our preclinical candidates towards manufacturing and ultimately the clinic, we also consider partnering. We recognize several advantages to partnering, including experience with proprietary effector targeting arms, experience with CMC, and assays for selection of ideal candidates. By pursuing both internal and external paths, we intend to maximize opportunities to rapidly advance to the clinic as well as to retain internal value and position for Gritstone.

Our EDGE Antigen Identification Engine—Beyond Tumor-Specific Neoantigens

Our EDGE antigen discovery platform has also identified novel, functionally tumor-specific antigens which, as opposed to most TSNA, are commonly shared between patients. A leading set of shared tumor antigens derives from cancer testis antigens, or CTA, genes that are non-mutated and normally only expressed in the testis, but which can also be expressed by some tumor tissue. The testis is an immune privileged site such that it is able to express antigens without eliciting an immune response. CTA are well established in the literature and our approach has identified many genes, and antigens from within those genes, that may represent novel shared-tumor antigens. Currently, tumor-specific CTA targets are limited; known HLA/peptide CTA are present in only a fraction of patients within any given tumor type, with some tumor types exhibiting essentially no HLA/peptide targets available in the public domain. We believe our EDGE platform has the potential to unlock these tumor types for therapeutic development by providing novel cancer immunotherapy targets that may be exploited via several therapeutic modalities.

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We are developing TCRs and antibodies that specifically recognize these novel shared tumor-specific antigens and their corresponding HLA surface proteins. These targets can be addressed therapeutically using several different formats, such as adoptive T cell therapy, bispecific antibody approaches and vaccination. These programs are in early development. Our TSNA and shared tumor antigen discovery programs are shown in Figure 26 below.

Figure 26. Our TSNA and Shared Tumor Antigen Discovery Programs

TCR-Mimetic Antibodies

While TCRs are the natural biological recognition elements on T cells for a particular HLA/peptide complex, it is possible to identify antibodies that bind with high affinity and selectivity to a particular HLA/peptide complex (Dubrovsky et al, OncoImmunology (2016)). These have been termed TCR-mimetic antibodies. Working with a third-party contract research organization, or CRO, we have screened a highly diverse bacteriophage display library, and identified TCR-mimetic antibodies against several novel CTA HLA/peptide complexes that were identified by our proprietary EDGE platform.

During the isolation process, the library was negatively selected against a panel of closely-related peptide-HLA complexes. We identify closely-related peptides, then use EDGE to predict those potential off-target liabilities that are most likely to be displayed. As a result, we identify highly specific leads without cross-reactivity to closely related structures. The candidate antibodies identified bear many properties that make them attractive entities to move forward as components of lead biologic drugs. First, they are directed against highly tumor-specific targets, allowing development of selective drugs designed to bind only to tumor, leaving normal tissues untouched. Second, the leads exhibit good affinity, which we have further improved by directed evolution approaches as part of lead optimization. The library was comprised of single-chain versions of antibody variable domains (“scFv”), responsible for antigen binding. scFvs are ideal modular building blocks for combining multiple specificities into a single molecule.

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Figure 27. Comparison of one of Gritstone’s proprietary TCR-mimetic antibody in complex with peptide-HLA with a published TCR in complex with its cognate peptide-HLA (same HLA haplotype).

As indicated in the above figure, there are many striking similarities between the TCR-mimetic antibody and the TCR recognizing their MHC/peptide complexes, including footprint, angle of interaction, and overall surface area covered.

We have carefully defined the exact nature of TCR-mimetic antibody binding to peptide-HLA target antigens. We have individually altered each amino acid in the peptide (in the peptide-HLA complex) to establish the specificity of TCR-mimetic binding. We have also defined the footprint of TCR-mimetic antibody binding on its target using both (a) X-ray crystallography (direct visualization of binding) and (b) a “protection” assay whereby antibody binding to its target physically protects target structures from chemical modification. Figure 27 above shows the high-resolution structure of one target peptide-HLA molecule in complex with one of our lead antibodies. The footprint and angle of interaction are strikingly similar between the TCR mimetic antibody and a published structure of a typical TCR bound to its cognate HLA/peptide complex. Multiple TCR-mimetic leads have been identified against a set of target HLA/peptide complexes for tumor-specific targets identified by our proprietary EDGE platform, that bind, similarly to the natural TCR interaction, with high affinity and specificity. We believe these candidates are an ideal starting point for building a portfolio of bispecific antibody leads.

T Cell Receptors

TCRs recognize HLA/peptides, and once we have identified CTA-derived peptides plus their HLA binding partner as tumor-specific antigens, we can proceed to the identification of matched TCRs. This is performed using healthy HLA-matched donors as a source of diverse T cells and screening these T cells against the target HLA/peptides. T cells that activate and expand in response to a target HLA/peptide will express relevant TCRs, and these can be characterized by isolation of the relevant T cells and sequencing of their TCR genes. These natural TCRs may offer advantages over alternative TCR identification approaches. We possess the internal expertise to identify HLA/peptide specific TCRs from HLA-matched donor blood or from vaccinated cancer patients, and we may partner those TCRs with established adoptive T cell therapy companies.

New Developments

COVID-19 Program (CORAL)

Gritstone is advancing development of a second-generation vaccine candidate against SARS-CoV-2, the virus that causes COVID-19, designed to provide prolonged protection and potency against Spike mutants. Gritstone and NIAID, part of the National Institutes of Health, have entered into a clinical trial agreement to initiate clinical testing. We are collaborating on a Phase 1 clinical

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trial to be conducted through the NIAID-supported IDCRC. The IND has been approved, and volunteer subjects enrollment will start imminently. The Gates Foundation is supporting the preclinical evaluation of the vaccine candidate. Through a license agreement with LJI, one of the leading global organizations dedicated to studying the immune system, Gritstone has access to validated SARS-CoV-2 epitopes that have been identified through LJI’s studies of hundreds of patients recovering from COVID-19. Using these epitopes and the company’s proprietary Gritstone EDGE^TM and vaccine platform technologies, Gritstone is developing a novel vaccine candidate against COVID-19, containing Spike (similar to first generation vaccines) but also additional viral epitopes that offer potential targets for T cell immunity. Gritstone uses both self-amplifying mRNA and adenoviral vectors in an effort to deliver the SARS-CoV-2 viral antigens. Our preclinical work has shown that our SARS-CoV-2 vaccines induced sustained, high-titer neutralizing antibodies and T cell responses (Figure 28). As well as a potential role in protection against SARS-CoV-2, the notion of using evolutionarily conserved viral antigens (in addition to Spike) as the basis for a vaccine candidate that is designed to induce antibody and T-cell responses to provide protection against future coronavirus pandemics is an exciting concept that springs from our current work.

Figure 28. Heterologous Prime/Boost Drove Potent and Durable Immune Responses in Mice

License and Collaborations

HIV Vaccine in Collaboration with Gilead.

In February 2021, we announced that we had entered into a collaboration, option and license agreement with Gilead to research and develop a vaccine-based immunotherapy for HIV infection. Together, we will develop an HIV-specific therapeutic vaccine using Gritstone’s proprietary prime-boost vaccine platform, comprised of SAM and adenoviral vectors, with antigens developed by Gilead. Under the terms of the agreement, Gilead invested $60.0 million, consisting of a $30.0 million upfront cash payment to us within 30 days of closing and a $30.0 million equity investment at a premium at closing. Gilead will be responsible for conducting a Phase 1 study for the HIV-specific therapeutic vaccine and holds an exclusive option under the collaboration to obtain an exclusive license to develop and commercialize the HIV-specific therapeutic vaccine beyond Phase 1. Gritstone is also eligible to receive up to an additional $725.0 million if the option is exercised and if certain clinical, regulatory and commercial milestones are achieved, as well as mid single-digit to low double-digit tiered royalties on net sales upon commercialization.

Strategic Collaboration with bluebird bio

In August 2018, we entered into a research collaboration and license agreement with bluebird bio, Inc., or bluebird, to utilize our EDGE platform to identify and validate tumor-specific targets and provide TCRs directed to 10 selected targets for use in bluebird’s cell therapy platform. Under the collaboration, we received a non-refundable up-front cash payment of $20.0 million and an additional $10.0 million in equity investment in our Series C convertible preferred stock. We are also eligible to receive up to an aggregate of $1.2 billion in development, regulatory and commercial milestones associated with bluebird bio’s resulting cell therapy products, as well as tiered, single-digit royalties on sales of the TCR immunotherapy products that utilize the TCRs discovered by us. The royalty term for each TCR immunotherapy product shall be determined on a product-by-product and country-by-country basis

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and will commence on the first commercial sale of each product in a country and end on the latest of: (i) expiration or termination of the last to expire valid claim of the last licensed patent that covers the product pursuant to the agreement; (ii) expiration of all periods of regulatory exclusivity for the product in such country (in respect of sales in that country); and (iii) 10 years after the first commercial sale of such product in such country (in respect of sales in that country). bluebird will be solely responsible for all costs and expenses of its development, manufacturing, and commercial activities for resulting therapies.

The identification, validation, selection and development of the TCRs will be conducted during an estimated 5-year research term and may be extended by an additional year under certain conditions. The collaboration will be governed by a joint steering committee with representatives from us and bluebird. We and bluebird have exchanged non-exclusive licenses to carry out the research program, and, on a selected target-by-selected target basis, we have granted bluebird an exclusive worldwide license to research, develop, and commercialize resulting cell therapy products directed to such targets, including rights to utilize TCRs discovered by us. The collaboration term ends on a country-by-country and product candidate-by-product candidate basis based on completion of all payments owed to us by bluebird thereon. Either party may terminate the agreement upon written notice to the other party in the event of the other party’s uncured material breach, subject to a dispute resolution process. In addition, bluebird may terminate the agreement for convenience upon prior written notice to us.

License Agreement with Arbutus Biopharma Corporation

In October 2017, we executed a license agreement with Arbutus Biopharma Corporation (“Arbutus”). Certain terms of the agreement were modified by amendment in July 2018. Arbutus is a leader in LNP technology with a broad intellectual property estate and a large library of LNPs, including multiple LNPs being used in clinical development by its partners, as well as the chemistry expertise to synthesize novel LNPs with properties optimal for SAM.

Under the agreement, Arbutus grants us a worldwide, exclusive (even as to Arbutus, subject to certain limited exceptions), sublicensable, transferable license, to research, develop, manufacture, and commercialize our novel RNA-based platform for intracellular delivery of SAM encoding TSNA in combination with one or more of Arbutus’ proprietary LNPs. The licensed technology includes Arbutus’ portfolio of proprietary and clinically validated LNP products and associated intellectual property and includes technology transfer of Arbutus’ manufacturing know-how.

As part of our collaboration, we have identified an LNP formulation that we believe will be optimal for use in our Phase 1/2 clinical trial of GRANITE and SLATE. This LNP formulation is currently being used by third parties in human clinical trials in the United States. We have also initiated an effort to screen Arbutus’ library of LNPs and evaluate novel LNPs to potentially identify an LNP that increases the potency of our SAM platform further. Our goal is to deliver a second-generation SAM immunotherapy that has the potential to serve as a homologous prime-boost immunotherapy.

Under the license agreement, we paid Arbutus an upfront payment of $5.0 million. We have also agreed to make aggregate payments of up to $73.5 million upon the achievement of specified development milestones for up to three products, and an aggregate $50.0 million in commercial milestone payments, as well as royalty payments in the low single-digits on net sales of licensed products for a royalty term lasting until the expiration of the last patent covered under the license. The last-to-expire patent is currently scheduled to expire on November 10, 2030. Pending applications will nominally expire 20 years after the filing date of the first utility application to which they claim priority. Following acceptance of our first IND in September 2018, we made the first milestone payment of $2.5 million to Arbutus. In August 2019, a milestone was met following the initial patient treatment of SLATE in our GO-005 clinical trial. We recorded $3.0 million as research and development expense in connection with the milestone. The milestone payment was made in October 2019. Further milestone payments are not expected to occur before 2021. In addition, we will reimburse Arbutus for conducting technology development and providing manufacturing and regulatory support for our product candidates.

The Arbutus license continues in effect until the last to expire royalty payment or early termination. The license is terminable by us for convenience with 60 days prior written notice, upon payment of a no-cause termination sum. We may also terminate in the event of material adverse safety data for a product, failure to achieve a primary or secondary efficacy endpoint, or if a regulatory authority takes action that prevents us from commercializing any product. Either party may terminate the agreement for material breach, and Arbutus may terminate the agreement for abandonment or if we challenge Arbutus patents.

Manufacturing

Manufacturing is a vital component of our personalized immunotherapy platform, and we are devoting significant resources to manufacturing and process development in an effort to maintain the potential safety and efficacy of our product candidates, as well as to reduce our per-unit manufacturing costs and time to market. The production of our personalized immunotherapy candidates requires

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two distinct elements for each patient: tumor biopsy analysis to determine candidate neoantigens, followed by manufacture of vectors containing a personalized cassette encoding the selected neoantigens. SLATE contains a fixed cassette with TSNA that is shared across a subset of cancer patients rather than a cassette unique to an individual patient, which is designed to provide an off-the-shelf alternative to our personalized manufactured product candidate, GRANITE. The manufacture of these vectors involves complex processes, including per-patient plasmid production, mammalian cell production of virus and RNA synthesis and lipid encapsulation. SLATE manufacturing, as a fixed, “off-the-shelf” product candidate, is not time-sensitive and is relatively straightforward operationally. GRANITE, on the other hand, is an “N of 1” product candidate and is manufactured in real-time for each patient, which involves a greater logistical burden.

Our near-term goal is to carefully manage our fixed-cost structure, maximize optionality, and drive long-term cost of goods as low as possible. We have used a hybrid approach to manufacturing our personalized immunotherapy candidates whereby certain elements of our product candidates are manufactured on an outsourced basis at CMOs, and other elements of our product candidates are manufactured internally at the 42,600 square foot manufacturing facility we established in 2017 in Pleasanton, California, all designed in compliance with cGMP. We have leveraged our relationships with CMOs for preclinical studies and Phase 1/2 clinical trial supply. Doing so has significantly accelerated our ability to advance clinical trials, gain insights into the multiple manufacturing processes and establish an infrastructure for future trials.

Our manufacturing process begins with receipt of a patient’s routine biopsy and blood sample at our Cambridge, Massachusetts facility, where TSNA identification is performed using the EDGE platform. The TSNA sequences generated by our platform are sent electronically to a synthetic biology CMO to generate the patient-specific TSNA cassette, which is then cloned into each of the ChAdV and SAM vectors and amplified. Following amplification, the ChAdV vector containing the cassette is sent to our Pleasanton, California facility for ChAdV manufacture and production into vials. In parallel, the SAM vector until recently was sent to another CMO for RNA manufacture and then to a final CMO for formulation into LNP and production into vials. Currently, the entire manufacturing process, from biopsy receipt at Gritstone to the release and shipment of the personalized immunotherapy candidate to the clinical site for patient administration, takes approximately 16-20 weeks in principle. We expect this production and release timeline (and associated cost) will diminish over time due to process scaling, potential improvements in production and testing technologies and internal process expertise, internalizing production as well as potential reductions in regulatory testing requirements based on clinical experience.

To achieve this, our process development group is focused on several key initiatives. The first is investigating novel approaches to manufacturing our products, including process optimization and quality by design of each intermediate, drug substance and drug product. Additionally, we are systematically characterizing our manufacturing processes, including product intermediates and manufacturing unit operations. This characterization effort will allow us to implement process changes over the entire product lifecycle and to quickly react to evolving process technologies that can lead to reductions in per-unit manufacturing costs and shorter process cycle times. In addition, we plan to establish automated, closed-platform manufacturing processes. Such processes should give us the ability to conduct manufacturing in a lower-classified, lower cost manufacturing environment for multiple steps of our drug product manufacturing.

Our medium-term goal is to internalize the majority of the manufacturing steps to drive down both cost and production time, as well as establish full control over intellectual property and product quality. In 2020, we continued to build the internal capability to manufacture our products entirely using internal facilities and staff. We continue efforts toward the phased integration of all manufacturing into our Pleasanton, California biomanufacturing facility. The ChAdV prime production is already fully integrated into the Pleasanton facility and we have largely completed integrating the plasmid and the SAM boost production in-house. We believe that operating our own manufacturing facility will provide us with enhanced control of material supply for both clinical trials and the commercial market, will enable the more rapid implementation of process changes, and will allow for better long-term margins. Although we have developed these capabilities, we will assess which aspects will continue to be outsourced, and these may change over time.

