Botensilimab plus balstilimab showed encouraging long-term results in patients with heavily pretreated microsatellite-stable (MSS) metastatic colorectal cancer without active liver metastases, according to three-year follow-up from the phase 1b C-800-01 trial.
Among 123 patients, median overall survival reached 21.2 months, nearly double the historical 10–14 months seen with standard later-line treatments. The objective response rate was 21%, including three complete responses, while 33% of patients were still alive at three years. Notably, 17% remained alive without needing systemic cancer treatment, with some treatment-free for more than two years.
The combination also benefited patients whose disease had progressed after newer therapies such as regorafenib and fruquintinib. No new safety concerns or treatment-related deaths were reported. The most common side effect was immune-related diarrhea or colitis, which was generally manageable. The regimen is now being tested against best supportive care in the ongoing phase 3 BATTMAN trial.