STELLAR 303: Trial Design and Efficacy Outcomes of Zanzalintinib Plus Atezolizumab

Dr. Saeed presents the design and primary efficacy results of STELLAR 303, the phase 3 trial evaluating zanzalintinib plus atezolizumab versus regorafenib in patients with chemorefractory MSS metastatic colorectal cancer. With approximately 900 patients enrolled, STELLAR 303 is among the largest trials conducted in the third-line MSS colorectal cancer setting. The study used dual primary endpoints: overall survival in the intention-to-treat population and overall survival in patients without liver metastasis, with stratification by geographic region, RAS mutation status, and liver metastasis status. In the intention-to-treat population, median overall survival was approximately 11 months with zanzalintinib plus atezolizumab versus 9.4 months with regorafenib, representing a 20% reduction in the risk of death. Progression-free survival also favored the investigational arm at 3.7 versus 2.0 months. Dr. Saeed and Dr. Ahn discuss how these results apply across patient subgroups, including those with and without liver metastasis.