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Gritstone Oncology Expands Into Phase II Studies With Neoantigen-based Immunotherapy

NEW YORK – Gritstone Oncology on Monday announced that it had begun dosing patients in the Phase II expansion cohorts of clinical trials evaluating its neoantigen-based immunotherapies GRANITE and SLATE.

The Phase II expansion comes in the wake of encouraging Phase I data, which demonstrated that the treatments were well-tolerated and elicited immune responses and early indications of efficacy across multiple cancer types. The Phase I portions of the trials are still ongoing, and Gritstone expects to present the full dataset by mid-2021.

For its part, the Phase II portion of the clinical trial evaluating GRANITE, dubbed GO-004, will be stratified into cohorts of patients with previously treated gastro-esophageal cancer and microsatellite-stable colorectal cancer. The trial is evaluating the combination of immune checkpoint inhibitors nivolumab and ipilimumab (Bristol Myers Squibb's Opdivo and Yervoy) with GRANITE, which is designed in a bespoke manner to target the unique peptide sequences in patients' tumors, in turn engendering an immune response from CD8+ T cells. For the selection of tumor-specific neoantigens, Gritstone uses its artificial intelligence-based Gritstone EDGE platform along with tumor HLA peptide sequencing.

In addition to GRANITE, the company is advancing its clinical trial of SLATE, an off-the-shelf version of GRANITE that shares the treatment's structure but is programmed to target pre-specified 20 tumor-specific neoantigens that are common across patients with specific cancers. The Phase II portion of the clinical trial evaluating SLATE, dubbed GO-005, will also evaluate the treatment in combination with BMS's checkpoint inhibitors, but will enroll and stratify patients based on the presence of molecular biomarkers. Specifically, Gritstone has begun enrolling patients with previously treated non-small cell lung cancer whose tumors harbor relevant KRAS mutations along with patients with multiple solid tumor histologies harboring a relevant TP53 mutation.

"The early Phase I data clearly show robust induction of neoantigen-specific CD8+ T cells, expansion of those cells in the tumor microenvironment, and early evidence of benefit to our patients," Daniel Catenacci, director of the Gastrointestinal Oncology Program at the University of Chicago Medicine and principal investigator of both studies, said in a statement. "Delivering effective immunotherapy to patients with cold tumors would change the landscape of cancer treatment and expand the role of immunotherapy significantly."