For Gritstone’s recent COVID-19 (CORAL) program, manufacturing of early-stage clinical lots was initiated on our Pleasanton, California manufacturing facility towards the end of 2020. Product candidates include both self-amplifying mRNA and adenoviral vectors to deliver the SARS-CoV-2 viral antigens. Additional scale up activities involving CMOs will be needed as the CORAL program progresses leading to large demand for the product candidates.

Our manufacturing strategy is currently structured to support our U.S., E.U. and Australian development plans. We believe this manufacturing strategy developed for global distribution will enable use in other geographies. Specific supply strategies for other geographies will be developed as part of our clinical and commercial plans for such other geographies.

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Commercialization Plan

Gritstone does not currently have any approved therapies, and we do not anticipate receiving marketing authorization for our early development candidates in either the United States or other worldwide regions in the near future. An internal expansion of sales, marketing, and commercial distribution capabilities would be developed once Gritstone has obtained clinical data that can support licensure following discussions with the FDA or other worldwide health authorities. If and when any of our development candidates are approved for commercialization, an infrastructure to support ongoing sales in the United States and possibly in some other regions will be created.  

Competition

The biotechnology and pharmaceutical industries put significant emphasis and resources into the development of novel and proprietary therapies for treatment of cancer and infectious disease. We face substantial competition from many different sources, including large and specialty pharmaceutical and biotechnology companies, academic research institutions and governmental agencies and public and private research institutions. We anticipate that we will continue to face increasing competition in our field as new therapies, technologies, and data emerge.

In addition to the current standard of care for patients, commercial and academic clinical trials are being pursued by a number of parties in the field of immunotherapy. Results from these trials have fueled continued interest in immunotherapy, and our competitors include:

Many of our competitors, either alone or with their strategic partners, have significantly greater financial resources and expertise in research and development, manufacturing, preclinical testing, conducting clinical trials, and marketing approved products than we do. Mergers and acquisitions in the pharmaceutical, biotechnology and gene therapy industries may result in even more resources being concentrated among a smaller number of our competitors. Smaller or early-stage companies may also prove to be significant competitors, particularly through collaborative arrangements with established companies. These competitors also compete with us in recruiting and retaining qualified scientific and management personnel and establishing clinical trial sites and patient registration for clinical trials, as well as in acquiring technologies complementary to, or necessary for, our programs.

Our commercial opportunity could be reduced or eliminated if our competitors develop and commercialize products that are safer, more effective, have fewer or less severe side effects, are more convenient or are less expensive than any products that we may develop. Our competitors also may obtain FDA or other regulatory approval for their products more rapidly than we may obtain approval for ours, which could result in our competitors establishing a strong market position before we are able to enter the market. The key competitive factors affecting the success of all of our programs are likely to be their efficacy, safety, cost and convenience.

Intellectual Property

Our commercial success depends in part on our ability to obtain and maintain proprietary protection for our products and services, to operate without infringing the proprietary rights of others, and to prevent others from infringing our proprietary rights. We rely on a combination of patents and trade secrets, as well as contractual protections, to establish and protect our intellectual property rights. We seek to protect our proprietary position by, among other things, filing patent applications in the United States and internationally. Our patent estate includes patent applications with claims relating to our products, methods, and manufacturing processes, and broader claims for potential future products and developments. As of December 31, 2020, our solely-owned patent portfolio includes, on a worldwide basis, pending patent applications and issued patents relating to our products, methods, and manufacturing processes.

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As of December 31, 2020, our solely-owned patent estate includes a portfolio of pending patent applications related to our neoantigen-based platform; a portfolio of pending patent applications related to our infectious disease-based platform, including our bispecific antibody platform and TCRs. Details regarding these portfolios are provided below.

As of December 31, 2020, our solely-owned patent portfolio related to our neoantigen-based platform includes domestic and international patent rights with claims related to neoantigen identification and related uses and manufacture. Any patents that may issue from these pending patent applications are expected to expire between 2036 and 2042, absent any patent term adjustments or extensions.

As of December 31, 2020, our solely-owned patent portfolio related to our shared antigen-based platform, including our bispecific antibody platform and TCRs, includes domestic and international patent rights with claims related to shared antigens, shared antigen-binding proteins, and their related uses and manufacture. Any patents that may issue from these pending patent applications are expected to expire between 2038 and 2042, absent any patent term adjustments or extensions. In addition, in the ordinary course of our business, we also enter into agreements with other third parties for non-exclusive rights to intellectual property directed to other technologies that are ancillary to our business, including laboratory information management software and research and development tools.

In addition to patents, we have filed for trademark registration with the United States Patent and Trademark Office, or the USPTO, as well as certain other international trademark agencies, for “GRITSTONE,” “GRANITE,” “SLATE” and our logo. Furthermore, we rely upon trade secrets, know-how and continuing technological innovation to develop and maintain our competitive position.

In some instances, we submit patent applications directly with the USPTO as provisional patent applications. Provisional applications for patents were designed to provide a lower-cost first patent filing in the United States. Corresponding non-provisional patent applications must be filed not later than twelve (12) months after the provisional application filing date. The corresponding non-provisional application benefits in that the priority date(s) of the patent application is/are the earlier provisional application filing date(s), and the patent term of the finally issued patent is calculated from the later non-provisional application filing date. This system allows us to obtain an early priority date, add material to the patent application(s) during the priority year, obtain a later start to the patent term and to delay prosecution costs, which may be useful in the event that we decide not to pursue examination in an application. We file U.S. non-provisional applications and Patent Cooperation Treaty, or PCT, applications that claim the benefit of the priority date of earlier filed provisional applications, when applicable. The PCT system allows a single application to be filed within twelve (12) months of the original priority date of the patent application, and to designate PCT member states in which national patent applications can later be pursued based on the international patent application filed under the PCT. The PCT searching authority performs a patentability search and issues a non-binding patentability opinion which can be used to evaluate the chances of success for the national applications in foreign countries prior to having to incur the filing fees. Although a PCT application does not issue as a patent, it allows the applicant to seek protection in any of the member states through national-phase applications.

At the end of the period of two and a half years from the first priority date of the patent application, separate patent applications can be pursued in any of the PCT member states either by direct national filing or, in some cases by filing through a regional patent organization, such as the European Patent Organization. The PCT system delays expenses, allows a limited evaluation of the chances of success for national/regional patent applications and enables substantial savings where applications are abandoned within the first two and a half years of filing.

For all patent applications, we determine claiming strategy on a case-by-case basis. Advice of counsel and our business model and needs are always considered. We file patents containing claims for protection of all useful applications of our proprietary technologies and any products, as well as all new applications and/or uses we discover for existing technologies and products, assuming these are strategically valuable. We continuously reassess the number and type of patent applications, as well as the pending and issued patent claims to ensure that maximum coverage and value are obtained for our processes, and compositions, given existing patent office rules and regulations. Further, claims may be modified during patent prosecution to meet our intellectual property and business needs.

We recognize that the ability to obtain patent protection and the degree of such protection depends on a number of factors, including the extent of the prior art, the novelty and non-obviousness of the invention, and the ability to satisfy the enablement requirement of the patent laws. The patent positions of biotechnology companies like ours are generally uncertain and involve complex legal, scientific and factual questions. In addition, the coverage claimed in a patent application can be significantly reduced before the patent is issued, and its scope can be reinterpreted or further altered even after patent issuance. Consequently, we may not obtain or maintain adequate patent protection for any of our product candidates or for our technology platform. We cannot predict whether the patent applications we are currently pursuing will issue as patents in any particular jurisdiction or whether the claims of

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any issued patents will provide sufficient proprietary protection from competitors. Any patents that we hold may be challenged, circumvented or invalidated by third parties.

Our commercial success will also depend in part on not infringing the proprietary rights of third parties. In addition, we have licensed rights under proprietary technologies of third parties to develop, manufacture and commercialize specific aspects of our products. It is uncertain whether the issuance of any third-party patent would require us to alter our development or commercial strategies, alter our processes, obtain licenses or cease certain activities. The expiration of patents or patent applications licensed from third parties or our breach of any license agreements or failure to obtain a license to proprietary rights that we may require to develop or commercialize our future technology may have a material adverse impact on us. If third parties prepare and file patent applications in the United States that also claim technology to which we have rights, we may have to participate in interference proceedings in the USPTO to determine priority of invention.

We further own trade secrets relating to our technology, and we maintain the confidentiality of proprietary information to protect aspects of our business that are not amenable to, or that we do not consider appropriate for, patent protection. We seek to protect our trade secrets and know-how by entering into confidentiality agreements with third parties, consultants and employees who have access to such trade secrets and know-how. These agreements provide that all confidential information concerning our business or financial affairs developed or made known to the individual during the course of the individual’s relationship with us are to be kept confidential and not disclosed to third parties except in specific circumstances. In addition, we enter into employment agreements that require employees to assign to us any inventions, trade secrets or know-how that they develop while employed by us. Although we take steps to protect our proprietary information and trade secrets, including through agreements with our employees and consultants, these agreements may be breached, or third parties may independently develop substantially equivalent proprietary information and techniques or otherwise gain access to our trade secrets or disclose our technology. Thus, we may not be able to meaningfully protect our trade secrets. To the extent that our employees, consultants, scientific advisors or other contractors use intellectual property owned by others in their work for us, disputes may arise as to the rights in related or resulting know how and inventions.

For a more comprehensive discussion of the risks related to our intellectual property, please see “Risk Factors—Risks Related to Intellectual Property.”

Government Regulation

The FDA and other regulatory authorities at federal, state, and local levels, as well as in foreign countries, extensively regulate, among other things, the research, development, testing, manufacture, quality control, import, export, safety, effectiveness, labeling, packaging, storage, distribution, record keeping, approval, advertising, promotion, marketing, post-approval monitoring, and post-approval reporting of biologics such as those we are developing. We, along with third-party contractors, will be required to navigate the various preclinical, clinical and commercial approval requirements of the governing regulatory agencies of the countries in which we wish to conduct studies or seek approval or licensure of our product candidates.

In the United States, the FDA regulates biologic products under both the Federal Food, Drug and Cosmetic Act and the Public Health Service Act and their respective implementing regulations. Our product candidates are subject to regulation by the FDA as biological products. Biological products require the submission of a biologics license application, or BLA, and licensure, which constitutes approval, by the FDA before being marketed in the United States. None of our product candidates has been approved by the FDA for marketing in the United States, and we currently have no BLAs pending. Failure to comply with applicable FDA or other requirements at any time during product development, clinical testing, the approval process or after approval may result in administrative or judicial sanctions. These sanctions could include the FDA’s refusal to approve pending applications, suspension or revocation of approved applications, warning letters, product recalls, product seizures, total or partial suspensions of manufacturing or distribution, injunctions, fines, civil penalties or criminal prosecution.

The process required by the FDA before biologic product candidates may be marketed in the United States generally involves the following:

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Preclinical and Clinical Development

Prior to beginning the first clinical trial with a product candidate, we must submit an IND to the FDA. An IND is a request for authorization from the FDA to administer an investigational new drug product to humans. The central focus of an IND submission is on the general investigational plan and the protocol(s) for clinical studies. The IND also includes results of animal and in vitro studies assessing the toxicology, pharmacokinetics, pharmacology, and pharmacodynamic characteristics of the product; chemistry, manufacturing, and controls information; and any available human data or literature to support the use of the investigational product. An IND must become effective before human clinical trials may begin. The IND automatically becomes effective 30 days after receipt by the FDA, unless the FDA, within the 30-day time period, raises safety concerns or questions about the proposed clinical trial. In such a case, the IND may be placed on clinical hold and the IND sponsor and the FDA must resolve any outstanding concerns or questions before the clinical trial can begin. Submission of an IND therefore may or may not result in FDA authorization to begin a clinical trial.

In addition to the submission of an IND to the FDA before initiation of a clinical trial in the United States, under the National institutes of Health, or NIH, Guidelines for Research Involving Recombinant or Synthetic Nucleic Acid Molecules, or NIH Guidelines, supervision of human gene transfer trials includes evaluation and assessment by an institutional biosafety committee, or IBC, a local institutional committee that reviews and oversees research utilizing recombinant or synthetic nucleic acid molecules at that institution. The IBC assesses the safety of the research and identifies any potential risk to public health or the environment, and such review may result in some delay before initiation of a clinical trial. While the NIH Guidelines are not mandatory unless the research in question is being conducted at or sponsored by institutions receiving NIH funding of recombinant or synthetic nucleic acid molecule research, many companies and other institutions not otherwise subject to the NIH Guidelines voluntarily follow them. Thus, companies are still subject to significant regulatory oversight by the FDA, IRBs and, if applicable, the IBC of each institution at which it conducts clinical trials.

Clinical trials involve the administration of the investigational product to human subjects under the supervision of qualified investigators in accordance with GCPs, which include the requirement that all research subjects provide their informed consent for their participation in any clinical study. Clinical trials are conducted under protocols detailing, among other things, the objectives of the study, the parameters to be used in monitoring safety and the effectiveness criteria to be evaluated. Generally, a separate submission to the existing IND must be made for each successive clinical trial conducted during product development and for any subsequent protocol amendments. Furthermore, an independent IRB for each site proposing to conduct the clinical trial must review and approve the plan for any clinical trial (including its informed consent form) before the clinical trial begins at that site, as well as monitor the study until completed. Regulatory authorities, the IRB or the sponsor may suspend a clinical trial at any time on various grounds, including a finding that the subjects are being exposed to an unacceptable health risk or that the trial is unlikely to meet its stated objectives. Some studies also include oversight by an independent group of qualified experts organized by the clinical study sponsor, known as a data safety monitoring board, which provides authorization for whether or not a study may move forward at designated check points based on access to certain data from the study and may halt the clinical trial if it determines that there is an unacceptable safety risk for subjects or other grounds, such as no demonstration of efficacy. There are also requirements governing the reporting of ongoing clinical studies and clinical study results to public registries.

For purposes of BLA approval, human clinical trials are typically conducted in three (3) sequential phases that may overlap.

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In some cases, the FDA may require, or companies may voluntarily pursue, additional clinical trials after a product is approved to gain more information about the product. These so-called Phase 4 studies may be made a condition to approval of the BLA. Concurrent with clinical trials, companies may complete additional animal studies and develop additional information about the biological characteristics of the product candidate, and they must finalize a process for manufacturing the product in commercial quantities in accordance with cGMP requirements. The manufacturing process must be capable of consistently producing quality batches of the product candidate and, among other things, must develop methods for testing the safety, purity and potency. Additionally, appropriate packaging must be selected and tested, and stability studies must be conducted to demonstrate that the product candidate does not undergo unacceptable deterioration over its shelf life.

BLA Submission and Review

Assuming successful completion of all required testing in accordance with all applicable regulatory requirements, the results of product development, nonclinical studies and clinical trials are submitted to the FDA as part of a BLA requesting approval to market the product for one or more indications. The BLA must include all relevant data available from pertinent preclinical and clinical studies, including negative or ambiguous results as well as positive findings, together with detailed information relating to the product’s chemistry, manufacturing, controls, and proposed labeling, among other things. The submission of a BLA requires payment of a substantial application user fee to the FDA unless a waiver or exemption applies.

Once a BLA has been submitted, within sixty (60) days, the FDA first reviews the BLA to determine if it is substantially complete before the agency accepts it for filing. The FDA’s goal is to review standard applications within ten (10) months after it accepts the application for filing, or, if the application qualifies for priority review, six (6) months after the FDA accepts the application for filing. In both standard and priority reviews, the review process is often significantly extended by FDA requests for additional information or clarification. The FDA reviews a BLA to determine, among other things, whether a product is safe, pure and potent and the facility in which it is manufactured, processed, packed, or held meets standards designed to assure the product’s continued safety, purity and potency. The FDA may convene an advisory committee to provide clinical insight on application review questions. Before approving a BLA, the FDA will typically inspect the facility or facilities where the product is manufactured. The FDA will not approve an application unless it determines that the manufacturing processes and facilities are in compliance with cGMP requirements and adequate to assure consistent production of the product within required specifications. Additionally, before approving a BLA, the FDA will typically inspect one or more clinical sites, as well as the sponsor, to assure compliance with GCP. If the FDA determines that the application, manufacturing process or manufacturing facilities are not acceptable, it will outline the deficiencies in the submission and often will request additional testing or information. Notwithstanding the submission of any requested additional information, the FDA ultimately may decide that the application does not satisfy the regulatory criteria for approval.

