Extended Follow-up of Botensilimab plus Balstilimab in an Expanded Cohort of Microsatellite-Stable Metastatic Colorectal Cancer without Active Liver Metastases.

Botensilimab plus balstilimab produced an objective response rate of 21% in 123 patients with microsatellite-stable metastatic colorectal cancer without active liver metastases, with 36-month OS of 33%.

• Why it matters: MSS mCRC has limited options and responds poorly to conventional immunotherapy, especially in patients lacking active liver metastases. Extended follow-up is needed to clarify durability, survival, and safety.
• What they did: In a phase Ib cohort, patients received botensilimab 1 or 2 mg/kg every 6 weeks plus balstilimab 3 mg/kg every 2 weeks up to 2 years or until progression/toxicity; safety was primary and ORR, DOR, PFS, and exploratory OS were assessed. Post hoc analyses evaluated late-line exposed patients (n = 37).
• The result: Median DOR was not reached (95% CI, 7.3-NR), median PFS was 4.0 months, and median OS was 21.2 months (36-month OS, 33%; 95% CI, 24-43), with manageable treatment-related diarrhea (39%) and fatigue (37%). In late-line exposed patients, ORR was 22% and median OS was 16.2 months, supporting further evaluation.

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