Gritstone Presentations at AACR Build Expertise in Neoantigen Vaccine Design and Delivery

— Translational immunology data and cassette design capabilities have enabled the development of an optimized, KRAS-specific version of a “ready-to-use” vaccine candidate currently in Phase 2 (SLATE-KRAS) —

— Neoantigen Individualized Therapeutic Vaccine Program (GRANITE) Data Support Circulating Tumor DNA (ctDNA) Response as a Predictor of Overall Survival in Metastatic Colorectal Cancer —

— Detailed Analysis of Oncology Programs Supports the Potency and Dose-Saving Potential of Self-Amplifying mRNA (samRNA) —

EMERYVILLE, Calif., April 12, 2022 (GLOBE NEWSWIRE) — Gritstone bio, Inc. GRTSa clinical-stage biotechnology company developing next-generation immunotherapies against cancer and infectious diseases, presented three presentations (one oral and two posters) further supporting the potential of its new vaccine development capabilities and delivery platforms to develop transformational therapeutic cancer vaccines at the 2022 American Association of Cancer Research (AACR) Annual Meeting.

“The collective data we presented at the AACR reinforces our expertise in the design and delivery of potent vaccines and supports the optimization of antigen cassette, dose and schedule design as key tools. to induce a differentiated immune response,” said Andrew Allen, MD, Ph.D., Co-Founder, President and CEO of Gritstone. “Vaccines targeting neoantigens identified from common tumor motor mutations are attracting increasing interest, and the presentation of our ‘off the shelf’ candidate for KRAS-specific mutations, SLATE-KRAS, demonstrates our ability to time to precisely define these targets and design the cassette and vaccine to optimize the immune response based on these specific mutations Early signals from our ongoing phase 2 study presented at AACR support the potential of SLATE-KRAS to drive stronger CD8+ T cell responses to mutant KRAS than our original candidate, SLATE v1. we look forward to further demonstrating the value of SLATE as evidence of clinical benefit.”

Oral presentation: Optimizing the design of shared neo-antigen vaccines to increase vaccine potency: from bench to bedside and back
Presenter: Christine D. Palmer, PhD

  • SLATE v1* was well tolerated and demonstrated a favorable safety profile in all treated subjects (n=26). The greatest activity was observed in six (6) NSCLC patients with KRASmute G12C mutations.
  • Gritstone then developed a second optimized product candidate (SLATE-KRAS) that exclusively includes mutated KRAS epitopes.
  • SLATE-KRAS is being evaluated in Phase 2 of a Phase 1/2 trial (NCT03953235), with initial data expected in the second half of 2022.

*SLATE v1 was administered in combination with Opdivo® (nivolumab) and subcutaneous anti-CTLA-4 antibody Yervoy® (ipilimumab). Opdivo® and Yervoy® are registered trademarks of Bristol-Myers Squibb Company.

Additional presentations at the AACR further elucidated the correlation between patient survival and circulating tumor DNA (ctDNA) in solid tumors (relevant to the company’s individualized vaccine program, GRANITE) and detailed a dose-response analysis, the results of which further support the potential dose economy of the company’s new vector that uses both oncology and infectious disease, self-amplified mRNA (samRNA).

Karin Jooss, Ph.D., Executive Vice President and Head of R&D added, “Clinical data from SLATE and GRANITE characterizing the optimal dosing regimen for our novel vector samRNA demonstrates more robust immune responses at lower doses, further supporting the overall potency and dose-sparing potential of samRNA. The collective data we presented at the AACR has read into our oncology and infectious disease pipeline programs, and further demonstrates Gritstone’s leadership in the field of neoantigen vaccines.

Poster presentation: Comprehensive ctDNA Monitoring Provides Early Signal of Clinical Benefit with Novel Neoantigen-Directed Personalized Immunotherapy for Patients With Advanced Cancer
Presenter: Matthew Davis, Ph.D.