After the FDA evaluates a BLA and conducts inspections of manufacturing facilities where the investigational product will be produced, the FDA may issue an approval letter or a Complete Response Letter. An approval letter authorizes commercial marketing of the product with specific prescribing information for specific indications. A Complete Response Letter will describe all of the deficiencies that the FDA has identified in the BLA, except that where the FDA determines that the data supporting the application are inadequate to support approval, the FDA may issue the Complete Response Letter without first conducting required inspections, testing submitted product lots, and/or reviewing proposed labeling. In issuing the Complete Response Letter, the FDA may recommend actions that the applicant might take to place the BLA in condition for approval, including requests for additional information or clarification. The FDA may delay or refuse approval of a BLA if applicable regulatory criteria are not satisfied, require additional testing or information and/or require post-marketing testing and surveillance to monitor safety or efficacy of a product.

If regulatory approval of a product is granted, such approval will be granted for particular indications and may entail limitations on the indicated uses for which such product may be marketed. For example, the FDA may approve the BLA with a REMS

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to ensure the benefits of the product outweigh its risks. A REMS is a safety strategy to manage a known or potential serious risk associated with a product and to enable patients to have continued access to such medicines by managing their safe use. A REMS program may be required to include various elements, such as a medication guide or patient package insert, a communication plan to educate healthcare providers of the drug’s risks, or other elements to assure safe use, such as limitations on who may prescribe or dispense the drug, dispensing only under certain circumstances, special monitoring and the use of patient registries. The FDA also may condition approval on, among other things, changes to proposed labeling or the development of adequate controls and specifications. Once approved, the FDA may withdraw the product approval if compliance with pre- and post-marketing requirements is not maintained or if problems occur after the product reaches the marketplace. The FDA may require one or more Phase 4 post-market studies and surveillance to further assess and monitor the product’s safety and effectiveness after commercialization and may limit further marketing of the product based on the results of these post-marketing studies.

Expedited Development and Review Programs

The FDA offers a number of expedited development and review programs for qualifying product candidates. For example, the FDA granted GRANITE fast track designation for treatment of colorectal cancer in December 2018. The fast track program is intended to expedite or facilitate the process for reviewing new product candidates that meet certain criteria. Product candidates are eligible for fast track designation if they are intended to treat a serious or life-threatening disease or condition and demonstrate the potential to address unmet medical needs for the disease or condition. Fast track designation applies to the combination of the product candidate and the specific indication for which it is being studied. The sponsor of a fast track product candidate has opportunities for frequent interactions with the review team during product development. A fast track product candidate may also be eligible for rolling review, where the FDA may consider for review sections of the BLA on a rolling basis before the complete application is submitted, if the sponsor provides a schedule for the submission of the sections of the BLA, the FDA agrees to accept sections of the BLA and determines that the schedule is acceptable, and the sponsor pays any required user fees upon submission of the first section of the BLA.

A product candidate intended to treat a serious or life-threatening disease or condition may also be eligible for breakthrough therapy designation to expedite its development and review. A product candidate can receive breakthrough therapy designation if preliminary clinical evidence indicates that the product candidate may demonstrate substantial improvement over existing therapies on one or more clinically significant endpoints, such as substantial treatment effects observed early in clinical development. The designation includes all of the fast track program features, as well as more intensive FDA interaction and guidance beginning as early as Phase 1 and an organizational commitment to expedite the development and review of the product, including involvement of senior managers.

Any marketing application for a biologic submitted to the FDA for approval, including a product candidate with a fast track designation and/or breakthrough therapy designation, may be eligible for other types of FDA programs intended to expedite the FDA review and approval process, such as priority review and accelerated approval. A product is eligible for priority review if it has the potential to provide a significant improvement in the treatment, diagnosis or prevention of a serious disease or condition compared to marketed products. Sponsors may also obtain a priority review voucher upon approval of a BLA for certain qualifying diseases and conditions that can be applied to a subsequent BLA submission. Generally, priority review designation means the FDA’s goal is to take action on the marketing application within six (6) months of the sixty (60) day filing date, compared with ten (10) months under standard review.

Additionally, product candidates studied for their safety and effectiveness in treating serious or life-threatening diseases or conditions may receive accelerated approval upon a determination that the product candidate has an effect on a surrogate endpoint that is reasonably likely to predict clinical benefit, or on a clinical endpoint that can be measured earlier than irreversible morbidity or mortality, that is reasonably likely to predict an effect on irreversible morbidity or mortality or other clinical benefit, taking into account the severity, rarity, or prevalence of the condition and the availability or lack of alternative treatments. As a condition of accelerated approval, the FDA will generally require the sponsor to perform adequate and well-controlled post-marketing clinical studies to verify and describe the anticipated effect on irreversible morbidity or mortality or other clinical benefit. In addition, the FDA currently requires that during the preapproval review period, accelerated approval applicants submit for the agency’s consideration promotional materials intended for use within 120 days following marketing approval, which could adversely impact the timing of the commercial launch of the product. After 120 days following marketing approval, unless otherwise notified by the agency, accelerated approval applicants are required to submit promotional materials at least 30 days prior to intended use.

In 2017, FDA established a new regenerative medicine advanced therapy, or RMAT, designation as part of its implementation of the 21st Century Cures Act, which was signed into law in December 2016. To qualify for RMAT designation, the product candidate must meet the following criteria: (1) it qualifies as a RMAT, which is defined as a cell therapy, therapeutic tissue engineering product, human cell and tissue product, or any combination product using such therapies or products, with limited exceptions; (2) it is intended

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to treat, modify, reverse, or cure a serious or life-threatening disease or condition; and (3) preliminary clinical evidence indicates that the drug has the potential to address unmet medical needs for such a disease or condition. Like fast track and breakthrough therapy designation, RMAT designation provides potential benefits that include more frequent meetings with FDA to discuss the development plan for the product candidate and eligibility for rolling review and priority review. Products granted RMAT designation may also be eligible for accelerated approval on the basis of a surrogate or intermediate endpoint reasonably likely to predict long-term clinical benefit, or reliance upon data obtained from a meaningful number of sites, including through expansion to additional sites. Once approved, when appropriate, the FDA can permit fulfillment of post-approval requirements under accelerated approval through the submission of clinical evidence, clinical studies, patient registries, or other sources of real world evidence such as electronic health records; through the collection of larger confirmatory datasets; or through post-approval monitoring of all patients treated with the therapy prior to approval.

Fast track designation, breakthrough therapy designation, priority review, accelerated approval, and RMAT designation do not change the standards for approval but may expedite the development or approval process. In addition, even if a product candidate qualifies for one or more of these programs, the FDA may later decide that it no longer meets the conditions for designation.

Orphan Drug Designation

Under the Orphan Drug Act, the FDA may grant orphan designation to a drug or biologic intended to treat a rare disease or condition, which is a disease or condition that affects fewer than 200,000 individuals in the United States, or if it affects more than 200,000 individuals in the United States, there is no reasonable expectation that the cost of developing and making available a drug or biologic for this type of disease or condition will be recovered from sales in the United States for that drug or biologic. Orphan drug designation must be requested before submitting a BLA. If, at the time a sponsor requests orphan designation for a drug, the FDA has previously approved a drug considered the “same drug” for the same rare disease or condition, to obtain orphan designation, the sponsor must provide a plausible hypothesis of clinical superiority over the previously approved same drug. After the FDA grants orphan drug designation, the generic identity of the therapeutic agent and its potential orphan use are disclosed publicly by the FDA. The orphan drug designation does not convey any advantage in, or shorten the duration of, the regulatory review or approval process.

If a product that has orphan drug designation subsequently receives the first FDA approval for the disease for which it has such designation, meaning there is no previously approved “same drug” for the same orphan condition, the product is entitled to orphan drug exclusive approval (or exclusivity). If there is a previously approved same drug for the same orphan condition, to obtain orphan exclusivity, the sponsor of the subsequent drug must demonstrate clinical superiority over the previously approved same drug. If granted, orphan exclusivity means that the FDA may not approve any other applications, including a full BLA, to market the same drug or biologic for the same orphan indication for seven years, except in limited circumstances, such as a showing of clinical superiority to the product with orphan drug exclusivity. Orphan drug exclusivity does not prevent FDA from approving a different drug or biologic for the same disease or condition, or the same drug or biologic for a different disease or condition. Among the other benefits of orphan drug designation are tax credits for certain research and a waiver of the BLA application fee.

A designated orphan drug may not receive orphan drug exclusivity that covers the full approved indication if it is approved for a use that is broader than the indication for which it received orphan designation. In addition, exclusive marketing rights in the United States may be lost if the FDA later determines that the request for designation was materially defective or if the manufacturer is unable to assure sufficient quantities of the product to meet the needs of patients with the rare disease or condition.

Post-Approval Requirements

Any products manufactured or distributed pursuant to FDA approvals are subject to pervasive and continuing regulation by the FDA, including, among other things, requirements relating to record-keeping, reporting of adverse experiences and significant interruptions in manufacturing, periodic reporting, product sampling and distribution, and advertising and promotion of the product. After approval, most changes to the approved product, such as adding new indications or other labeling claims, are subject to prior FDA review and approval. There also are continuing user fee requirements, under which FDA assesses an annual program fee for each product identified in an approved BLA. Biologic manufacturers and their subcontractors are required to register their establishments with the FDA and certain state agencies, and are subject to periodic unannounced inspections by the FDA and certain state agencies for compliance with cGMP, which impose certain procedural and documentation requirements upon BLA sponsors and any third-party manufacturers. Changes to the manufacturing process are strictly regulated, and, depending on the significance of the change, may require prior FDA approval before being implemented. FDA regulations also require investigation and correction of any deviations from cGMP and impose reporting requirements upon us and any third-party manufacturers that we may decide to use. Accordingly, manufacturers must continue to expend time, money and effort in the area of production and quality control to maintain compliance with cGMP and other aspects of regulatory compliance.

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The FDA may withdraw approval if compliance with regulatory requirements and standards is not maintained or if problems occur after the product reaches the market. Later discovery of previously unknown problems with a product, including adverse events of unanticipated severity or frequency, or with manufacturing processes, or failure to comply with regulatory requirements, may result in revisions to the approved labeling to add new safety information; imposition of post-market studies or clinical studies to assess new safety risks; or imposition of distribution restrictions or other restrictions under a REMS program. Other potential consequences include, among other things:

The FDA closely regulates the marketing, labeling, advertising and promotion of biologics. A company can make only those claims relating to safety and efficacy, purity and potency that are for uses of the product approved by the FDA, that are considered consistent with the approved label, and for which the company has appropriate substantiation, as applicable. The FDA and other agencies actively enforce the laws and regulations prohibiting the promotion of off-label uses. Failure to comply with these requirements can result in, among other things, adverse publicity, warning letters, corrective advertising and potential civil and criminal penalties. Physicians may prescribe legally available products for uses that are not described in the product’s labeling and that differ from those tested by us and approved by the FDA. Such off-label uses are common across medical specialties. Physicians may believe that such off-label uses are the best treatment for many patients in varied circumstances. The FDA does not regulate the behavior of physicians in their choice of treatments. The FDA does, however, restrict manufacturer’s communications on the subject of off-label use of their products.

Biosimilars and Reference Product Exclusivity

The Patient Protection and Affordable Care Act, as amended by the Health Care and Education Reconciliation Act, or collectively, the ACA, signed into law in 2010, includes a subtitle called the Biologics Price Competition and Innovation Act of 2009, or BPCIA, which created an abbreviated approval pathway for biological products that are biosimilar to or interchangeable with an FDA-approved reference biological product. A number of biosimilars have been licensed under the BPCIA, and numerous biosimilars have been approved in Europe, but no interchangeable biologic has been approved in the United States. The FDA has issued several guidance documents outlining an approach to review and approval of biosimilars.

Biosimilarity, which requires that there be no clinically meaningful differences between the biological product and the reference product in terms of safety, purity, and potency, can be shown through analytical studies, animal studies, and a clinical study or studies. Interchangeability requires that a product is biosimilar to the reference product and the product must demonstrate that it can be expected to produce the same clinical results as the reference product in any given patient and, for products that are administered to a patient more than once, the biologic and the reference biologic may be alternated or switched after one has been previously administered without increasing safety risks or risks of diminished efficacy relative to exclusive use of the reference biologic. Complexities associated with the larger, and often more complex, structures of biological products, as well as the processes by which such products are manufactured, pose significant hurdles to implementation of the abbreviated approval pathway, particularly for interchangeability determinations, that are still being worked out by the FDA.

Under the BPCIA, an application for a biosimilar product may not be submitted to the FDA until four (4) years following the date that the reference product was first licensed by the FDA. In addition, the FDA may not approve a biosimilar product until twelve (12) years from the date on which the reference product was first licensed. During this 12-year period of exclusivity, another company may still market a competing version of the reference product if the FDA approves an original BLA containing that applicant’s own preclinical data and data from adequate and well-controlled clinical trials to demonstrate the safety, purity and potency of the competing product. The BPCIA also created certain exclusivity periods for biosimilars approved as interchangeable products. At this juncture, it is unclear whether products deemed “interchangeable” by the FDA will, in fact, be readily substituted by pharmacies, which are governed by state pharmacy law.

The BPCIA is complex and continues to be interpreted and implemented by the FDA. In addition, government proposals have sought to reduce the 12-year reference product exclusivity period. Other aspects of the BPCIA, some of which may impact the BPCIA

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exclusivity provisions, as well as the ACA as a whole, have been the subject of recent litigation. As a result, the ultimate implementation and impact of the BPCIA is subject to significant uncertainty.

On December 20, 2019, the Further Consolidated Appropriations Act, 2020, or FCAA 2020, became law. Section 610 of Division N Title I, entitled “Actions for Delays of Generic Drugs and Biosimilar Biological Products”, provides biosimilar developers with a private right of action to obtain sufficient quantities of reference product from the brand manufacturer or another biosimilar manufacturer, necessary for approval of the developers’ biosimilar product. If a biosimilar developer is successful in its suit, the defendant manufacturer would be required to provide sufficient quantities of product on commercially-reasonable, market-based terms and may be required to pay the developer’s reasonable attorney’s fees and costs as well as financial compensation under certain circumstances. The purpose of section 610 is to promote competition in the market for drugs and biological products by facilitating the timely entry of lower-cost biosimilar products. We cannot determine what effect this may have on manufacturers that may develop biosimilar or other competing versions of our products once approved.

Other Healthcare Laws and Compliance Requirements

Pharmaceutical companies are subject to additional healthcare regulation and enforcement by the federal government and by authorities in the states and foreign jurisdictions in which they conduct their business, which may constrain the financial arrangements and relationships through which we and our partners research, sell, market and distribute any products for which we obtain marketing approval. Such laws include, without limitation, state and federal anti-kickback, fraud and abuse, false claims, data privacy and security and transparency laws regarding drug pricing and payments and other transfer of value to physicians and other healthcare providers. If their operations are found to be in violation of any of such laws or any other governmental regulations that apply, they may be subject to penalties, including, without limitation, civil, criminal and administrative penalties, damages, fines, exclusion from government-funded healthcare programs, such as Medicare and Medicaid or similar programs in other countries or jurisdictions, integrity oversight and reporting obligations to resolve allegations of non-compliance, disgorgement, imprisonment, contractual damages, reputational harm, diminished profits and the curtailment or restructuring of our operations.

Data Privacy and Security Laws

Numerous state, federal and foreign laws, including consumer protection laws and regulations, govern the collection, dissemination, use, access to, confidentiality and security of personal information, including health-related information. In the United States, numerous federal and state laws and regulations, including data breach notification laws, health information privacy and security laws, including the Health Insurance Portability and Accountability Act of 1996, as amended, and regulations promulgated thereunder, collectively, or HIPAA, and federal and state consumer protection laws and regulations (e.g., Section 5 of the FTC Act), that govern the collection, use, disclosure, and protection of health-related and other personal information could apply to our operations or the operations of our partners. In addition, certain state and non-U.S. laws, such as the California Consumer Privacy Act, or CCPA, the California Privacy Rights Act, or CPRA, and the EU General Data Protection Regulation, or GDPR, govern the privacy and security of personal data, including health-related data in certain circumstances, some of which are more stringent than HIPAA and many of which differ from each other in significant ways and may not have the same effect, thus complicating compliance efforts. Failure to comply with these laws, where applicable, can result in the imposition of significant civil and/or criminal penalties and private litigation. Privacy and security laws, regulations, and other obligations are constantly evolving, may conflict with each other to complicate compliance efforts, and can result in investigations, proceedings, or actions that lead to significant civil and/or criminal penalties and restrictions on data processing.

