Gritstone bio Announces Interim Phase 2 Data for GRANITE Individualized Neoantigen Targeting Immunotherapy in Frontline Metastatic Microsatellite Stable Colorectal Cancer

Gritstone bio
Gritstone bio
Gritstone bio
6 min read

In This Article:

--Encouraging progression-free survival data in overall population; continued follow-up needed to allow data to mature further, especially in low ctDNA subgroup where events accrue more slowly

--21% relative risk reduction of progression or death with GRANITE vs. control in all treated population (HR=0.79 [95% CI, 0.42-1.50])--

-- 38% relative risk reduction of progression or death with GRANITE vs. control in low ctDNA subgroup (HR=0.62 [95% CI, 0.23-1.70]) --

-- Strength of neoantigen specific T cell responses in GRANITE patients appears to associate with progression-free survival

-- GRANITE was generally well-tolerated with no treatment discontinuations due to adverse events–

-- Overall survival data expected in 2H 2025 --

EMERYVILLE, Calif., Sept. 30, 2024 (GLOBE NEWSWIRE) -- Gritstone bio, Inc. (Nasdaq: GRTS), a clinical-stage biotechnology company working to develop the world’s most potent vaccines, today announced encouraging interim Phase 2 data from the ongoing Phase 2 study evaluating GRANITE, its individualized neoantigen targeting immunotherapy, in frontline microsatellite stable colorectal cancer (MSS-CRC). The randomized, controlled study is designed to evaluate the clinical benefit of maintenance therapy with GRANITE (GRT-C901/GRT-R902) in combination with immune checkpoint inhibitors in addition to fluoropyrimidine/bevacizumab versus fluoropyrimidine/bevacizumab alone.

Overall progression-free survival (PFS) data show an encouraging benefit for GRANITE patients (HR=0.79 [95% CI, 0.42-1.50]). As expected, the greatest benefit was observed in the 50% of patients with lower disease burden at study entry, as measured by circulating tumor DNA (ctDNA) at study baseline. (HR=0.62 [95% CI, 0.23-1.70]). Continued follow-up is needed to fully assess GRANITE effects and determine whether a plateau of improved PFS (indicating durable clinical benefit) is achieved. The most recent ctDNA assessments for the 20 patients who remain without disease progression (per RECIST) were supportive of potential benefit from treatment with GRANITE: 12 of 13 GRANITE patients had stable ctDNA titers below the assay limit of quantitation (LOQ); 4 of 7 control patients exhibited the same characteristic.

“We are excited by the potential of GRANITE to extend both progression-free and overall survival in a disease where relentless progression is the rule with existing therapies,” said Andrew Allen, MD, PhD, Co-Founder, President & CEO of Gritstone bio. “The field of neoantigen-targeting immunotherapy is evolving rapidly, and the focus is shifting to patients with lower volume disease. Notably, patients with newly diagnosed metastatic disease who have low ctDNA at study entry and thereby relatively low disease burden, could benefit from this type of immunotherapy. Success for immunotherapy typically manifests as an elevated plateau in PFS and overall survival Kaplan-Meier curves, and we may be seeing this in our low disease burden population. We need more time to let these data mature. The most recent ‘low and stable’ ctDNA measurements in most GRANITE patients are encouraging since that pattern is not typically seen in patients about to develop disease progression. The potential PFS benefit observed in MSS-CRC, a notoriously ‘cold’ tumor, suggests opportunity for even greater effects in tumors more typically amenable to immunotherapy.”

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