For patients with heavily pretreated microsatellite stable colorectal cancer, botensilimab plus balstilimab demonstrates promising clinical activity with durable responses and a well-tolerated safety profile.

Results from this study were presented on Saturday, January 21, 2023, at the American Society of Clinical Oncologists Gastrointestinal Cancers Symposium in San Francisco, CA, by Anthony El-Khoueiry, MD, Norris Comprehensive Cancer Center at University of Southern California, Los Angeles, CA.

In this study, 59 patients with metastatic microsatellite stable colorectal cancer were evaluable at the time of reporting. Patients received either 1 or 2 mg/kg botensilimab every 6 weeks or botensilimab plus 3 mg/kg balstilimab every 2 weeks. Crossover from monotherapy to combination therapy was permitted as rescue therapy.

At a median follow-up duration of 6.4 months, the objective response rate (ORR) of all patients was 22% and the disease control rate (DCR) was 73%. The median duration of response was not reached, with 9 of the 13 responses ongoing. The 12-month overall survival rate was 61% with the median overall survival not reached. Patients who received 1 mg/kg of botensilimab (n = 8) had an ORR of 38% and a DCR of 100%, while patients who received 2 mg/kg (n = 50) had an ORR of 20% and a DCR of 70%.

There were 32% of patients who experienced a grade 3 treatment related-adverse event, and 2% who experienced a grade 4. The only grade 3/4 treatment-related adverse event that occurred in more than 3 patients was diarrhea/colitis. No grade 5 treatment-related adverse events were reported. In 15% of patients a treatment-related adverse event led to discontinuation of botensilimab alone, and in 12% it led to discontinuation of both botensilimab and balstilimab.

Dr El-Khoueiry et al concluded “In heavily pretreated metastatic [microsatellite stable colorectal cancer] patients, [botensilimab plus balstilimab] continues to demonstrate promising clinical activity with durable responses and was well-tolerated with no new immune-mediated safety signals.

Source:

El-Khoueiry A, Fakih M, Gordon MS, et al. Results from a phase 1a/1b study of botensilimab (BOT), a novel innate/adaptive immune activator, plus balstilimab (BAL; anti-PD-1 antibody) in metastatic heavily pretreated microsatellite stable colorectal cancer (MSS CRC). Presented at 2023 ASCO Gastrointestinal Cancers Symposium; January 19-21, 2023; San Francisco, CA. Abstract LBA8