Coverage and Reimbursement

Significant uncertainty exists as to the coverage and reimbursement status of any pharmaceutical or biological product for which we obtain regulatory approval. Sales of any product depend, in part, on the extent to which such product will be covered by third-party payors, such as federal, state, and foreign government healthcare programs, commercial insurance and managed healthcare organizations, and the level of reimbursement for such product by third-party payors. Decisions regarding the extent of coverage and amount of reimbursement to be provided are made on a plan-by-plan basis. For products administered under the supervision of a physician, obtaining coverage and adequate reimbursement may be particularly difficult because of the higher prices often associated with such drugs. Additionally, separate reimbursement for the product itself or the treatment or procedure in which the product is used may not be available, which may impact physician utilization.

In addition, the U.S. government, state legislatures and foreign governments have continued implementing cost-containment programs, including price controls, restrictions on coverage and reimbursement and requirements for substitution of generic products. Third-party payors are increasingly challenging the prices charged for medical products and services, examining the medical necessity

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and reviewing the cost effectiveness of pharmaceutical or biological products, medical devices and medical services, in addition to questioning safety and efficacy. Adoption of price controls and cost-containment measures, and adoption of more restrictive policies in jurisdictions with existing controls and measures, could further limit sales of any product. Decreases in third-party reimbursement for any product or a decision by a third-party payor not to cover a product could reduce physician usage and patient demand for the product. No regulatory authority has granted approval for a personalized cancer immunotherapy based on a vaccine approach, and there is no model for reimbursement of this type of product.

Healthcare Reform

The United States and some foreign jurisdictions are considering or have enacted a number of reform proposals to change the healthcare system. There is significant interest in promoting changes in healthcare systems with the stated goals of containing healthcare costs, improving quality or expanding access. In the United States, the pharmaceutical industry has been a particular focus of these efforts and has been significantly affected by federal and state legislative initiatives, including those designed to limit the pricing, coverage, and reimbursement of pharmaceutical and biopharmaceutical products, especially under government-funded health care programs, and increased governmental control of drug pricing.

In March 2010, the ACA was signed into law, which substantially changed the way healthcare is financed by both governmental and private insurers in the United States, and significantly affected the pharmaceutical industry. The ACA contains a number of provisions of particular import to the pharmaceutical and biotechnology industries, including, but not limited to, those governing enrollment in federal healthcare programs, a new methodology by which rebates owed by manufacturers under the Medicaid Drug Rebate Program are calculated for drugs that are inhaled, infused, instilled, implanted or injected, and annual fees based on pharmaceutical companies’ share of sales to federal health care programs. Since its enactment, there have been judicial, Congressional, and executive branch challenges to certain aspects of the ACA. For example, the Tax Act was enacted, which, among other things, removes penalties for not complying with ACA’s individual mandate to carry health insurance. On December 14, 2018, a U.S. District Court Judge in the Northern District of Texas, ruled that the individual mandate is a critical and inseverable feature of the ACA, and therefore, because it was repealed as part of the Tax Act, the remaining provisions of the ACA are invalid as well. On December 18, 2019, the U.S. Court of Appeals for the 5th Circuit upheld the District Court's decision that the individual mandate was unconstitutional but remanded the case back to the District Court to determine whether the remaining provisions of the ACA are invalid as well. In January 2020, petitions for certiorari were filed requesting that the U.S. Supreme Court review the Fifth Circuit’s decision and ultimately decide the constitutionality of the ACA. In March 2020, the U.S. Supreme Court granted certiorari in the consolidated cases of Texas v. California and California v. Texas, both of which address the Fifth Circuit’s decision to strike down the individual mandate, while sending back to the district court the question of the overall law’s constitutionality. The U.S. Supreme Court heard oral arguments in this case in November 2020. It is also unclear how other efforts, if any, to challenge, repeal or replace the ACA will impact the ACA.

Other legislative changes have been proposed and adopted since the ACA was enacted, including aggregate reductions of Medicare payments to providers of 2% per fiscal year, which was temporarily suspended from May 1, 2020 through March 31, 2021, and reduced payments to several types of Medicare providers.

Moreover, there has been heightened governmental scrutiny over the manner in which manufacturers set prices for their marketed products, which has resulted in several Congressional inquiries, hearings and proposed and enacted federal legislation and rules, as well as Executive Orders, designed to, among other things, reduce or limit the prices of drugs and make them more affordable for patients, such as by tying the prices that Medicare reimburses for physician-administered drugs to the prices of drugs in other countries, reform the structure and financing of Medicare Part D pharmaceutical benefits, including through increasing manufacturer contributions to offset Medicare beneficiary costs, bring more transparency to drug pricing rationale and methodologies, enable the government to negotiate prices for drugs covered under Medicare, including H.R. 3 which passed the House, revise rules associated with the calculation of Medicaid Average Manufacturer Price and Best Price, including potentially removing the current statutory 100% of Average Manufacturer Price per-unit cap on Medicaid rebate liability, which may significantly affect the amount of rebates paid on prescription drugs under Medicaid, eliminate anti-kickback statute discount safe harbor protection for manufacturer rebate arrangements with Medicare Part D Plan Sponsors and pharmacy benefit managers on behalf of Part D Plan Sponsors, which is currently stayed, create new anti-kickback statute safe harbors applicable to certain point-of-sale discounts to patients and fixed-fee administrative fee payment arrangements with pharmacy benefit managers, and facilitate the importation of certain lower-cost drugs from other countries. At the state level, legislatures have increasingly passed legislation and implemented regulations designed to control pharmaceutical product pricing, including price or patient reimbursement constraints, discounts, restrictions on certain product access and marketing cost disclosure and transparency measures, and, in some cases, designed to encourage importation from other countries and bulk purchasing.

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Additionally, on May 30, 2018, the Trickett Wendler, Frank Mongiello, Jordan McLinn, and Matthew Bellina Right to Try Act of 2017, or the Right to Try Act, was signed into law. The law, among other things, provides a federal framework for certain patients to access certain investigational new drug products that have completed a Phase I clinical trial and that are undergoing investigation for FDA approval. Under certain circumstances, eligible patients can seek treatment without enrolling in clinical trials and without obtaining FDA permission under the FDA expanded access program. There is no obligation for a pharmaceutical manufacturer to make its drug products available to eligible patients as a result of the Right to Try Act.

Our Interactions with the FDA

EDGE Medical Device Development

In two separate FDA interactions, the FDA advised us that our machine learning software will not be subject to medical device diagnostic regulations. In August 2016, the FDA’s Center for Devices and Radiological Health (“CDRH”), determined that the TSNA prediction software is a Non-Significant Risk, or NSR, device, and that an investigational device exemption (“IDE”), submission is not required to conduct clinical studies with our product candidate. In April 2017, the FDA’s Center for Biologics Evaluation and Research, or CBER, confirmed that medical device diagnostic regulations do not apply to our testing and processing of the patient-specific TSNA, and that quality requirements could be met through compliance with biologic cGMPs. Based on these interactions, we believe no additional device-related regulatory submissions (such as an IDE or pre-market approval application (“PMA”)) or device development activities are required and our TSNA prediction software procedure will be regulated as part of our cGMP manufacturing process.

GRANITE Development Program

Preclinical Safety

To address the personalized nature of our therapy in a Pre-Pre-IND interaction with the FDA’s CBER Office of Tissues and Advanced Therapies, or OTAT, the FDA advised us that a single toxicological animal study with a representative vector could be able to support preclinical safety for purposes of IND submission. Subsequent to this discussion, we submitted proposed protocols for GLP toxicology and biodistribution studies for OTAT’s review in connection with a Pre-IND meeting, and OTAT agreed that a single GLP toxicology study could support IND submission. In this GLP toxicology study, we administered our ChAdV and the SAM vectors to Indian Rhesus macaques. The heterologous prime-boost immunotherapy approach when administered intramuscularly was well tolerated at the clinical maximal dose of each platform, with some animals presenting flu-like symptoms. Preclinical chemistry findings included a transient increase in select cytokines, which resolved rapidly.

Clinical Regulatory

In our GRANITE Pre-IND meeting with OTAT, the FDA previewed Clinical Protocol GO-004 and confirmed that the overall design appeared reasonable, while providing comments on the study populations and dose determination which we incorporated into the Phase1/2 protocol. OTAT also concurred with our dose limiting toxicity assessment criteria, but reserved comment on the starting dose and dose escalation pending the completion of planned preclinical studies. We intend to include these elements in the protocol, which may permit a faster progression and fewer patients to reach the clinical protocol’s combination cohort (Phase 1, Part C).

Regulatory Chemistry, Manufacturing & Controls

In a Type-C Facilities meeting with the FDA’s CBER Division of Manufacturing and Product Quality, or DMPQ, we obtained FDA feedback on our proposed design for the multi-use clinical manufacturing facility in Pleasanton, California. Importantly, the FDA concurred with our plan to build a facility designed to accommodate manufacture of multiple patient-specific lots in parallel within the same manufacturing suite, which we expect will provide a substantial increase in scalability within a smaller allocation of cleanrooms.

At our subsequent GRANITE Pre-IND meeting with OTAT, the FDA concurred with our proposed use of select rapid release testing methods in which we proposed replacing standard cell-culture based tests with faster polymerase chain reaction methods. As discussed with the FDA, we submitted qualification of these methods in our IND submission for GRANITE. The FDA also found our proposed stability program to be generally acceptable to support the proposed Phase 1 clinical study of GRANITE, where only one representative patient lot per year will be placed on product stability during conduct of the clinical program.

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In support of transitioning the GRANITE manufacturing process from external contract manufacturing organizations to Gritstone’s Pleasanton manufacturing facility, an IND amendment has been submitted to the FDA outlining the Chemistry, Manufacturing, and Controls documentation changes for the ChAdV and SAM products. These revisions include a plasmid backbone change for the SAM vector and a process improvement for the SAM drug substance. These updates have been implemented and are currently being utilized in Gritstone’s Pleasanton manufacturing facility.

GRANITE Regulatory Milestones

The FDA cleared our IND for GRANITE in September 2018. In December 2018, the FDA granted fast track designation to GRANITE for the treatment of colorectal cancer.

SLATE Development Program

Preclinical Safety

In pre-IND communications with the FDA, following a justification of comparability of ChAdV and SAM products, Gritstone received feedback that pre-clinical pharmacology, pharmacokinetic, and toxicology studies conducted in support of the GRANITE IND, could be used to support the safety of the clinical study proposed under the SLATE IND. In follow-up, the Agency requested additional safety pharmacology information on the general anticipated immunogenicity and auto-reactivity elicited with each of the 20 neoantigens expressed in the SLATE cassette, as well as the impact of order and orientation of the neoantigens within the expression cassette.

Clinical Regulatory

In our SLATE Pre-IND communication with OTAT, the FDA previewed Clinical Protocol GO-005 and confirmed that the overall design appeared reasonable and requested we add language to clarify our proposed dose escalation and stopping rules. The FDA had additional questions on our proposed Next Generation Sequencing method to screen patients for their HLA type and communicated that this novel method may be viewed as a companion diagnostic.

Regulatory Chemistry, Manufacturing & Controls

In review of the SLATE IND, much of the manufacturing process is similar to that used in the GRANITE IND, therefore, the Agency feedback focused primarily on the quality of the reagents, drug product characterization and release, and ongoing stability requests. The FDA inquired on the status of certain research-grade reagents and reminded Gritstone of the need to progress to GMP grade materials in the manufacture drug product by the time of BLA approval and commercial licensure. In order to retain consistency in the manufactured drug product across SLATE batches, we were asked to amend the specification of certain release assays’ criteria and continue the development of quantitative potency assays for the ChAdV and SAM products prior to approval, and we were asked to summarize our QC plan to prevent, detect, and correct deficiencies that may compromise product integrity or function, or that may lead to the possible transmission of adventitious infectious agents. Additionally, the Agency provided guidance on the proposed method for qualifying Gritstone’s proposed accelerated adventitious agent release assay.

SLATE Regulatory Milestones

The FDA cleared our IND for SLATE in June 2019.

CORAL Development Program

A pre-IND interaction with the FDA was conducted to review the proposed clinical investigation of ChAdV vectors encoding the SARS-CoV-2 and CD8+ T-cell epitope spike antigen sequences in normal healthy subjects. The FDA concluded that the overall manufacturing and release testing for the CORAL vaccines, which is similar to the GRANITE/SLATE process, appeared acceptable and requested detail on the transfection process, grade of materials, and release tests be submitted in the IND. Gritstone also received feedback that pre-clinical pharmacokinetic, and toxicology studies conducted in support of the GRANITE IND could be used to support the safety information needed to initiate the SARS-CoV-2 clinical study, and that additional animal immune response pharmacodynamic data would be submitted within the IND. The FDA previewed the proposed clinical protocol, confirmed that the overall design appeared reasonable and requested Gritstone include language to clarify dose escalation, stopping rules and a sentinel

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arm. The FDA requested that Gritstone exclude those subjects who are being treated with COVID-19 investigational agents or who have a high risk of potential exposure to SARS-CoV-2.

We expect an IND/DMF for this program will be filed with the FDA in March 2021.

Financial Information About Segments

We manage our operations as a single reportable segment for the purposes of assessing performance and making operating decisions. See "Note 2. Summary of Significant Accounting Policies" in the notes to the consolidated financial statements included elsewhere in this Annual Report on Form 10-K.

Employees

As a mission-driven organization, we value and foster a culture of collaboration, discovery and passion, which is reflected in our hiring and retention strategies. We employ talented individuals who have the skills and expertise to meet the challenges of our mission, and we recognize that our employees are key to our success. Our human capital resources objectives include hiring goals set to provide us with necessary expertise, integrating new employees, and retaining, incentivizing and developing our existing employees.

As of December 31, 2020, we had 169 full-time employees, including a total of 39 employees with M.D. or Ph.D. degrees. Within our workforce, 71 employees are engaged in research and development, 60 in manufacturing and quality, and 38 are engaged in business development, finance, legal, human resources, facilities, information technology and general management and administration. None of our employees are represented by labor unions or covered by collective bargaining agreements. We consider our relationship with our employees to be good.

Corporate Information

We were founded in August 2015 as a Delaware corporation. Our principal executive offices are located at 5959 Horton Street, Suite 300, Emeryville, California 94608, and our telephone number is (510) 871-6100. Our website address is www.gritstoneoncology.com. The information on, or that can be accessed through, our website is not part of this report and is not incorporated by reference herein. We have included our website address as an inactive textual reference only. We also use our website as a means of disclosing material non-public information and for complying with our disclosure obligations under Regulation FD.

We file electronically with the SEC our annual reports on Form 10-K, quarterly reports on Form 10-Q and current reports on Form 8-K pursuant to Section 13(a) or 15(d) of the Exchange Act. We make available on our website at www.gritstoneoncology.com, free of charge, copies of these reports, as soon as reasonably practicable after we electronically file such material with, or furnish it to, the SEC. The public may read or copy any materials we file with the SEC at the SEC's Public Reference Room at 100 F Street NE, Washington, D.C. 20549. The public may obtain information on the operation of the Public Reference Room by calling the SEC at 1-800-SEC-0330. The SEC maintains a website that contains reports, proxy and information statements, and other information regarding issuers that file electronically with the SEC. The address of that website is www.sec.gov. The information in or accessible through the SEC and our website or social media sites does not constitute part of this Annual Report on Form 10-K or any other report or document we file with the SEC, and any references to our website and social media sites are intended to be inactive textual references only.

We use Gritstone Oncology, Inc.®, the Gritstone Oncology logo, and other marks as trademarks in the United States and other countries. This Annual Report on Form 10-K contains references to our trademarks and service marks and to those belonging to other entities. Solely for convenience, trademarks and trade names referred to in this Annual Report on Form 10-K, including logos, artwork and other visual displays, may appear without the ® or ™ symbols, but such references are not intended to indicate in any way that we will not assert, to the fullest extent under applicable law, our rights or the rights of the applicable licensor to these trademarks and trade names. We do not intend our use or display of other entities’ trade names, trademarks or service marks to imply a relationship with, or endorsement or sponsorship of us by any other entity.

