PRIMARY OBJECTIVES:~I. To identify the recommended phase 2 dose (RP2D) of botensilimab, balstilimab, and regorafenib (BBR) in patients with chemotherapy-resistant microsatellite stable (MSS) metastatic colorectal cancer (MSS mCRC). (Phase I) II. To estimate the overall response rate (ORR) of botensilimab, balstilimab, and regorafenib in patients with chemotherapy-resistant MSS mCRC, with and without liver metastatic disease. (Phase II)~SECONDARY OBJECTIVES:~I. Describe the safety of botensilimab, balstilimab, and regorafenib at all evaluable dose levels. (Phase I) II. Describe the efficacy of BBR in terms of ORR, progression free survival (PFS) and overall survival (OS). (Phase I) III. To evaluate the safety/feasibility of botensilimab, balstilimab, and regorafenib through the assessment of adverse events. (Phase II) IV. Estimate the PFS, OS and duration of response (DOR). (Phase II)~CORRELATIVE OBJECTIVES:~I. Evaluate potential circulating biomarkers of response, resistance, activity, and toxicity. (Phase I/II) II. Correlate baseline molecular biomarkers (RAS, BRAF, TMB, and PD-L1 if available), with overall outcome. (Phase I/II)~OUTLINE: This is a phase I, dose-escalation study of botensilimab followed by a phase II study.~Patients receive botensilimab intravenously (IV), balstilimab IV, and regorafenib orally (PO) on study. Patients also undergo computed tomography (CT) and collection of blood throughout the study.
This phase I/II trial tests how well botensilimab, balstilimab, and regorafenib works in treating patients with microsatellite stable colorectal cancer that has spread from where it first started (primary site) to other places in the body (metastatic) or that may have spread from where it first started to nearby tissue, lymph nodes, or distant parts of the body (advanced) and who have progressed on prior chemotherapy. Immunotherapy with monoclonal antibodies, such as botensilimab and balstilimab, may help the body's immune system attack the cancer, and may interfere with the ability of tumor cells to grow and spread. Regorafenib binds to and inhibits growth factor receptors, which may inhibit the growth of new blood vessels that tumors need to grow. Giving botensilimab, balstilimab, and regorafenib in combination may work better in treating patients with metastatic colorectal cancer than giving these drugs alone.