Arcus Biosciences, Inc. (NYSE:RCUS) on Friday announced the discontinuation of the Phase 3 STAR-221 study, being conducted in partnership with Gilead Sciences, Inc. (NASDAQ:GILD), due to futility.
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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 for untreated patients with 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.
Casdatifan and Clear Cell Renal Cell Carcinoma (ccRCC) Patients
Arcus will concentrate its R&D investment on casdatifan, a potential best-in-class HIF-2α inhibitor.
Casdatifan targets a well-validated pathway and has demonstrated strong single-agent activity in more than 120 late-line clear cell renal cell carcinoma (ccRCC) patients enrolled in the ARC-20 Phase 1/1b study.
The data show improvement across all efficacy measures, including overall response rate and progression-free survival, versus results reported for the only approved HIF-2α inhibitor.
Arcus retains global rights to casdatifan outside Japan and parts of Asia, which were optioned to Taiho Pharmaceutical in October 2025.
The 2025 milestones for casdatifan are:
Early 2026: Additional ARC-20 monotherapy analyses in late-line ccRCC, including updated PFS for the 100 mg QD dose selected for Phase 3.
Mid-2026: More mature ARC-20 combination data for casdatifan + cabozantinib in IO-experienced patients, aligned with the ongoing Phase 3 PEAK-1 study.
Second Half 2026: Initial ARC-20 data in earlier-line settings and a go/no-go decision for the Phase 3 portion of eVOLVE-RCC02.
Late 2026: Potential initiation of a Phase 3 registrational trial in early- or first-line ccRCC.
Oncology Pipeline
Arcus is also advancing quemliclustat, a small-molecule CD73 inhibitor. The Phase 3 PRISM-1 trial in first-line metastatic pancreatic ductal adenocarcinoma completed enrollment earlier this year. Results are expected in 2027, evaluating quemliclustat plus gemcitabine/nab-paclitaxel versus the standard regimen.
I&I Pipeline
Arcus's immunology and inflammation portfolio includes several oral small-molecule programs targeting markets dominated by injectables.
Two candidates are expected to enter the clinic within the following timelines:
- 2026: MRGPRX2 for atopic dermatitis and chronic spontaneous urticaria.
- Late 2026–Early 2027: TNF inhibitor for rheumatoid arthritis, psoriasis and inflammatory bowel disease, including ulcerative colitis.
RCUS Price Action: RCUS stock is down 11.10% at $23.35 at publication on Friday.
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