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Item 1A. Risk Factors.

Investing in our common stock involves a high degree of risk. You should carefully consider the risks described below, as well as the other information in this Annual Report, including our financial statements and the related notes and “Management’s Discussion and Analysis of Financial Condition and Results of Operations,” before deciding whether to invest in our common stock. The occurrence of any of the events or developments described below could have a material adverse effect on our business, results of operations, financial condition, prospects and stock price. In such an event, the market price of our common stock could decline, and you may lose all or part of your investment. Many of the following risks and uncertainties are, and will be, exacerbated by the COVID-19 pandemic and any worsening of the global business and economic environment as a result. Additional risks and uncertainties not presently known to us or that we currently deem immaterial may also impair our business operations.

Summary of Principal Risks Associated with Our Business

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Risks Related to Our Limited Operating History, Financial Condition and Capital Requirements

We are an early-stage biopharmaceutical company with a limited operating history and no products approved for commercial sale. We have incurred significant losses since our inception, and we anticipate that we will continue to incur significant losses for the foreseeable future, which, together with our limited operating history, makes it difficult to assess our future viability.

Biopharmaceutical product development is a highly speculative undertaking and involves a substantial degree of risk. We are an early-stage biopharmaceutical company, and we have only a limited operating history upon which you can evaluate our business and prospects. We have no products approved for commercial sale, have not generated any revenue from product sales and have incurred losses in each year since our inception in August 2015. In addition, we have limited experience and have not yet demonstrated an ability to successfully overcome many of the risks and uncertainties frequently encountered by companies in new and rapidly evolving fields, particularly in the biopharmaceutical industry. We initiated our Phase 1/2 clinical trials, GO-004 for our first personalized cancer immunotherapy candidate, GRANITE, in the fourth quarter of 2018 and GO-005 for our off-the-shelf cancer immunotherapy candidate, SLATE, in the third quarter of 2019. We are collaborating on a Phase 1 clinical trial of our second-generation vaccine candidate against SARS-CoV-2, CORAL, to be conducted through the NIAID-supported IDCRC, for which the IND has been approved and volunteer subjects enrollment will start imminently.

We have had significant operating losses since our inception. Our net losses for the years ended December 31, 2020, 2019 and 2018 were approximately $105.3 million, $94.4 million and $64.8 million, respectively. As of December 31, 2020, we had an accumulated deficit of $326.3 million. Substantially all of our losses have resulted from expenses incurred in connection with our research and development programs and from general and administrative costs associated with our operations. Our GRANITE, SLATE, and BiSAb programs will require substantial additional development time and resources before we would be able to apply for or receive regulatory approvals and begin generating revenue from product sales. In addition, we expect to incur additional costs associated with operating as a public company. We also do not yet have a sales organization or commercial infrastructure and, accordingly, if our product candidates are approved, we will incur significant expenses to develop a sales organization or commercial infrastructure in advance of generating any commercial product sales. We expect to continue to incur losses for the foreseeable future, and we anticipate these losses will increase as we continue to develop GRANITE, SLATE, the BiSAb program and any future product candidates, conduct clinical trials and pursue research and development activities. Even if we achieve profitability in the future, we may not be able to sustain profitability in subsequent periods. Our prior losses, combined with expected future losses, have had and will continue to have an adverse effect on our stockholders’ equity and working capital.

We will require substantial additional financing to achieve our goals, and a failure to obtain this necessary capital when needed on acceptable terms, or at all, could force us to delay, limit, reduce or terminate our product development programs, commercialization efforts or other operations.

Since our inception, we have invested a significant portion of our efforts and financial resources in research and development activities for tumor-specific cancer immunotherapies and working to establish our in-house manufacturing capabilities. Preclinical studies and clinical trials and additional research and development activities will require substantial funds to complete. As of December 31, 2020, we had capital resources consisting of cash, cash equivalents and marketable securities of $171.1 million. We believe that we will continue to expend substantial resources for the foreseeable future in connection with the development of GRANITE, SLATE, our BiSAb program, and any other future cancer immunotherapy candidates we may choose to pursue, as well as the continued development of our manufacturing capabilities and other corporate uses. Specifically, in the near term, we expect to incur substantial expenses as we advance GRANITE and SLATE through clinical development, seek regulatory approval, prepare for and, if approved, proceed to commercialization, continue our research and development efforts and invest in our manufacturing facility. These expenditures will include costs associated with conducting preclinical studies and clinical trials, obtaining regulatory approvals, and manufacturing and supply, as well as marketing and selling any products approved for sale. In addition, other unanticipated costs may arise. Because the outcome of any preclinical study or clinical trial is highly uncertain, we cannot reasonably estimate the actual amounts necessary to successfully complete the development and commercialization of GRANITE, SLATE or any future immunotherapy product candidates.

We believe that our existing cash, cash equivalents and marketable securities will be sufficient to fund our planned operations for at least twelve (12) months. However, our operating plans and other demands on our capital resources may change as a result of many factors currently unknown to us, and we may need to seek additional funds sooner than planned, through public or private equity or debt financings or other sources, such as strategic collaborations. Such financing may result in dilution to stockholders, imposition

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of burdensome debt covenants and repayment obligations, or other restrictions that may affect our business. If we raise additional funds through licensing or collaboration arrangements with third parties, we may have to relinquish valuable rights to our product candidates or grant licenses on terms that are not favorable to us. In addition, we may seek additional capital due to favorable market conditions or strategic considerations even if we believe we have sufficient funds for our current or future operating plans. Attempting to secure additional financing may divert our management from our day-to-day activities, which may adversely affect our ability to develop our product candidates. In addition, we cannot guarantee that future financing will be available in sufficient amounts or on terms acceptable to us, if at all.

Our future capital requirements depend on many factors, including:

Additional funds may not be available when we need them, on terms that are acceptable to us, or at all. If adequate funds are not available to us on a timely basis, we may be required to:

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We also could be required to seek funds through arrangements with collaborators or others that may require us to relinquish rights or jointly own some aspects of our technologies or product candidates that we would otherwise pursue on our own. We do not expect to realize revenue from sales of products or royalties from licensed products in the foreseeable future, if at all, and unless and until a product candidate is clinically tested, approved for commercialization and successfully marketed. To date, we have primarily financed our operations through the sale of equity securities. We will be required to seek additional funding in the future and currently intend to do so through collaborations, public or private equity offerings or debt financings, credit or loan facilities or a combination of one or more of these funding sources. Our ability to raise additional funds will depend on financial, economic and other factors, many of which are beyond our control. Additional funds may not be available to us on acceptable terms or at all. If we raise additional funds by issuing equity securities, our stockholders will suffer dilution and the terms of any financing may adversely affect the rights of our stockholders. In addition, as a condition to providing additional funds to us, future investors may demand, and may be granted, rights superior to those of existing stockholders. Debt financing, if available, is likely to involve restrictive covenants limiting our flexibility in conducting future business activities, and, in the event of insolvency, debt holders would be repaid before holders of our equity securities received any distribution of our corporate assets.

Our operating results may fluctuate significantly, which makes our future operating results difficult to predict and could cause our operating results to fall below expectations.

Our quarterly and annual operating results may fluctuate significantly, which makes it difficult for us to predict our future operating results. These fluctuations may occur due to a variety of factors, many of which are outside of our control and may be difficult to predict, including:

The cumulative effects of these factors could result in large fluctuations and unpredictability in our quarterly and annual operating results. As a result, comparing our operating results on a period-to-period basis may not be meaningful. Investors should not rely on our past results as an indication of our future performance.

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This variability and unpredictability could also result in our failing to meet the expectations of industry or financial analysts or investors for any period. If our revenue or operating results fall below the expectations of analysts or investors or below any forecasts we may provide to the market, or if the forecasts we provide to the market are below the expectations of analysts or investors, the price of our common stock could decline substantially. Such a stock price decline could occur even when we have met any previously publicly stated revenue or earnings guidance we may provide.

Risks Related to Our Business

Our business is highly dependent on the successful development, regulatory approval and commercialization of our product candidates, primarily our personalized immunotherapy product candidate, GRANITE, and our “off-the-shelf” immunotherapy product candidate, SLATE, both of which are in early-stage clinical trials.

We have no products approved for sale. Both GRANITE and SLATE are in the early stages of clinical trials. As such, we face significant translational risk with GRANITE and SLATE specifically and our tumor-specific immunotherapy approach generally. The success of our business, including our ability to finance our company and generate any revenue in the future, will primarily depend on the successful development, regulatory approval and commercialization of GRANITE and SLATE, as well as other product candidates derived from our tumor-specific immunotherapy approach, which may never occur. In the future, we may also become dependent on other product candidates that we may develop or acquire; however, our product candidates based on our tumor-specific immunotherapy approach have only been tested in a small number of humans, and, given our early stage of development, it may be many years, if at all, before we have demonstrated the safety and efficacy of a personalized immunotherapy treatment sufficient to warrant approval for commercialization.

We have not previously submitted a biologics license application, or BLA, to the FDA, or similar filing seeking regulatory approval to comparable foreign authorities, for any product candidate, and we cannot be certain that our product candidates will be successful in clinical trials or receive regulatory approval. Further, GRANITE, SLATE or any future product candidates (including CORAL and our HIV vaccine) may not receive regulatory approval even if they are successful in clinical trials. If we do not receive regulatory approvals for our product candidates, we may not be able to continue our operations. Even if we successfully obtain regulatory approvals to market a product candidate, our revenue will be dependent, in part, upon the size of the markets in the territories for which we gain regulatory approval and have commercial rights. If the markets or patient subsets that we are targeting are not as significant as we estimate, we may not generate significant revenues from sales of such products, if approved.

We plan to seek regulatory approval to commercialize our product candidates both in the United States and in selected foreign countries. While the scope of regulatory approval generally is similar in other countries, in order to obtain separate regulatory approval in other countries we must comply with numerous and varying regulatory requirements of such countries regarding safety and efficacy. Other countries also have their own regulations governing, among other things, clinical trials and commercial sales, as well as pricing and distribution of our product candidates, and we may be required to expend significant resources to obtain regulatory approval and to comply with ongoing regulations in these jurisdictions.

The clinical and commercial success of our current and any future product candidates will depend on a number of factors, including the following:

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These factors, many of which are beyond our control, could cause us to experience significant delays or an inability to obtain regulatory approvals or commercialize our current or future product candidates. Even if regulatory approvals are obtained, we may never be able to successfully commercialize any product candidates. Accordingly, we cannot provide assurances that we will be able to generate sufficient revenue through the sale of our product candidate or any future product candidates to continue our business or achieve profitability.

Our tumor-specific cancer immunotherapy approach is based on novel ideas and technologies that are unproven and may not result in marketable products, which exposes us to unforeseen risks and makes it difficult for us to predict the time and cost of product development and potential for regulatory approval.

We are using our proprietary EDGE tumor-antigen prediction platform to develop tumor-specific immunotherapy product candidates to treat cancer. Our foundational science and product development approach are based on our ability to predict the presence of a patient’s tumor-specific neoantigens, or TSNA, and develop a TSNA-directed therapy that will elicit a meaningful T cell response. We believe that this approach may offer an improved therapeutic effect by driving an intense, focused T cell attack selectively upon a patient’s tumor. However, this approach to treating cancer is novel and the scientific research that forms the basis of our efforts to predict the presence of TSNA and to develop TSNA-directed cancer immunotherapy candidates is both preliminary and limited. The results of our preclinical animal studies may not translate into humans. For example, our prediction model may fail to accurately predict the presence of TSNA, resulting in little or no T cell activity, or our therapy may fail to elicit a significant or durable enough T cell response to effectively destroy a tumor. As such, we cannot assure you that even if we are able to develop

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personalized cancer immunotherapy candidates capable of recognizing TSNA and eliciting a T cell response, that such therapy would safely and effectively treat cancers. We may spend substantial funds attempting to develop this approach and never succeed in developing a marketable therapeutic.

No regulatory authority has granted approval for a cancer immunotherapy based on a heterologous prime-boost approach, which may increase the complexity, uncertainty and length of the regulatory approval process for our product candidates. We may never receive approval to market and commercialize any product candidate. Even if we obtain regulatory approval, the approval may be for targets, disease indications, lines of therapy or patient populations that are not as broad as we intended or desired or may require labeling that includes significant use or distribution restrictions or safety warnings. We may be required to perform additional or unanticipated clinical trials to obtain approval or be subject to post-marketing testing requirements to maintain regulatory approval. If our personalized immunotherapy candidates prove to be ineffective, unsafe or commercially unviable, our entire technology platform and pipeline would have little, if any, value, which would have a material and adverse effect on our business, financial condition, results of operations and prospects.

The regulatory approval process and clinical trial requirements for novel product candidates can be more expensive and take longer than for other, better known or more extensively studied product candidates, and we cannot predict how long it will take or how much it will cost to complete clinical developments and obtain regulatory approvals for a cell therapy product candidate in the United States or how long it will take to commercialize a product candidate, if and when approved. Regulatory requirements governing cell therapy products have changed frequently and may continue to change in the future. For example, the FDA established the Office of Tissues and Advanced Therapies within its Center for Biologics Evaluation and Research, or CBER, to consolidate the review of cell therapies and related products, and the Cellular, Tissue and Gene Therapies Advisory Committee to advise CBER on its review. These and other regulatory review agencies, committees and advisory groups and the requirements and guidelines they promulgate may lengthen the regulatory review process, require us to perform additional preclinical studies or clinical trials, increase our development costs, lead to changes in regulatory positions and interpretations, delay or prevent approval and commercialization of these treatment candidates or lead to significant post-approval limitations or restrictions. Additionally, under the National Institutes of Health, or NIH, Guidelines for Research Involving Recombinant DNA Molecules, or the NIH Guidelines, supervision of human gene transfer trials includes evaluation and assessment by an institutional biosafety committee, or IBC, a local institutional committee that reviews and oversees research utilizing recombinant or synthetic nucleic acid molecules at that institution. The IBC assesses the safety of the research and identifies any potential risk to public health or the environment, and such review may result in some delay before initiation of a clinical trial. While the NIH Guidelines are not mandatory unless the research in question is being conducted at or sponsored by institutions receiving NIH funding of recombinant or synthetic nucleic acid molecule research, many companies and other institutions not otherwise subject to the NIH Guidelines voluntarily follow them.

Even if our product candidates obtain required regulatory approvals, such approvals may later be withdrawn as a result of changes in regulations or the interpretation of regulations by applicable regulatory agencies. Additionally, adverse developments in clinical trials conducted by others of cell therapy products or products created using similar technology, or adverse public perception of the field of cell therapies editing, may cause the FDA and other regulatory bodies to revise the requirements for approval of any product candidates we may develop or limit the use of products utilizing technologies such as ours, either of which could materially harm our business. As we advance our product candidates, we will be required to consult with various regulatory authorities, and we must comply with applicable laws, rules, and regulations, which may change from time to time including during the course of development of our product candidates. If we fail to do so, we may be required to delay or discontinue the clinical development of certain of our product candidates. These additional processes may result in a review and approval process that is longer than we otherwise would have expected. Even if we comply with applicable laws, rules, and regulations, and even if we maintain close coordination with the applicable regulatory authorities with oversight over our product candidates, our development programs may fail to succeed. Delay or failure to obtain, or unexpected costs in obtaining, the regulatory approval necessary to bring a potential product to market would materially and adversely affect our business, financial condition, results of operations and prospects.

Results of earlier studies and trials of our product candidates may not be predictive of future trial results.

Clinical testing is expensive and can take many years to complete, and its outcome is inherently uncertain. Failure or delay can occur at any time during the clinical trial process. Success in preclinical studies and early clinical trials does not ensure that later clinical trials will be successful. A number of companies in the biotechnology and pharmaceutical industries have suffered significant setbacks in clinical trials, even after positive results in earlier preclinical studies or clinical trials. These setbacks have been caused by, among other things, preclinical findings made while clinical trials were underway and safety or efficacy observations made in clinical trials, including previously unreported adverse events. Notwithstanding any potential promising results in earlier studies and trials, we cannot be certain that we will not face similar setbacks. Even if our clinical trials are completed, the results may not be sufficient to obtain regulatory approval for our product candidates. In addition, the results of our preclinical animal studies, including our non-human primate studies, may not be predictive of the results of outcomes in human clinical trials. For example, our tumor-specific cancer immunotherapy candidates and any future product candidates may demonstrate different chemical, biological and

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pharmacological properties in patients than they do in laboratory studies or may interact with human biological systems in unforeseen or harmful ways. Product candidates in later stages of clinical trials may fail to show the desired pharmacological properties or safety and efficacy traits despite having progressed through preclinical studies and initial clinical trials. Even if we are able to initiate and complete clinical trials, the results may not be sufficient to obtain regulatory approval for our product candidates.

