Arcus Biosciences Discontinues Phase 3 STAR-221 Study With Gilead Following IDMC Futility Recommendation

• The Phase 3 STAR-221 study evaluating a domvanalimab-based combination in upper gastrointestinal cancers will be discontinued due to futility
• Arcus is continuing to expand its development program for casdatifan, a potential best-in-class HIF-2a inhibitor with robust single-agent activity, and multiple data readouts are expected in 2026
• Arcus's early development efforts will focus on five programs targeting inflammatory and autoimmune (I&I) diseases; a small molecule targeting MRGPRX2 is expected to enter the clinic in 2026
• With approximately $1B of cash and investmentsi, Arcus expects to be able to fund its planned operations until at least the second half of 2028

Arcus Biosciences, Inc. (NYSE:RCUS), a clinical-stage, global biopharmaceutical company focused on developing differentiated molecules and combination therapies for patients with cancer, inflammatory and autoimmune diseases, today announced the discontinuation of the Phase 3 STAR-221 study, being conducted in partnership with Gilead Sciences, Inc., due to futility. The decision is based on the recommendation from the Independent Data Monitoring Committee (IDMC) following its review of data from an event-driven, pre-specified interim analysis of overall survival (OS).

STAR-221 evaluated the anti-TIGIT antibody domvanalimab plus anti-PD-1 antibody zimberelimab and chemotherapy versus nivolumab plus chemotherapy as a first-line treatment for advanced gastric and esophageal cancers. At the interim analysis, the domvanalimab-based combination did not improve OS relative to that of nivolumab plus chemotherapy. The safety profile for the domvanalimab-based combination was similar to that of nivolumab plus chemotherapy, and there were no new safety findings identified.

The STAR-221 and the Phase 2 EDGE-Gastric studies will be discontinued, and Arcus and Gilead are communicating with investigators to determine appropriate next steps for patients in the study in addition to conducting a detailed analysis to better understand these results.