Exelixis today announced detailed results from its Phase 3 STELLAR‑303 trial, a global, multicenter, randomized, open‑label study evaluating zanzalintinib plus atezolizumab versus regorafenib in patients with previously treated non‑MSI‑high metastatic colorectal cancer. The trial enrolled 901 patients (451 in the combination arm and 450 in the control arm) and met one of its dual primary endpoints, demonstrating a 20% reduction in the risk of death (hazard ratio 0.80, 95% CI 0.69‑0.93, P = 0.0045). Median overall survival was 10.9 months for the combination versus 9.4 months for regorafenib, with a 12‑month landmark OS estimate of 46% versus 38%.
Progression‑free survival also trended in favor of the combination, with a stratified hazard ratio of 0.68 (95% CI 0.59‑0.79) and median PFS of 3.7 months versus 2.0 months. Safety data were consistent with prior studies; grade 3/4 treatment‑related adverse events occurred in 59% of patients receiving the combination compared with 37% on regorafenib, and discontinuation due to adverse events was 18% versus 15%. The most common grade 3/4 events were hypertension, fatigue, diarrhea, and proteinuria.
These results represent the first immunotherapy‑based Phase 3 trial to demonstrate a statistically significant overall‑survival benefit with a differentiated kinase inhibitor versus standard of care in metastatic colorectal cancer, underscoring the therapeutic potential of zanzalintinib in this setting. Exelixis indicated that it intends to file a new drug application for the combination in the United States before the end of 2025, positioning the company to pursue regulatory approval and market entry in a high‑need indication.
The STELLAR‑303 trial was presented at the 2025 European Society for Medical Oncology Congress and simultaneously published in The Lancet, providing peer‑reviewed evidence of the combination’s efficacy and safety profile. With a global enrollment of 901 patients and a robust follow‑up of 18 months, the data support the continued development of zanzalintinib as a potential new standard for patients with previously treated metastatic colorectal cancer.
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