Exelixis (EXEL) Zanzalintinib Trial Fails Primary Endpoint in Lung Cancer

Exelixis Inc. (EXEL) announced on June 22, 2026, that its Phase 3 STELLAR-303 trial for zanzalintinib in combination with atezolizumab did not meet its primary endpoint of progression-free survival (PFS). The study evaluated the combination in previously treated metastatic non-small cell lung cancer (NSCLC) patients with actionable mutations. The trial also did not demonstrate a clear benefit in key secondary endpoints, including overall survival (OS) and objective response rate (ORR). Despite the lack of efficacy, the zanzalintinib and atezolizumab combination was generally well-tolerated, consistent with the known safety profiles of both agents. Exelixis stated it will continue to analyze the full dataset to determine future development plans for zanzalintinib in this indication.