Press Release Details

Nature Medicine Publishes Interim Results from Gritstone bio’s Phase 1/2 Study of GRANITE, Individualized Neoantigen Vaccine for Solid Tumors

August 15, 2022

-- Paper reports that Gritstone’s tumor-specific, neoantigen vaccination approach drives priming and boosting of tumor-specific T cells, including cytotoxic CD8+ T cells --

-- T cells linked to molecular responses in advanced colorectal cancer (CRC) patients and associated with extended overall survival, which has been observed in follow-up to the Phase 1/2 study --

-- GRANITE now in a randomized, controlled Phase 2/3 trial in newly diagnosed metastatic, microsatellite-stable colorectal cancer (MSS-CRC) with initial results expected 2H2023 --

EMERYVILLE, Calif., Aug. 15, 2022 (GLOBE NEWSWIRE) -- Gritstone bio, Inc. (Nasdaq: GRTS), a clinical-stage biotechnology company that aims to develop the world’s most potent vaccines, today announced that interim results from the Phase 1/2 trial of GRANITE, its individualized, vaccine-based immunotherapy candidate for solid tumor cancers, were published today in Nature Medicine. The paper, “Individualized, heterologous chimpanzee adenovirus and self-amplifying mRNA neoantigen vaccine for advanced metastatic solid tumors: phase 1 trial interim results,” details results demonstrating that GRANITE generated strong, persistent, and functional tumor-specific CD4+ and CD8+ T cell responses that have potential broad applicability across a range of disease settings. The published data were originally presented at the European Society for Medical Oncology (ESMO) Congress 2021, and acted as the basis for launching two randomized, controlled studies of GRANITE, including a Phase 2/3 trial that has registrational intent (GRANITE-CRC-1L).

“The publication of this study in Nature Medicine emphasizes the importance, novelty and potential clinical value of the GRANITE program, and reinforces our foundational hypothesis that targeting multiple neoantigens based on each individual tumor’s mutations could drive meaningful clinical benefit, including extended overall survival,” said Andrew Allen, M.D., Ph.D., Co-founder, President, and Chief Executive Officer of Gritstone. “Now we are advancing GRANITE into earlier disease settings, where immune responses are likely stronger, and patients generally have more time for immune destruction of tumors to take effect.”

Since initiation of the Phase 1/2 study, Gritstone has followed study participants and observed increased overall survival (OS) in colorectal cancer (CRC) patients who demonstrated a molecular response (measured by a reduction in circulating tumor DNA [ctDNA] levels from baseline) versus those who did not. As of May 2022, median OS of this subgroup (treated third-line CRC patients who demonstrated a molecular response) exceeded 18 months with the median not yet reached. This compares to median OS of 7.8 months for patients who did not demonstrate a molecular response, results which are generally consistent with extensive prior data from patients receiving various third-line therapies. Baseline characteristics of these two patient populations are similar. The Phase 1/2 study remains ongoing.

“Personalized neoantigen immunotherapy is a rational approach to treating solid tumor cancers given the abundant evidence that T cells can recognize neoantigens and drive tumor destruction,” said Karin Jooss, Ph.D., Executive Vice President, and Head of R&D. “We have carefully built the GRANITE platform and studied it in a translationally rich clinical program, demonstrating the sequence of desired biological events playing out in advanced cancer patients. Specifically, we showed de novo induction of neoantigen-specific T cells, trafficking of those same T cells to tumors, conversion of cold to hot tumor microenvironments, and key anti-tumor effects such as pseudo-progression, molecular responses, and suggestions of extended overall survival in molecular responders. In a tough tumor type such as metastatic colorectal cancer, these data are sufficiently striking to merit publication in Nature Medicine. We are proud of this accomplishment.”

GRANITE is now being evaluated in two randomized studies in earlier-stage disease; 1) GRANITE-CRC-1L (NCT05141721), a Phase 2/3 trial in newly diagnosed metastatic, microsatellite-stable colorectal cancer (MSS-CRC) that has registrational intent. The first patient was treated in this study in July 2022, and initial results from this study are expected in the second half of 2023. 2) GRANITE-ADJUVANT (NCT05456165), a phase 2 study in patients with high-risk stage II/III colon cancer who are ctDNA+ after definitive surgery.

Gritstone’s neoantigen-based immunotherapies are engineered to elicit a significant T cell response (particularly CD8+ cytotoxic T cells) against mutation-derived tumor-specific neoantigens (TSNA), that Gritstone identifies using its proprietary artificial intelligence platform, EDGE™. GRANITE is an individualized neoantigen-based immunotherapy and uses a priming adenoviral vector (GRT-C901) and self-amplifying mRNA vector (GRT-R902) to deliver personalized immunotherapy containing the relevant neoantigens. GRANITE was granted Fast Track designation by the U.S. Food and Drug Administration for the treatment of MSS-CRC.

About Gritstone
Gritstone bio, Inc. (Nasdaq: GRTS) is a clinical-stage biotechnology company that aims to create the world’s most potent vaccines. We leverage our innovative vectors and payloads to train multiple arms of the immune system to attack critical disease targets. Independently and with our collaborators, we are advancing a portfolio of product candidates to treat and prevent viral diseases and solid tumors in pursuit of improving patient outcomes and eliminating disease.

Gritstone Forward-Looking Statements
This press release contains forward-looking statements, including, but not limited to, statements related to the potential of Gritstone’s therapeutic programs; the advancements in the company’s ongoing clinical trials; the timing of data announcements related to ongoing clinical trials and the initiation of future clinical trials. Such forward-looking statements involve substantial risks and uncertainties that could cause Gritstone’s research and clinical development programs, future results, performance or achievements to differ significantly from those expressed or implied by the forward-looking statements. Such risks and uncertainties include, among others, the uncertainties inherent in the drug development process, including Gritstone’s programs’ clinical stage of development, the process of designing and conducting preclinical and clinical trials, the regulatory approval processes, the timing of regulatory filings, the challenges associated with manufacturing drug products, Gritstone’s ability to successfully establish, protect and defend its intellectual property and other matters that could affect the sufficiency of existing cash to fund operations. Gritstone undertakes no obligation to update or revise any forward-looking statements. For a further description of the risks and uncertainties that could cause actual results to differ from those expressed in these forward-looking statements, as well as risks relating to the business of the company in general, see Gritstone’s most recent Quarterly Report on Form 10-Q filed on August 4, 2022 and any current and periodic reports filed with the Securities and Exchange Commission.

Gritstone Contacts
Dan Budwick
(973) 271-6085

George E. MacDougall
Director, Investor Relations & Corporate Communications
Gritstone bio 

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