Agenus Announces Peer-Reviewed Publication Linking BOT+BAL’s Durable Survival in MSS Metastatic Colorectal Cancer to Its Distinct Immune-Priming Mechanism
Mature 123 patient analysis reports 21.2-month median overall survival and 33% three-year overall survival in heavily pretreated MSS mCRC without active liver metastases
Responses observed in tumors with low tumor mutational burden and no PD-L1 expression, reinforcing BOT's Fc-enhanced immune priming mechanism in immunologically "cold" tumors
Durable clinical activity and biomarker findings add biological rationale for evaluating BOT+BAL earlier in the disease course, including curative-intent neoadjuvant colon cancer
LEXINGTON, Mass., August 28, 2026--Agenus Inc. (Nasdaq: AGEN), a leader in immuno-oncology innovation, today announced the peer-reviewed publication of mature Phase 1b results from the fully enrolled C-800-01 cohort evaluating botensilimab (BOT), a multifunctional Fc-enhanced anti–CTLA-4 antibody, plus balstilimab (BAL), an anti–PD-1 antibody, in 123 heavily pre-treated patients with microsatellite-stable (MSS) metastatic colorectal cancer (mCRC) without active liver metastases.
The manuscript, titled "Extended Follow-Up of Botensilimab Plus Balstilimab in an Expanded Cohort of Microsatellite-Stable Metastatic Colorectal Cancer Without Active Liver Metastases," was published in Clinical Cancer Research. The publication builds on three-year efficacy data presented at the European Society for Medical Oncology Gastrointestinal Cancers (ESMO GI) Congress 2026 and provides additional biomarker analyses offering insight into the biology underlying BOT+BAL activity.
MSS tumors account for the vast majority of mCRC cases and have historically derived little or no benefit from conventional checkpoint immunotherapy. In this fully enrolled cohort, patients received a median of three prior lines of therapy. BOT+BAL demonstrated a median overall survival of 21.2 months and a three-year overall survival rate of 33%. In this treatment setting, available later-line standard treatments have reported median overall survival of approximately 10-14 months in patients with refractory MSS, without active liver metastases.i
Durable clinical activity was observed in the context of limited drug exposure, with patients receiving a median of two BOT doses and six BAL doses. In exploratory analyses, responses were observed in tumors lacking the conventional markers of checkpoint sensitivity including low tumor mutational burden (TMB) and no detectable PD-L1 expression, and neither biomarker was associated with response. These findings are consistent with BOT's Fc-enhanced design, intended role in promoting immune priming in immunologically "cold" tumors.