Agenus Inc. (Nasdaq: AGEN) presented three-year follow-up data from a Phase 1b clinical trial evaluating the combination of botensilimab (BOT) and balstilimab (BAL) in patients with refractory microsatellite-stable metastatic colorectal cancer without active liver metastases, according to a company statement.

The data were presented at the European Society for Medical Oncology Gastrointestinal Cancers Congress 2026 on July 2 in Munich, Germany.

The fully enrolled 123-patient cohort showed a median overall survival of 21.2 months, a 36-month overall survival rate of 33%, and a 24-month overall survival rate of 41%. The Kaplan-Meier survival curve showed a plateau beyond two years. Available later-line standards in this patient population have historically reported median overall survival of approximately 10 to 14 months.

The confirmed objective response rate was 21%, including three complete responses and 23 partial responses. Median duration of response was not reached, with responses ranging from 1.9 months to at least 37.4 months. The disease control rate was 69% at six weeks, and the clinical benefit rate was 28% at 24 weeks. Tumor regression was observed in more than 40% of patients.

At last follow-up, 21 patients, or 17%, were alive and off all systemic anticancer therapy, including 13 responders.

Patients had received a median of three prior lines of therapy, and 67% had received at least three prior lines.

Extended safety follow-up showed no new safety signals and no treatment-related deaths. Immune-mediated diarrhea and colitis, the most common immune-mediated adverse event, resolved in 98% of affected patients, with a median time to resolution of 14 days. The BOT 1 mg/kg plus BAL regimen showed lower rates of immune-mediated diarrhea and colitis compared with the 2 mg/kg regimen.

Agenus said the findings support the ongoing randomized Phase 3 BATTMAN trial evaluating BOT plus BAL in refractory MSS metastatic colorectal cancer.