RCUS · Arcus Biosciences, Inc.

The discontinuation of the Phase 3 STAR-121 study represents a significant setback for Arcus Biosciences' clinical pipeline, specifically for its anti-TIGIT antibody domvanalimab in combination with zimberelimab and chemotherapy as a first-line treatment for metastatic non-small cell lung cancer. The decision, based on a pre-planned futility analysis recommended by the Independent Data Monitoring Committee, indicates the combination did not demonstrate sufficient efficacy to continue the trial. While safety was not assessed at this analysis, no new safety issues were identified during regular IDMC reviews. Concurrently, the announcement regarding Gilead's option rights highlights a shift in the collaboration dynamics. Gilead's decision not to make the option continuation payment results in the termination of its rights to additional early-stage programs, including CCR6, CD89, and CD40L, effective July 14, 2026. However, Gilead retains time-limited options to several other investigational assets, such as AB801, AB598, AB102, and a TNF small molecule inhibitor. Arcus maintains full control over the casdatifan program, except for rights licensed to Taiho in specific Asian territories. These developments collectively impact Arcus's near-term clinical prospects and partnership structure, with the STAR-121 discontinuation directly affecting a key late-stage asset and the Gilead update altering the scope of their collaborative pipeline.