Next Steps for Evaluating Balstilimab Plus Botensilimab in MSS mCRC

Marwan G. Fakih, MD, professor in the Department of Medical Oncology & Therapeutics Research, co-directs the Gastrointestinal Cancer Program at City of Hope Comprehensive Cancer Center, discusses the next steps for the clinical development of the combination of balstilimab with botensilimab for the treatment of patients with microsatellite stable (MSS) metastatic colorectal cancer (mCRC) without liver metastases.

This combination is currently being evaluated in the phase 2 trial (NCT05608044). Findings were presented at the 2025 Gastrointestinal Cancers Symposium.

Transcription:

0:10 | The next step is to have a confirmatory trial to prove that this combination is better than best supportive care. Of interest is the fact that we did have a control arm in the study that we reported on, and that was the standard arm of trifluridine or regorafenib, but only 21 patients enrolled in that arm, and partly because some patients who were randomized to this arm actually dropped off before receiving treatment. In the 21 patients who received trifluridine in our trial, there were no responses. As expected, the response rate for trifluridine as monotherapy is historically about 2% to 3%, and regorafenib is only a 1% response rate, so those agents do not really result in major shrinkage.

1:08 | We do believe that if we go to a phase 3 clinical trial, it will hopefully be positive, but it will be required by regulatory bodies, and the goal is to proceed with a randomized phase 3 clinical trial with an overall survival end point to confirm beyond doubt the benefits that we see in our phase 2.

REFERENCE:

Fakih M, Segal NH, Schlechter BL, et al. Preliminary results from a randomized, open-label, phase 2 study of botensilimab (BOT) with or without balstilimab (BAL) in refractory microsatellite stable metastatic colorectal cancer with no liver metastases (MSS mCRC NLM). J Clin Oncol. 2025;43(suppl 4):23. doi:10.1200/JCO.2025.43.4_suppl.23