Gritstone bio Announces Positive Preliminary Progression-free Survival and Long-term Circulating Tumor DNA (ctDNA) Data from Phase 2 Portion of Ongoing Phase 2/3 Study of its Personalized Cancer Vaccine, GRANITE, in Front-line Metastatic Microsatellite St

-- Early progression-free survival (PFS) trends favor GRANITE recipients with hazard ratios of 0.82 in the overall population ([95% CI, 0.34-1.67]; 62% censored) and 0.52 (48% relative risk reduction of progression or death with GRANITE vs. control) in a high-risk group, where clinical data are more mature ([95% CI, 0.15-1.38]; 44% censored); >90% of high-risk patients have liver metastases --

-- Short-term molecular response (as defined by protocol) is uninformative due to an unexpectedly persistent ctDNA drop beyond induction chemotherapy; long-term circulating tumor DNA (ctDNA) responses align with PFS trends and favor GRANITE vs. control patients --

-- GRANITE was generally well-tolerated with manageable adverse events; no patients have discontinued GRANITE due to adverse events --

-- Mature PFS data expected in the third quarter of 2024; overall survival data expected in 1H 2025 --

EMERYVILLE, Calif., April 01, 2024 (GLOBE NEWSWIRE) -- Gritstone bio, Inc. (Nasdaq: GRTS), a clinical-stage biotechnology company working to develop the world’s most potent vaccines, today announced positive preliminary data from the ongoing, signal seeking Phase 2 portion of the Phase 2/3 study evaluating GRANITE, its personalized neoantigen cancer vaccine, in front-line metastatic microsatellite stable colorectal cancer (MSS-CRC). The randomized, controlled, open-label study is designed to quantify the clinical benefit of maintenance therapy with GRANITE (GRT-C901/GRT-R902) in combination with immune checkpoint blockade in addition to fluoropyrimidine/bevacizumab versus fluoropyrimidine/bevacizumab alone. Overall progression free survival (PFS) data show an early trend in benefit for GRANITE patients (HR=0.82, [95% CI, 0.34-1.67]; 62% censored) and extended PFS benefit in high-risk patients (HR=0.52 [95% CI, 0.15-1.38]; 44% censored), in whom progression occurs faster. Circulating tumor DNA (ctDNA) analysis over several months of treatment shows the expected relationship with disease progression and favors GRANITE, while short-term ctDNA response analysis (molecular response as defined per protocol) did not demonstrate a difference between study arms. Gritstone bio successfully manufactured GRANITE product candidate for every eligible patient (i.e., 100% vaccine manufacturing success rate).