GRANITE Vaccine Failure and Gritstone Bio's 2024 Bankruptcy

GRANITE was Gritstone bio's personalized mRNA cancer vaccine for patients with microsatellite stable (MSS) metastatic colorectal cancer — the roughly 90% of colorectal cancer cases that lack the heavy mutation burden which makes immunotherapy work in dMMR tumors. The vaccine used patient-specific neoantigens predicted by computational pipelines and delivered via a chimpanzee adenovirus prime followed by self-amplifying mRNA boost. In September 2024 the company reported Phase 2/3 interim results. Progression-free survival showed a hazard ratio of 0.79 — a numerical trend favoring the vaccine — but the 95% confidence interval ranged from 0.42 to 1.50, crossing 1.0 and therefore not statistically significant. The primary endpoint of molecular response was missed: 30% in the GRANITE arm versus 42% in the chemotherapy control arm, the wrong direction for a positive readout. The commercial consequences were swift. Gritstone filed for Chapter 11 bankruptcy protection on October 10, 2024. The company sold its main assets for approximately $21.25 million and emerged from bankruptcy in April 2025 in radically reduced form. The failure carries broader implications. It illustrates that the personalized-mRNA paradigm — which has shown promise in melanoma (Moderna mRNA-4157) and pancreatic cancer (BioNTech BNT122) — is not automatically transferable to MSS colorectal cancer, where the lower tumor mutational burden appears to limit the diversity and immunogenicity of neoantigens the algorithm can find. It also shows the brittle financing model of clinical-stage biotech: a single failed interim readout can destroy a company within weeks regardless of platform technology.