Agenus announced clinical data from the MSS CRC (microsatellite stable colorectal cancer) 70 patient cohort of a Phase 1b study of botensilimab (multifunctional Fc-enhanced anti-CTLA-4) in combination with balstilimab (anti-PD-1) in patients with chemotherapy and/or immunotherapy-resistant tumors. The larger dataset continues to demonstrate that this combination offers superior efficacy and durability compared to what has been reported for standard of care and other investigational therapies in third line metastatic MSS CRC. The data were presented in the opening late-breaking oral session at the American Society of Clinical Oncology – Gastrointestinal Cancers Symposium (ASCO GI) in San Francisco, CA on Jan.

21 2023. Study Design and Highlights: A total of 70 evaluable patients with refractory metastatic MSS CRC received either 1 or 2 mg/kg botensilimab every 6 weeks and 3 mg/kg balstilimab every 2 weeks. Patient Demographics: Heavily pre-treated, with a median of 4 prior lines of therapy.

31% had received prior immunotherapy. Objective responses: 23% overall response rate. Other PD-(L)1 + CTLA-4 combinations in comparable patient populations have reported 1-5% response rates.

69% of objective responses were ongoing at data cut-off. 76% disease control rate (complete response + partial response + stable disease). Survival: 12-month overall survival of 63%.

Reported 12-month overall survival for standard of care is approximately 25%. Median overall survival has not been reached. Tolerability: Manageable gastrointestinal toxicity with a differentiated overall safety profile.

Presentation Details: Abstract Title: 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) (NCT03860272). Abstract Number: LBA8: Presenting Author:Anthony El-Khoueiry, MD, Phase I Program Director at the USC Norris Comprehensive Cancer Center, Keck Medicine of USC.