Clinical development involves a lengthy and expensive process with an uncertain outcome, and delays can occur for a variety of reasons outside of our control.

Clinical development is expensive and can take many years to complete, and its outcome is inherently uncertain. Failure can occur at any time during the clinical trial process. Although we initiated our Phase 1/2 clinical trials, GO-004 in the fourth quarter of 2018 and GO-005 in the third quarter of 2019, we may experience delays in enrolling or completing those trials. Additionally, we cannot be certain that studies or trials for GRANITE, SLATE or any future product candidates will begin on time, not require redesign, enroll an adequate number of subjects on time or be completed on schedule, if at all. Clinical trials can be delayed or terminated for a variety of reasons, including delays or failures related to:

In addition, disruptions caused by the COVID-19 pandemic may increase the likelihood that we encounter such difficulties or delays in initiating, enrolling, conducting or completing our planned and ongoing clinical trials. We are also aware that several CROs based in the U.S. that provide preclinical services are experiencing heavy demand which may impact their ability to start new studies and lead to delays in the commencement of our preclinical studies. In addition, several U.S.-based academic research organizations have also experienced shutdowns. However, neither of these has caused any material impact on our business.

We may experience numerous adverse or unforeseen events during, or as a result of, preclinical studies and clinical trials that could delay or prevent our ability to receive marketing approval or commercialize our product candidates, including:

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If we are required to conduct additional clinical trials or other testing of our product candidates beyond those that we currently contemplate, if we are unable to successfully complete clinical trials of our product candidates or other testing, if the results of these trials or tests are not positive or are only moderately positive or if there are safety concerns, we may:

We could also encounter delays if a clinical trial is suspended or terminated by us, by the IRBs of the institutions in which such trials are being conducted, by the Data Safety Monitoring Board, or DSMB, for such trial or by the FDA or other regulatory authorities. Such authorities may suspend or terminate a clinical trial due to a number of factors, including failure to conduct the clinical trial in accordance with regulatory requirements or our clinical protocols, inspection of the clinical trial operations or trial site by the FDA or other regulatory authorities resulting in the imposition of a clinical hold, unforeseen safety issues or adverse side effects, failure to demonstrate a benefit from using a product candidate, changes in governmental regulations or administrative actions or lack of adequate funding to continue the clinical trial.

Further, conducting clinical trials in foreign countries, as we may do for certain of our product candidates, presents additional risks that may delay completion of our clinical trials. These risks include the failure of enrolled patients in foreign countries to adhere to clinical protocol as a result of differences in healthcare services or cultural customs, managing additional administrative burdens associated with foreign regulatory schemes, as well as political and economic risks relevant to such foreign countries.

Principal investigators for our clinical trials may serve as scientific advisors or consultants to us from time to time and may receive cash or equity compensation in connection with such services. If these relationships and any related compensation result in perceived or actual conflicts of interest, or a regulatory authority concludes that the financial relationship may have affected the interpretation of the trial, the integrity of the data generated at the applicable clinical trial site may be questioned and the utility of the

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clinical trial itself may be jeopardized, which could result in the delay or rejection of the marketing application we submit. Any such delay or rejection could prevent or delay us from commercializing our current or future product candidates.

If any of our preclinical studies or clinical trials of our product candidates are delayed or terminated, the commercial prospects of our product candidates may be harmed, and our ability to generate revenues from any of these product candidates will be delayed or not realized at all. In addition, any delays in completing our clinical trials may increase our costs, slow down our product candidate development and approval process and jeopardize our ability to commence product sales and generate revenues. Any of these occurrences may significantly harm our business, financial condition and prospects. In addition, many of the factors that cause, or lead to, a delay in the commencement or completion of clinical trials may also ultimately lead to the denial of regulatory approval of our product candidates. If GRANITE, SLATE, any future product candidates or our TSNA prediction platform generally prove to be ineffective, unsafe or commercially unviable, our entire platform and approach would have little, if any, value, which would have a material and adverse effect on our business, financial condition, results of operations and prospects.

As a result of our trial design for GO-004 and GO-005, the Phase 1 portion of the trials will provide little evidence of the efficacy of our personalized immunotherapy product candidate, GRANITE and the off-the-shelf immunotherapy candidate, SLATE, respectively.

Scientific principles and preclinical data suggest that combination treatment of cancer patients with our TSNA-directed immunotherapy product candidates plus checkpoint inhibitors is likely to be most effective for our target indications. The Phase 1 portion of both of our Phase 1/2 clinical trials, GO-004 and GO-005, will, consequently, involve administration of a combination therapy with GRANITE and SLATE, respectively. Notably, all patients in the Phase 1 portion of these trials will receive anti-PD-1 monoclonal antibodies, or mAb, as background therapy. Some patients in both trials will additionally receive anti-CTLA-4 mAb. Checkpoint inhibitors such as anti-PD-1 and anti-CTLA-4 mAb are known to be effective treatments in many cancer patients and elicit objective responses in some patients. Any objective responses observed in our Phase 1 trials will thus be in patients receiving our experimental therapy together with a checkpoint inhibitor and attribution of objective responses to the effects of GRANITE or SLATE alone will not be possible. We expect that efficacy will be studied carefully in the respective programs’ Phase 2 cohorts, in which the relative contributions of our personalized and off-the-shelf immunotherapy candidates and the checkpoint inhibitors will be dissected and quantified to some degree. Of note, patient eligibility for our clinical trials is determined based, in part, upon predicted immunogenicity of the patient’s tumor. In particular, we only accept patients predicted to have a neoantigenic burden above a certain threshold. Selection of high-immunogenicity tumors is relevant to interpretation of clinical data, since high immunogenicity (which is related to high tumor mutational burden) may be a positive prognostic factor that means our selected patients would have a clinical outcome upon standard therapy which is superior to unselected case controls. As a result, interpretation of “time-to-event” endpoints such as progression-free survival or overall survival will be challenging without a contemporaneous, randomized control group. As a result, the Phase 1 portions of our respective Phase 1/2 clinical trials will provide little evidence of the efficacy of GRANITE or SLATE, which may not be fully understood by investors or market participants, potentially leading to negative effects on our stock price.

We may be unable to obtain regulatory approval for our tumor-specific immunotherapy product candidates under applicable regulatory requirements. The denial or delay of any such approval would delay or prevent commercialization of our product candidates and adversely impact our potential to generate revenue, our business and our results of operations.

To gain approval to market our tumor-specific immunotherapy product candidates, we must provide the FDA and foreign regulatory authorities with clinical data that adequately demonstrate the safety and efficacy of the product candidate for the intended indication applied for in the applicable regulatory filing. Product development is a long, expensive and uncertain process, and delay or failure can occur at any stage of any of our clinical development programs. A number of companies in the biotechnology and pharmaceutical industries have suffered significant setbacks in clinical trials, even after promising results in earlier preclinical or clinical trials. These setbacks have been caused by, among other things, preclinical findings made while clinical studies were underway and safety or efficacy observations made in clinical trials, including previously unreported adverse events. Success in preclinical testing and early clinical trials does not ensure that later clinical trials will be successful, and the results of clinical trials by other parties may not be indicative of the results in trials we may conduct.

We have not previously submitted a BLA or any other marketing application to the FDA or similar filings to comparable foreign regulatory authorities. A BLA or other similar regulatory filing requesting approval to market a product candidate must include extensive preclinical and clinical data and supporting information to establish that the product candidate is safe, pure and potent for each desired indication. The BLA or other similar regulatory filing must also include significant information regarding the chemistry, manufacturing and controls for the product.

The research, testing, manufacturing, labeling, approval, sale, marketing and distribution of biologic products are subject to extensive regulation by the FDA and other regulatory authorities in the United States and other countries, and such regulations differ

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from country to country. We are not permitted to market our product candidates in the United States or in any foreign countries until they receive the requisite approval from the applicable regulatory authorities of such jurisdictions.

The FDA or any foreign regulatory bodies can delay, limit or deny approval of our product candidates for many reasons, including:

Of the large number of biopharmaceutical products in development, only a small percentage successfully complete the FDA or other regulatory bodies’ approval processes and are commercialized.

Even if we eventually complete clinical testing and receive approval from the FDA or applicable foreign agencies for any of our product candidates, the FDA or the applicable foreign regulatory agency may grant approval contingent on the performance of costly additional clinical trials which may be required after approval. The FDA or the applicable foreign regulatory agency also may approve our lead product candidate for a more limited indication or a narrower patient population than we originally requested, and the FDA, or applicable foreign regulatory agency, may not approve our product candidates with the labeling that we believe is necessary or desirable for the successful commercialization of such product candidates.

Any delay in obtaining, or inability to obtain, applicable regulatory approval would delay or prevent commercialization of our product candidates and would materially adversely impact our business and prospects.

We have chosen to prioritize development of our personalized immunotherapy candidate, GRANITE, and our off-the-shelf immunotherapy candidate, SLATE. We may expend our limited resources on candidates or indications that do not yield a successful product and fail to capitalize on other product candidates or indications for which there may be a greater likelihood of success or may be more profitable.

We have initially developed our GRANITE personalized cancer immunotherapy candidates based on the prediction of a patient’s TSNA, in order to address a variety of cancers, including metastatic non-small cell lung cancer, or NSCLC, and gastroesophageal, bladder and colorectal cancers. GRANITE is now being evaluated in the Phase 2 portion of the GO-004 trial, which started enrolling patients in Q3 2020 with an objective to identify interpretable signals of efficacy when combining our vaccine candidate with immune checkpoint inhibitors with a focus on tumor types that do not respond to immune checkpoint inhibitors (MSS colorectal cancers), respond poorly (gastroesophageal cancers) or have progressed after first line therapy with immune checkpoint inhibitors (NSCLC). The clinical trial of SLATE, our off-the-shelf product candidate is currently evaluating subjects with mutation positive and metastatic and advanced solid tumors, including NSCLC, colorectal and pancreatic cancers. SLATE is now being evaluated in the Phase 2 portion of the GO-005 trial, which is now focusing on patients with NSCLC while we are preparing an improved KRAS-focused cassette to treat patients with KRAS-positive tumors, and will resume accrual of patients with pancreatic and colorectal cancer once this new version of the product candidate is available in the first half of 2021. We have strategically determined to initially focus solely on the development of personalized cancer immunotherapy candidates (including our “off-the-shelf” immunotherapy candidate) rather than pursue other types of immunotherapies based, in part, on the significant resources required to develop and manufacture immunotherapies. As a result, we may initially be foregoing other potentially more profitable therapy indications or those with a greater likelihood of success.

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Our decisions concerning the allocation of research, development, collaboration, management and financial resources toward particular product candidates or therapeutic areas may not lead to the development of any viable commercial product and may divert resources away from better opportunities. Similarly, our potential decisions to delay, terminate or collaborate with third parties in respect of certain programs may subsequently also prove to be suboptimal and could cause us to miss valuable opportunities. If we make incorrect determinations regarding the viability or market potential of any of our programs or product candidates or misread trends in the oncology or biopharmaceutical industry, our business, financial condition and results of operations could be materially adversely affected. As a result, we may fail to capitalize on viable commercial products or profitable market opportunities, be required to forego or delay pursuit of opportunities with other product candidates or other diseases and disease pathways that may later prove to have greater commercial potential than those we choose to pursue, or relinquish valuable rights to such product candidates through collaboration, licensing or other royalty arrangements in cases in which it would have been advantageous for us to invest additional resources to retain development and commercialization rights.

If we are unable to obtain regulatory approval for use of our tumor-specific immunotherapy candidates, GRANITE and SLATE, as a first- and second-line therapy, our commercial opportunity and profitability may be limited.

Cancer therapies for advanced/metastatic cancers are sometimes characterized as first line, second line or third line, and the FDA often approves new systemic therapies initially only for third line use. When cancer is detected early enough, surgery plus first-line systemic therapy is sometimes adequate to cure the cancer. Whenever first-line therapy, usually chemotherapy, hormone therapy, radiotherapy, surgery or a combination of these, proves unsuccessful, second line therapy may be administered. Second-line therapies often consist of more chemotherapy, radiation, antibody drugs, tumor targeted small molecules or a combination of these. Third-line therapies can include bone marrow transplantation, antibody and small molecule targeted therapies and new technologies such as adoptive cell therapies.

Traditionally, novel therapeutics are developed and approved in late (third) line therapy of cancer patients. Such clinical programs carry risk of failure because patients are often quite frail, with effects of multiple rounds of prior therapy weakening bone marrow, immune systems and general fitness. Immunotherapy, such as checkpoint inhibitors, has generally been shown to be more effective when used in earlier lines of therapy, with prospect of very durable responses in some patients; and, there is a trend towards earlier use of these agents, avoiding in particular cytotoxic chemotherapy agents which carry substantial toxicity and very little prospect of long-term responses. Our clinical development program also aims to study our products in early stages of cancer treatment (referred to as, adjuvant therapy), which carry a higher safety bar, and often a greater expectation of efficacy over control arms. Such studies may thus be relatively large and slow to achieve maturity. There are new tools available to stratify cancer patients for risk of recurrence or progression, such as liquid biopsies that measure the amount of circulating tumor-derived DNA. We will utilize these tools to attempt to expedite clinical trials in early-stage cancer patients by focusing upon patients at above-average risk of disease recurrence or progression, which events are typical endpoints in clinical trials. The development of liquid biopsies is at an early stage, however, and these tools may prove to carry low utility and thus render early-stage cancer trials slow, necessarily large and expensive. The safety of our product candidates in combination with checkpoint inhibitors in early lines of therapy may also prove to be unacceptable.

We expect to seek approval of our product candidates both as late-line therapy where appropriate, but also as a second line and first line therapy wherever possible and potentially as adjuvant therapy. There is no guarantee that our product candidates, even if approved in late-line therapy, would be approved for second-line or first-line or adjuvant therapy. In addition, we may have to conduct additional clinical trials prior to gaining approval for second-line or first-line or adjuvant therapy.

While our SLATE product is designed to be readily available (off-the-shelf), GRANITE will initially take approximately 14-18 weeks post-sequencing to be manufactured and released for human use, and this long timeline demands that either patients are consented and entered into our trials when they start a prior line of therapy, and start our therapy upon disease progression, or we initiate treatment in patients who have entered the maintenance phase of their original line of treatment. For example, we might enroll newly diagnosed patients who are due to receive front-line chemotherapy and then start their therapy with our immunotherapy product candidate as second-line treatment when they progress upon front-line chemotherapy or fail to tolerate it. This carries the risk of time delays or drop-out, i.e. patients may not progress after first-line chemotherapy for a long time, or they may decide not to receive an immunotherapy product candidate we have manufactured for them, at our expense. Alternatively, we may treat first-line patients once they have completed their initial treatment and have not progressed (called maintenance therapy)—this renders efficacy harder to interpret versus simple treatment studies (any objective response cannot clearly be attributed to our products) and may be complicated by standard of care treatments which may necessarily be continued alongside our immunotherapy candidates, further confounding interpretation of efficacy.

Our projections of both the number of people who have the cancers we are targeting, as well as the subset of people with these cancers in a position to receive third-line therapy and who have the potential to benefit from treatment with our product

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candidates, are based on our beliefs and estimates. These estimates have been derived from a variety of sources, including scientific literature, surveys of clinics, patient foundations, and market research and may prove to be incorrect. Regulatory authorities also may establish narrower definitions around when a patient is ineligible for other treatments than we have used in our projections, and that would reduce the size of the patient population eligible for our product candidates. Further, new studies may change the estimated incidence or prevalence of these cancers. The number of patients may turn out to be lower than expected. Additionally, the potentially addressable patient population for our product candidates may be limited or may not be amenable to treatment with our product candidates. For instance, we anticipate that only a fraction of colorectal cancer patients will be predicted to have a high enough probability of TSNA presence to merit their inclusion into our program. Even if we obtain significant market share for our product candidates, because the potential target populations are small, we may never achieve profitability without obtaining regulatory approval for additional indications, including use as a first-line or second-line therapy.

If we encounter difficulties enrolling patients in our clinical trials, our clinical development activities could be delayed or otherwise adversely affected.

