Phase 1b Botensilimab (CTLA-4 mAb) & Balstilimab (PD-1 inhibitor) + SBRT in CRC

This pilot feasibility study by Massachusetts General Hospital evaluates a single‐arm combination treatment in chemorefractory, MSS (non-MSI-H/proficient mismatch repair) colorectal cancer with liver metastasis. Participants receive standard SBRT during cycle 1, followed by Botensilimab on Day 1 of 6-week cycles (cycles 1–4) and Balstilimab every 2 weeks (cycles 1–14) to assess safety and potential benefit in this challenging population; pMMR CRC is generally IO-resistant—SBRT priming plus dual checkpoint seeks durable control where chemo tails off.