Gritstone Announces Dosing of First Solid Tumor Patient with Optimized SLATE “Off-the-Shelf” Mutant KRAS-directed Neoantigen Immunotherapy in Phase 2 Clinical Trial
- SLATE version (v) 1, Gritstone’s “off the-shelf" neoantigen immunotherapy (including KRAS, TP53 mutations), elicited multiple molecular responses and an unconfirmed RECIST radiologic response in patients with NSCLC who had progressed on prior immunotherapy
- SLATE v2 (a mutant KRAS-focused version), which is optimized for increased immune response, has been administered to the first patient in Phase 2 testing
The v1 format of the SLATE immunotherapy was studied in a Phase 1/2 study, in collaboration with Bristol-Myers Squibb, in 26 patients with metastatic solid tumors, largely focused on non-small cell lung cancer (NSCLC), microsatellite-stable colorectal cancer (MSS-CRC) and pancreatic ductal adenocarcinoma (PDAC). There were no safety signals of note with the most common adverse events being low grade, self-limiting fever and injection site reactions. SLATE v1 exhibited evidence of efficacy in patients with NSCLC who had all progressed on prior anti-PD-(L)1 therapy (often in combination with chemotherapy) – with molecular responses (>50% decrease in ctDNA levels in the blood from baseline) observed in 3/5 NSCLC patients who were eligible for analysis.
SLATE v1 demonstrated the greatest activity in 6 NSCLC patients with the KRASmut G12C presented by the HLA protein A*02:01. Among these patients, ctDNA responses were observed in 66% of these patients (2/3 eligible for analysis), correlating with clinical benefit, and a RECIST radiologic response (unconfirmed) was observed in one 2nd line patient who had progressed after 3 months of 1st line chemo-immunotherapy. One patient who had progressed on prior chemo-immunotherapy after 8 months of treatment is nearing completion of 2 years of therapy with persistent ~20% tumor lesion shrinkage. The patient’s ctDNA was undetectable throughout the study.
A next generation, optimized SLATE cassette (v2), which exclusively includes epitopes from mutated KRAS and exhibited immunogenic superiority over v1 in human HLA-transgenic mice, is now in Phase 2 testing in patients with advanced NSCLC and CRC.
“We are excited to dose the first patient with the KRAS-specific version (v2) of our SLATE immunotherapy,” said
The SLATE v2 Phase 2 portion of the study is expected to enroll up to 60 patients with KRAS mutant-driven tumors in total across three cohorts: NSCLC post chemo-immunotherapy, first line MSS-CRC and third-line MSS-CRC. All patients will receive SLATE v2, consisting of a dose of intramuscular adenovirus-based prime with intramuscular self-amplifying mRNA-based boost vaccinations, in combination with PD-1 checkpoint inhibitor Opdivo® (nivolumab) and subcutaneous anti-CTLA-4 antibody Yervoy® (ipilimumab).
Opdivo® and Yervoy® are trademarks of Bristol-Myers Squibb Company.
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, or TSNA, that are identified by the company using its proprietary Gritstone EDGETM artificial intelligence platform and tumor HLA peptide sequencing. Gritstone’s SLATE “off-the-shelf” immunotherapy uses a priming adenoviral vector (GRT-C903) and self-amplifying mRNA vector (GRT-R904) to deliver a cassette of shared TSNA, representing mutated gene sequences that are found in multiple patients (such as KRAS mutations). SLATE is being evaluated in combination with immune checkpoint blockade in the Phase 2 portion of its clinical study (NCT03953235).
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, including that interim results obtained may differ from those at completion of the studies and clinical trials. Such risks and uncertainties include, among others, the uncertainties inherent in the drug development process, including Gritstone’s programs’ early 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
Source: Gritstone bio, Inc.