The timely completion of clinical trials in accordance with their protocols depends, among other things, on our ability to enroll a sufficient number of patients who remain in the study until its conclusion. We may experience difficulties in patient enrollment in our clinical trials for a variety of reasons. The enrollment of patients depends on many factors, including:

In addition, our clinical trials may compete with other clinical trials for product candidates that are in the same therapeutic areas as our product candidates, and this competition will reduce the number and types of patients available to us, because some patients who might have opted to enroll in our trials may instead opt to enroll in a trial being conducted by one of our competitors. As a result of the COVID-19 pandemic, we have continued to experience delays in patient enrollment and challenges in monitoring patients once on study. We anticipate facing additional challenges if the COVID-19 pandemic continues or worsens. In particular, patients may elect to receive a chimpanzee adenovirus-based COVID-19 vaccine, which may delay their eligibility to receive our vaccine candidate by at least 4 months.

Further, the targeting of TSNA may result in unforeseen events, including harming healthy tissues in humans. As a result, it is possible that safety concerns could negatively affect patient enrollment among the patient populations that we intend to treat. Delays in patient enrollment may result in increased costs or may affect the timing or outcome of the planned clinical trials, which could prevent completion of these trials and adversely affect our ability to advance the development of our product candidates.

Our tumor-specific immunotherapy product candidates may cause undesirable side effects or have other properties that could delay or prevent their regulatory approval, limit the commercial profile of an approved label, or result in significant negative consequences following marketing approval, if any.

As with most biological products, use of our product candidates could be associated with side effects or adverse events which can vary in severity from minor reactions to death and in frequency from infrequent to prevalent. Undesirable side effects or unacceptable toxicities caused by our product candidates could cause us or regulatory authorities to interrupt, delay or halt clinical trials and could result in a more restrictive label or the delay or denial of regulatory approval by the FDA or comparable foreign regulatory authorities. While we have now completed the Phase 1 portions of our clinical trials of GRANITE and SLATE, we do not yet have a comprehensive understanding of their risks, and it is likely that there will be side effects associated with their use in

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increasing numbers of patients in Phase 2 and beyond. Results of our trials could reveal a high and unacceptable severity and prevalence of these or other side effects.

If unacceptable side effects arise in the development of our product candidates, we, the FDA, the IRBs at the institutions in which our studies are conducted, or the DSMB could suspend or terminate our clinical trials or the FDA or comparable foreign regulatory authorities could order us to cease clinical trials or deny approval of our product candidates for any or all targeted indications. Treatment-related side effects could also affect patient recruitment or the ability of enrolled patients to complete any of our clinical trials or result in potential product liability claims. In addition, these side effects may not be appropriately recognized or managed by the treating medical staff. We expect to have to train medical personnel using our product candidates to understand the side effect profiles for our clinical trials and upon any commercialization of any of our product candidates. Inadequate training in recognizing or managing the potential side effects of our product candidates could result in patient injury or death. Any of these occurrences may harm our business, financial condition and prospects significantly.

In addition, even if we successfully advance one of our tumor-specific immunotherapy product candidates through clinical trials, such trials will likely only include a limited number of subjects and limited duration of exposure to our product candidates. As a result, we cannot be assured that adverse effects of our product candidates will not be uncovered when a significantly larger number of patients are exposed to the product candidate. Further, any clinical trials may not be sufficient to determine the effect and safety consequences of taking our product candidates over a multi-year period.

If any of our product candidates receives marketing approval and we or others later identify undesirable side effects caused by such products, a number of potentially significant negative consequences could result, including:

Any of the foregoing events could prevent us from achieving or maintaining market acceptance of the particular product candidate, if approved, and result in the loss of significant revenues to us, which would materially and adversely affect our results of operations and business. In addition, if one or more of our product candidates or our TSNA-directed immunotherapy approach generally prove to be unsafe, our entire technology platform and pipeline could be affected, which would have a material and adverse effect on our business, financial condition, results of operations and prospects.

Even if one of our tumor-specific immunotherapy product candidates obtains regulatory approval, it may fail to achieve the broad degree of physician and patient adoption and use necessary for commercial success.

Even if one of our tumor-specific immunotherapy product candidates receives FDA or other regulatory approvals, the commercial success of any of our current or future product candidates will depend significantly on the broad adoption and use of the resulting product by physicians and patients for approved indications. The degree and rate of physician and patient adoption of our current or future product candidates, if approved, will depend on a number of factors, including:

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We cannot assure you that our current or future product candidates, if approved, will achieve broad market acceptance among physicians and patients. Any failure by our product candidates that obtain regulatory approval to achieve market acceptance or commercial success would adversely affect our results of operations.

We currently perform the majority of the manufacturing of our initial product candidates internally and rely on qualified third parties to supply some components of our initial product candidates. Our inability to manufacture sufficient quantities of GRANITE, SLATE or any future product candidates, or the loss of our third-party suppliers, or our or their failure to comply with applicable regulatory requirements or to supply sufficient quantities at acceptable quality levels or prices, or at all, would materially and adversely affect our business.

Manufacturing is a vital component of our tumor-specific immunotherapy approach and we have invested significantly in our manufacturing facility. To ensure timely and consistent product supply assurance to our patients we previously used a hybrid product supply approach whereby certain elements of our initial product candidates were manufactured internally at our manufacturing facilities in Pleasanton, California, and other elements were manufactured at qualified third-party contract manufacturing organizations, or CMOs. All internal and third-party contract manufacturing is performed under cGMP guidelines. We have internalized a majority of the manufacturing steps to optimize cost and production time, as well as establish full control over intellectual property and product quality. We will need to continue to scale up our manufacturing operations, as we continue to build the infrastructure and improve the capability internally to manufacture all supplies needed for our product candidates or the materials necessary to produce our product candidates for use in the conduct of our preclinical studies or clinical trials. We currently lack the internal resources and the capability to manufacture certain elements of our product candidates on a clinical scale. Accordingly, we have made, and will be required to continue to make, significant investments in our manufacturing facility and processing in the future, and our efforts to scale our manufacturing operations may not succeed.

In addition, our facilities and the facilities used by our CMOs to manufacture our product candidates are subject to various regulatory requirements and may be subject to the inspection of the FDA or other regulatory authorities. We do not control the manufacturing process at our CMOs and are completely dependent on them for compliance with current regulatory requirements. If we or our CMOs cannot successfully manufacture material that conforms to our specifications and the strict regulatory requirements

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of the FDA or comparable regulatory authorities in foreign jurisdictions, we may not be able to rely on our or their manufacturing facilities for the manufacture of elements of our product candidates. In addition, we have limited control over the ability of our CMOs to maintain adequate quality control, quality assurance and qualified personnel. If the FDA or a comparable foreign regulatory authority finds our facilities or those of our CMOs inadequate for the manufacture of our product candidates or if such facilities are subject to enforcement action in the future or are otherwise inadequate, we may need to find alternative manufacturing facilities, which would significantly impact our ability to develop, obtain regulatory approval for or market our product candidates.

Additionally, we and our CMOs may experience manufacturing difficulties due to resource constraints, as a result of labor disputes or unstable political environments, or due to the impact of the COVID-19 pandemic. If we or our CMOs were to encounter any of these difficulties, our ability to provide our product candidates to patients in clinical trials, or to provide product for the treatment of patients once approved, would be jeopardized.

Our tumor-specific product candidates are biologics with complex and time-consuming manufacturing processes, and we may encounter difficulties in production, particularly with respect to process development or scaling-out of our manufacturing capabilities. If we or any of our third-party manufacturers encounter such difficulties, our ability to provide supply of our product candidates for clinical trials or our products for patients, if approved, could be delayed or stopped, or we may be unable to maintain a commercially viable cost structure.

Our tumor-specific immunotherapy product candidates, GRANITE and SLATE, are considered to be biologics, and the manufacturing processes are complex, time-consuming, highly-regulated and subject to multiple risks. SLATE is designed using known genetic sequences available from public databases, while the manufacture of our product candidate GRANITE involves extraction of genetic material from patient tumor samples. Both GRANITE and SLATE require genetic manipulations at the gene sequence level, live cell culture operations, specialized formulations and aseptic fill finish operations. As a result of these complexities, the cost to manufacture biologics in general, and our personalized immunotherapy GRANITE in particular, is generally higher than traditional small molecule chemical compounds, and the manufacturing process is less reliable and more difficult and time-consuming to reproduce. For example, the entire cGMP manufacturing process, from biopsy receipt and sequencing completion to the release and shipment of GRANITE to the clinical site for patient administration, will initially take approximately 14-18 weeks. In addition, our manufacturing process for both GRANITE and SLATE are in their early stages of development and will be susceptible to product loss or failure, or product variation that may adversely impact patient outcomes. Our supply chain may not function efficiently due to logistical issues associated with but not limited to the collection of a tumor biopsy from the patient, shipping such material to the manufacturing site, sequencing the biopsy specimen, manufacturing the immunotherapy components, shipping the final immunotherapy back to the patient, and injecting the patient with the immunotherapy. Manufacturing issues or different product characteristics resulting from process development activities or even minor deviations during normal manufacturing processes could result in reduced production yields, product defects and other supply disruptions. If for any reason we lose a patient’s biopsy or an in-process product at any point in the process, the manufacturing process for that patient will need to be restarted and the resulting delay may adversely affect that patient’s outcome. Because GRANITE is manufactured specifically for an individual patient, we will be required to maintain a chain of identity and chain of custody with respect to materials as they move from the patient to the manufacturing facility, through the manufacturing process, and back to the patient. Maintaining such a chain of identity and chain of custody is difficult and complex, and the failure to do so could result in adverse patient outcomes, loss of product or regulatory action including withdrawal of our products from the market, if licensed.

As part of our process development efforts for GRANITE and SLATE, we also may make changes to our manufacturing processes at various points during development, for various reasons, such as controlling costs, achieving scale, decreasing processing time, increasing manufacturing success rate, or other reasons. Such changes carry the risk that they will not achieve their intended objectives, and any of these changes could cause our product candidates to perform differently and affect the results of our ongoing clinical trials or future clinical trials. In some circumstances, changes in the manufacturing process may require us to perform ex vivo comparability studies and to collect additional data from patients prior to undertaking more advanced clinical trials. For instance, changes in our process during the course of clinical development may require us to show the comparability of the product used in earlier clinical phases or at earlier portions of a trial to the product used in later clinical phases or later portions of the trial.

Furthermore, if microbial, viral or other contaminations are discovered in our supply of our product candidates or in our manufacturing facilities, or those of our CMOs, such manufacturing facilities may need to be closed for an extended period of time to investigate and remedy the contamination. We cannot assure you that any such contaminations or stability failures or other issues relating to the manufacture of our product candidates will not occur in the future.

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We depend on third-party suppliers for key materials used in our manufacturing processes, and the loss of these third-party suppliers or their inability to supply us with adequate materials could harm our business.

We rely on third-party suppliers for certain materials required for the production of our personalized immunotherapy candidate. Our dependence on these third-party suppliers and the challenges we may face in obtaining adequate supplies of materials involve several risks, including limited control over pricing, availability, quality and delivery schedules. As a small company, our negotiation leverage is limited, and we are likely to get lower priority than our larger competitors. We cannot be certain that our suppliers will continue to provide us with the quantities of these raw materials that we require or satisfy our anticipated specifications and quality requirements, particularly if the COVID-19 pandemic continues or worsens. Any supply interruption in limited or sole sourced raw materials could materially harm our ability to manufacture our product candidates until a new source of supply, if any, could be identified and qualified. We may be unable to find a sufficient alternative supply channel in a reasonable time or on commercially reasonable terms. Any performance failure on the part of our suppliers could delay the development and potential commercialization of our product candidates, including limiting supplies necessary for clinical trials and regulatory approvals, which would have a material adverse effect on our business.

We rely on third parties in the conduct of all of our preclinical studies and intend to rely on third parties in the conduct of all of our future clinical trials. If these third parties do not successfully carry out their contractual duties, fail to comply with applicable regulatory requirements or meet expected deadlines, we may be unable to obtain regulatory approval for our tumor-specific immunotherapy product candidates.

We currently do not have the ability to independently conduct preclinical studies that comply with the regulatory requirements known as good laboratory practice, or GLP, requirements. We also do not currently have the ability to independently conduct any clinical trials. The FDA and regulatory authorities in other jurisdictions require us to comply with regulations and standards, commonly referred to as good clinical practice, or GCP, requirements for conducting, monitoring, recording and reporting the results of clinical trials, in order to ensure that the data and results are scientifically credible and accurate and that the trial subjects are adequately informed of the potential risks of participating in clinical trials. We rely on medical institutions, clinical investigators, contract laboratories and other third parties, such as CROs, to conduct GLP-compliant preclinical studies and GCP-compliant clinical trials on our product candidates properly and on time. While we have agreements governing their activities, we control only certain aspects of their activities and have limited influence over their actual performance. The third parties with whom we contract for execution of our GLP-compliant preclinical studies and our GCP-compliant clinical trials play a significant role in the conduct of these studies and trials and the subsequent collection and analysis of data. These third parties are not our employees and, except for restrictions imposed by our contracts with such third parties, we have limited ability to control the amount or timing of resources that they devote to our programs. Although we rely on these third parties to conduct our GLP-compliant preclinical studies and GCP-compliant clinical trials, we remain responsible for ensuring that each of our preclinical studies and clinical trials is conducted in accordance with its investigational plan and protocol and applicable laws and regulations, and our reliance on the CROs does not relieve us of our regulatory responsibilities.

Many of the third parties with whom we contract may also have relationships with other commercial entities, including our competitors, for whom they may also be conducting clinical trials or other drug development activities that could harm our competitive position. Further, under certain circumstances, these third parties may terminate their agreements with us upon as little as 10 days’ prior written notice. Some of these agreements may also be terminated by such third parties under certain other circumstances, including our insolvency. If the third parties conducting our preclinical studies or our clinical trials do not adequately perform their contractual duties or obligations, experience significant business challenges, disruptions or failures, do not meet expected deadlines, terminate their agreements with us or need to be replaced, or if the quality or accuracy of the data they obtain is compromised due to their failure to adhere to our protocols or to GLPs/GCPs, or for any other reason, we may need to enter into new arrangements with alternative third parties. This could be difficult, costly or impossible, and our preclinical studies or clinical trials may need to be extended, delayed, terminated or repeated. As a result, we may not be able to obtain regulatory approval in a timely fashion, or at all, for the applicable product candidate, our financial results and the commercial prospects for our product candidates would be harmed, our costs could increase, and our ability to generate revenues could be delayed.

Disruptions at the FDA and other government agencies caused by funding shortages or global health concerns could hinder their ability to hire, retain or deploy key leadership and other personnel, or otherwise prevent new or modified products from being developed, approved or commercialized in a timely manner or at all, which could negatively impact our business.

The ability of the FDA to review and approve new products can be affected by a variety of factors, including government budget and funding levels, statutory, regulatory and policy changes, the FDA’s ability to hire and retain key personnel and accept the payment of user fees, and other events that may otherwise affect the FDA’s ability to perform routine functions. Average review times at the FDA have fluctuated in recent years as a result. In addition, government funding of other government agencies that fund research and development activities is subject to the political process, which is inherently fluid and unpredictable. Disruptions at the

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FDA and other agencies may also slow the time necessary for new biologics or modifications to approved biologics to be reviewed and/or approved by necessary government agencies, which would adversely affect our business. For example, over the last several years, including for 35 days beginning on December 22, 2018, the U.S. government has shut down several times and certain regulatory agencies, such as the FDA, have had to furlough critical FDA employees and stop critical activities.

Separately, in response to the COVID-19 pandemic, on March 10, 2020 the FDA announced its intention to postpone most inspections of foreign manufacturing facilities and products, and on March 18, 2020 the FDA temporarily postponed routine surveillance inspections of domestic manufacturing facilities. Subsequently, on July 10, 2020, the FDA announced its intention to resume certain on-site inspections of domestic manufacturing facilities subject to a risk-based prioritization system. The FDA intends to use this risk-based assessment system to identify the categories of regulatory activity that can occur within a given geographic area, ranging from mission critical inspections to resumption of all regulatory activities. Regulatory authorities outside the United States may adopt similar restrictions or other policy measures in response to the COVID-19 pandemic. If a prolonged government shutdown occurs, or if global health concerns continue to prevent the FDA or other regulatory authorities from conducting their regular inspections, reviews or other regulatory activities, it could significantly impact the ability of the FDA or other regulatory authorities to timely review and process our regulatory submissions, which could have a material adverse effect on our business.

