Months after announcing the failure of a mid-stage trial for its personalized neoantigen vaccine in cancer, Gritstone bio reported more data that it plans to take to regulators.
In the Phase 2 trial, Gritstone’s GRANITE vaccine in addition to immune checkpoint inhibitors and standard chemotherapy showed a 21% relative risk reduction in disease progression or death versus chemo alone in 69 patients with frontline microsatellite stable colorectal cancer (HR=0.79). The study was “not statistically powered” for progression-free survival.
Even so, the company said Monday that signs of clinical benefit were greatest in the subset of patients with low disease burden, with that group seeing a 38% relative risk reduction of progression or death versus control (HR=0.62). It said it plans to keep following patients to establish a “plateau of improved PFS.”
Gritstone’s shares $GRTS were down around 20% on Tuesday morning.
Back in April, the Phase 2 trial missed its primary endpoint of short-term circulating tumor DNA response, with no difference seen between the treatment and control arms. At the time, CEO Andrew Allen said levels of the ctDNA biomarker dropped in patients in the control arm “for longer than we anticipated.”
Nonetheless, Gritstone plans to review the PFS data with the FDA “in the coming months” and decide on next steps for its vaccine, which could include a Phase 2 or 3 study with ctDNA as eligibility criteria.
But the company’s cash runway remains a challenge. It ended June with just $61.7 million in cash, equivalents, marketable securities and restricted cash. Gritstone disclosed Monday that it’s “reviewing potential value-maximizing strategies,” but won’t share any plans until it gets board approval. In March, the drugmaker laid off 40% of its staff after a delay for its Covid-19 vaccine trial.
As a personalized vaccine, GRANITE is designed to target patient-specific neoantigens that are predicted using tumor sequencing and the company’s EDGE platform technology.