  • The majority of neoantigens are retained in the tumor even after the patient has received treatment
  • Longitudinal ctDNA monitoring allows real-time assessment of response/resistance
  • Molecular response achieved in four (4) of nine (9) treated subjects, correlated with prolonged progression-free survival and overall survival, supports the clinical benefit of GRANITE in patients with advanced MSS-CRC

Poster presentation: Lower doses of self-amplified mRNA elicit superior neoantigen-specific CD8+ T cell responses in cancer patients compared to high doses
Presenter: Amy Rappaport, PhD

  • samRNA demonstrated a favorable safety profile at all 3 dose levels, with no evidence of increased reactogenicity with sequential doses
  • A lower dose of samRNA (30 μg) increased T-cell and humoral responses after a ChAd prime, whereas higher doses of samRNA (300 μg) only maintained the initial response to ChAd
  • Dose-dependent induction of IFN⍺ in cancer patients and non-human primates suggests inhibitory impact on early innate immune activation

To see Gritstone’s AACR presentations, visit

Gritstone’s neo-antigen immunotherapies are designed to elicit a significant T-cell (particularly CD8+ cytotoxic T-cell) response against mutation-derived tumor-specific neo-antigens, or TSNAs, that are identified by the company using its proprietary Gritstone EDGE™ artificial intelligence platform and tumor HLA peptide sequencing. SLATE, Gritstone’s “off-the-shelf” immunotherapy program, uses an adenoviral priming vector and a self-amplified mRNA vector to deliver a shared TSNA cassette, representing sequences of mutated genes that the found in several patients (such as KRAS mutations). SLATE is being evaluated in combination with immune checkpoint blockade in its Phase 2 clinical study (NCT03953235). Alongside the candidates developed to date, SLATE represents the potential to develop a suite of “off the shelf” product candidates that target tumor-specific mutations in a number of patient populations and cancer types.

About Gritstone
Gritstone Bio, Inc. GRTS, a clinical-stage biotechnology company, is developing the next generation of immunotherapies against multiple types of cancers and infectious diseases. Gritstone develops its products based on two key pillars: first, a proprietary artificial intelligence-based platform, Gritstone EDGE™, which is designed to predict antigens that are presented on the surface of cells, such as tumor or virus-infected cells, which can be seen by the immune system; and, second, the ability to develop and manufacture potent immunotherapies using these antigens to potentially drive the patient’s immune system to specifically attack and destroy disease-causing cells. The Company’s primary oncology programs include an individualized neoantigen immunotherapy, GRANITE, and a “ready-to-use” shared neoantigen immunotherapy, SLATE, which are being evaluated in clinical studies. In its infectious disease portfolio, Gritstone is advancing CORAL, a program providing self-amplified T cell-enhanced mRNA (samRNA) vaccines for COVID-19 that is supported by departments of the National Institutes of Health (NIH), the Bill & Melinda Gates Foundation, the Coalition for Epidemic Preparedness Innovations (CEPI), and through a licensing agreement with La Jolla Institute for Immunology. Additionally, the company has a global collaboration for the development of a therapeutic HIV vaccine with Gilead Sciences. For more information, please visit

Gritstone looking to the future Declarations
This press release contains forward-looking statements, including, but not limited to, statements related to the potential of Gritstone’s therapeutic programs; the progress of Gritstone’s ongoing clinical trials; the timing of data announcements related to ongoing clinical trials and the initiation of future clinical trials. These 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 materially from those expressed or implied by the forward-looking statements. These risks and uncertainties include, among others, the uncertainties inherent in the drug development process, including the early stage of development of Gritstone’s programs, the process for designing and conducting preclinical and clinical trials, the approval processes regulatory filings, the challenges associated with pharmaceutical manufacturing, Gritstone’s ability to successfully establish, protect and defend its intellectual property and other matters that could affect the sufficiency of existing liquidity to fund operations. Gritstone assumes no obligation to update or revise any forward-looking statements. For a more detailed 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 Gritstone’s business generally, see Gritstone’s most recent Annual Report on Form 10. -K filed March 10, 2022 and Gritstone’s future reports to be filed with the Securities and Exchange Commission. The forward-looking statements contained in this press release are based on information available to Gritstone as of the date hereof. Gritstone disclaims any obligation to update forward-looking statements, except as required by law.

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