We face significant competition in an environment of rapid technological and scientific change, and our failure to effectively compete may prevent us from achieving significant market penetration. Most of our competitors have significantly greater resources than we do, and we may not be able to successfully compete.

The biotechnology and pharmaceutical industries in particular are characterized by rapidly advancing technologies, intense competition and a strong emphasis on developing proprietary therapeutics. We compete with a variety of multinational biopharmaceutical companies and specialized biotechnology companies, as well as technology being developed at universities and other research institutions. Our competitors have developed, are developing or will develop product candidates and processes competitive with our product candidates. Competitive therapeutic treatments include those that have already been approved and accepted by the medical community and any new treatments that enter the market. We believe that a significant number of product candidates are currently under development, and may become commercially available in the future, for the treatment of diseases and

other conditions for which we may try to develop product candidates. There is intense and rapidly evolving competition in the biotechnology, biopharmaceutical and antibody and immunoregulatory therapeutics fields. We believe that while our discovery platform, its associated intellectual property and our scientific and technical know-how give us a competitive advantage in this space, competition from many sources remains. Our competitors include larger and better funded biopharmaceutical, biotechnological and therapeutics companies. Moreover, we also compete with current and future therapeutics developed at universities and other research institutions.

Our success will partially depend on our ability to develop and protect therapeutics that are safer and more effective than competing products. Our commercial opportunity and success will be reduced or eliminated if competing products that are safer, more effective, or less expensive than the therapeutics we develop.

If either GRANITE or SLATE is approved, it will compete with a range of therapeutic treatments that are either in development or currently marketed. Indeed, a variety of oncology drugs and therapeutic biologics are on the market or in clinical development. Such marketed therapies range from immune checkpoint inhibitors such as Bristol-Myers Squibb Company’s OPDIVO and YERVOY, Merck & Co., Inc.’s KEYTRUDA and Genentech, Inc.’s TECENTRIQ, and T cell engager immunotherapies such as Amgen, Inc.’s BLINCYTO. The most common therapeutic treatments for common solid tumors are chemotherapeutic compounds, radiation therapy, targeted therapies and now immunotherapies.

In addition, numerous compounds are in clinical development for cancer treatment. The clinical development pipeline for cancer includes small molecules, antibodies and immunotherapies from a variety of groups, including in the neoantigen space, the bispecific antibody space and engineered cell therapy and T cell receptor, or TCR, space. Many of these companies are well-capitalized and, in contrast to us, have significant clinical experience.

Many of our competitors have significantly greater financial, technical, manufacturing, marketing, sales and supply resources or experience than we do. If we successfully obtain approval for any product candidate, we will face competition based on many different factors, including the safety and effectiveness of our products, the ease with which our products can be administered and the extent to which patients accept relatively new routes of administration, the timing and scope of regulatory approvals for these products, the availability and cost of manufacturing, marketing and sales capabilities, price, reimbursement coverage and patent position. Competing products could present superior treatment alternatives, including by being more effective, safer, less expensive or marketed and sold more effectively than any products we may develop. Competitive products may make any products we develop obsolete or noncompetitive before we recover the expense of developing and commercializing our product candidates. Such

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competitors could also recruit our employees, which could negatively impact our level of expertise and our ability to execute our business plan.

The successful commercialization of our product candidates will depend in part on the extent to which governmental authorities, private health insurers, and other third-party payors provide coverage, adequate reimbursement levels and implement pricing policies favorable for our product candidates. Failure to obtain or maintain coverage and adequate reimbursement for our product candidates, if approved, could limit our ability to market those products and decrease our ability to generate revenue.

The availability of coverage and adequacy of reimbursement by managed care plans, governmental healthcare programs, such as Medicare and Medicaid, private health insurers and other third-party payors are essential for most patients to be able to afford medical services and pharmaceutical products such as our product candidates that receive FDA approval. Our ability to achieve acceptable levels of coverage and reimbursement for our products or procedures using our products by third-party payors will have an effect on our ability to successfully commercialize our product candidates. Obtaining coverage and adequate reimbursement for our products may be particularly difficult because of the higher prices often associated with drugs administered under the supervision of a physician. Separate reimbursement for the product itself or the treatment or procedure in which our product is used may not be available. A decision by a third-party payor not to cover or separately reimburse for our products or procedures using our products, could reduce physician utilization of our products once approved. Assuming there is coverage for our product candidates, or procedures using our product candidates by a third-party payor, the resulting reimbursement payment rates may not be adequate or may require co-payments that patients find unacceptably high. We cannot be sure that coverage and reimbursement in the United States, the European Union or elsewhere will be available for our product candidates or procedures using our product candidates, or any product that we may develop, and any reimbursement that may become available may not be adequate or may be decreased or eliminated in the future.

Third-party payors increasingly are challenging prices charged for pharmaceutical products and services, and many third-party payors may refuse to provide coverage and reimbursement for particular drugs or biologics when an equivalent generic drug, biosimilar or a less expensive therapy is available. It is possible that a third-party payor may consider our product candidates as substitutable and only offer to reimburse patients for the less expensive product. Even if we show improved efficacy or improved convenience of administration with our product candidates, pricing of existing third-party therapeutics may limit the amount we will be able to charge for our product candidates. These third-party payors may deny or revoke the reimbursement status of our product candidates, if approved, or establish prices for our product candidates at levels that are too low to enable us to realize an appropriate return on our investment. If reimbursement is not available or is available only at limited levels, we may not be able to successfully commercialize our product candidates and may not be able to obtain a satisfactory financial return on our product candidates.

There is significant uncertainty related to the insurance coverage and reimbursement of newly approved products, especially novel products like our immunotherapy product candidates. No regulatory authority has granted approval for a tumor-specific cancer immunotherapy based on a vaccine approach, and there is no model for reimbursement of this type of product. The Medicare and Medicaid programs increasingly are used as models in the United States for how private payors and other governmental payors develop their coverage and reimbursement policies for drugs and biologics. Some third-party payors may require pre-approval of coverage for new or innovative devices or drug therapies before they will reimburse healthcare providers who use such therapies. We cannot predict at this time what third-party payors will decide with respect to the coverage and reimbursement for our product candidates.

No uniform policy for coverage and reimbursement for products exists among third-party payors in the United States. Therefore, coverage and reimbursement for products can differ significantly from payor to payor. As a result, the coverage determination process is often a time-consuming and costly process that may require us to provide scientific and clinical support for the use of our product candidates to each payor separately, with no assurance that coverage and adequate reimbursement will be applied consistently or obtained in the first instance. Furthermore, rules and regulations regarding reimbursement change frequently, in some cases on short notice, and we believe that changes in these rules and regulations are likely.

Outside the United States, international operations are generally subject to extensive governmental price controls and other market regulations, and we believe the increasing emphasis on cost-containment initiatives in Europe and other countries have and will continue to put pressure on the pricing and usage of our product candidates. In many countries, the prices of medical products are subject to varying price control mechanisms as part of national health systems. Other countries allow companies to fix their own prices for medical products but monitor and control company profits. Additional foreign price controls or other changes in pricing regulation could restrict the amount that we are able to charge for our product candidates. Accordingly, in markets outside the United States, the reimbursement for our product candidates may be reduced compared with the United States and may be insufficient to generate commercially reasonable revenue and profits.

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Moreover, increasing efforts by governmental and third-party payors in the United States and abroad to cap or reduce healthcare costs may cause such organizations to limit both coverage and the level of reimbursement for newly approved products and, as a result, they may not cover or provide adequate payment for our product candidates. We expect to experience pricing pressures in connection with the sale of our product candidates due to the trend toward managed health care, the increasing influence of health maintenance organizations and additional legislative changes. The downward pressure on healthcare costs in general, particularly prescription drugs and biologics and surgical procedures and other treatments, has become intense. As a result, increasingly high barriers are being erected to the entry of new products.

If we are unable to support demand for our existing or future services, including ensuring that we have adequate capacity to meet increased demand, or we are unable to successfully manage the evolution of our EDGE platform, our business could suffer.

As the demand for our personalized and off-the-shelf immunotherapy candidates increases with our clinical trial needs, we will need to continue to increase our workflow capacity for sample intake and general process improvements, expand our internal quality assurance program, and apply our EDGE platform at a larger scale within expected turnaround times. We will need additional certified laboratory scientists and technicians and other scientific and technical personnel to process higher volumes of tumor biopsies. Portions of our process are not automated and will require additional personnel to scale. We will also need to purchase additional equipment, some of which can take several months or more to procure, set up, and validate, and increase our software and computing capacity to meet increased volume. There is no assurance that any of these increases in scale, expansion of personnel, equipment, software and computing capacities, or process enhancements will be successfully implemented, or that we will have adequate space in our laboratory facilities to accommodate such required expansion.

As we progress into clinical development and expand our manufacturing capabilities, we will need to incorporate new equipment, implement new technology systems and laboratory processes, and hire new personnel with different qualifications. Failure to manage this growth or transition could result in turnaround time delays, higher service costs, declining service quality, deteriorating customer service, and slower responses to competitive challenges. A failure in any one of these areas could make it difficult for us to meet market expectations for our services and could damage our reputation and the prospects for our business.

We currently have no sales organization. If we are unable to establish sales capabilities on our own or through third parties, we may not be able to market and sell our product candidates effectively in the United States and foreign jurisdictions, if approved, or generate product revenue.

We currently do not have a marketing or sales organization. In order to commercialize our product candidates, if approved, in the United States and foreign jurisdictions, we must build our marketing, sales, distribution, managerial and other non-technical capabilities or make arrangements with third parties to perform these services, and we may not be successful in doing so. If any of our product candidates receive regulatory approval, we expect to establish a sales organization with technical expertise and supporting distribution capabilities to commercialize each such product candidate, which will be expensive and time consuming. We have no prior experience in the marketing, sale and distribution of pharmaceutical products and there are significant risks involved in building and managing a sales organization, including our ability to hire, retain, and incentivize qualified individuals, generate sufficient sales leads, provide adequate training to sales and marketing personnel, and effectively manage a geographically dispersed sales and marketing team. Any failure or delay in the development of our internal sales, marketing and distribution capabilities would adversely impact the commercialization of these products. We may choose to collaborate with third parties that have direct sales forces and established distribution systems, either to augment our own sales force and distribution systems or in lieu of our own sales force and distribution systems. If we are unable to enter into such arrangements on acceptable terms or at all, we may not be able to successfully commercialize our product candidates. If we are not successful in commercializing our product candidates or any future product candidates, either on our own or through arrangements with one or more third parties, we may not be able to generate any

future product revenue and we would incur significant additional losses.

We will need to increase the size of our organization, and we may experience difficulties in managing growth.

As of December 31, 2020, we had 169 full-time employees. We will need to continue to expand our managerial, operational, finance and other resources in order to manage our operations and clinical trials, continue our development activities and commercialize our lead product candidate or any future product candidates. Our management and personnel, systems and facilities currently in place may not be adequate to support this future growth. Our need to effectively execute our growth strategy requires that we:

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If we fail to attract and retain senior management and key scientific personnel, our business may be materially and adversely affected.

Our success depends in part on our continued ability to attract, retain and motivate highly qualified management, clinical and scientific personnel. We are highly dependent upon our senior management, particularly our President and Chief Executive Officer, as well as our senior scientists and other members of our senior management team. The loss of services of any of these individuals could delay or prevent the successful development of our products, initiation or completion of our planned clinical trials or the commercialization of our lead product candidate or any future product candidates.

Competition for qualified personnel in the biotechnology and biopharmaceutical fields is intense due to the limited number of individuals who possess the skills and experience required by our industry. We will need to hire additional personnel as we expand our clinical development and if we initiate commercial activities. We may not be able to attract and retain quality personnel on acceptable terms, or at all. In addition, to the extent we hire personnel from competitors, we may be subject to allegations that they have been improperly solicited or that they have divulged proprietary or other confidential information, or that their former employers own their research output.

If product liability lawsuits are brought against us, we may incur substantial liabilities and may be required to limit commercialization of our current or future product candidates.

We face an inherent risk of product liability as a result of the planned clinical testing of our product candidates and will face an even greater risk if we commercialize any products. For example, we may be sued if any product we develop allegedly causes injury or is found to be otherwise unsuitable during product testing, manufacturing, marketing or sale. Any such product liability claims may include allegations of defects in manufacturing, defects in design, a failure to warn of dangers inherent in the product, negligence, strict liability, and a breach of warranty. Claims could also be asserted under state consumer protection acts. If we cannot successfully defend ourselves against product liability claims, we may incur substantial liabilities or be required to limit commercialization of our product candidates. Even successful defense would require significant financial and management resources. Regardless of the merits or eventual outcome, liability claims may result in:

Our inability to obtain and maintain sufficient product liability insurance at an acceptable cost and scope of coverage to protect against potential product liability claims could prevent or inhibit the commercialization of our current or any future product candidates we develop. We currently carry product liability insurance covering our clinical trials in the amount of $10.0 million in the aggregate. Although we maintain such insurance, any claim that may be brought against us could result in a court judgment or settlement in an amount that is not covered, in whole or in part, by our insurance or that is in excess of the limits of our insurance coverage. Our insurance policies also have various exclusions and deductibles, and we may be subject to a product liability claim for which we have no coverage. We will have to pay any amounts awarded by a court or negotiated in a settlement that exceed our coverage limitations or that are not covered by our insurance, and we may not have, or be able to obtain, sufficient funds to pay such

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amounts. Moreover, in the future, we may not be able to maintain insurance coverage at a reasonable cost or in sufficient amounts to protect us against losses. If and when we obtain approval for marketing any of our product candidates, we intend to expand our insurance coverage to include the sale of such product candidate; however, we may be unable to obtain this liability insurance on commercially reasonable terms or at all.

Our strategic collaborations, including those with Gilead and with bluebird as well as any future arrangements that we may enter into, may not be successful, which could significantly limit the likelihood of receiving the potential economic benefits of such collaborations and adversely affect our ability to develop and commercialize our product candidates.

In February 2021, we announced that we had entered into a collaboration, option and license agreement with Gilead to research and develop a vaccine for HIV. Under the terms of the agreement, Gilead will be responsible for conducting the Phase 1 study and, if it exercises its exclusive option, will develop and commercialize the HIV-specific therapeutic vaccine beyond Phase 1. In such case, and subject to certain clinical, regulatory and commercial milestones being achieved, Gritstone would receive up to an additional $725.0 million, as well as certain royalties on net sales upon commercialization. Separately, in August 2018, we entered into a strategic collaboration with bluebird to utilize our EDGE platform to identify and validate tumor-specific targets and provide TCRs directed to 10 selected targets for use in bluebird’s cell therapy products. Under that collaboration, we are entitled to receive up to an aggregate of $1.2 billion in development, regulatory and commercial milestones and tiered single digit royalties on sales of bluebird bio’s cell therapy products utilizing the TCRs we develop directed at the targets we discovered.

Apart from these strategic collaborations, in the future we may seek to enter into additional collaboration arrangements for the development or commercialization of certain of our product candidates depending on the merits of retaining commercialization rights for ourselves as compared to entering into collaboration arrangements. To the extent that we decide to enter into collaboration agreements in the future, we may face significant competition in seeking appropriate collaborators. Moreover, all such collaboration arrangements are complex and time-consuming to negotiate, document, implement and maintain, as well as challenging to manage. We may not be successful in our efforts with Gilead or bluebird, and we may never receive any of the payments contemplated in those collaboration arrangements. Further, we may be unable to prudently manage these collaborations or enter into new ones. The terms of any new collaborations or other arrangements that we may establish may not be favorable to us.

The success of our collaboration arrangements will depend heavily on the efforts and activities of our collaborators. Collaborations are subject to numerous risks, which may include risks that:

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If we engage in future acquisitions or strategic partnerships, this may increase our capital requirements, dilute our stockholders, cause us to incur debt or assume contingent liabilities, and subject us to other risks.

We may evaluate various acquisitions and strategic partnerships, including licensing or acquiring complementary products, intellectual property rights, technologies, or businesses. Any potential acquisition or strategic partnership may entail numerous risks, including:

In addition, if we undertake acquisitions, we may issue dilutive securities, assume or incur debt obligations, incur large one-time expenses and acquire intangible assets that could result in significant future amortization expense. Moreover, we may not be able to locate suitable acquisition opportunities, and this inability could impair our ab