BOT+BAL Shows Durable Survival in Refractory MSS Colorectal Cancer

Agenus Inc., developer of botensilimab (BOT) and balstilimab (BAL), reported mature Phase 1b results from its C-800-01 cohort in heavily pretreated patients with microsatellite-stable metastatic colorectal cancer. The study found a median overall survival of 21.2 months, significantly higher than the historical range of 10 to 14 months for comparable refractory patients.

The confirmed objective response rate reached 21%, including three complete responses and 23 partial responses. Notably, the treatment produced durable activity even in tumors with low tumor mutational burden (TMB) and no detectable PD-L1 expression.

Exploratory biomarker work showed that BOT+BAL activity was not confined to tumors carrying conventional biological markers linked with checkpoint sensitivity. The combination of botensilimab and balstilimab is designed to activate Fc-gamma receptors, promote T-cell priming, reduce regulatory T cells, and reshape the tumor environment.

Agenus plans to test BOT+BAL in a Phase 3 trial (ROBBIN) alongside neoadjuvant data from the NEST study. The company's stock traded at $7.67, down 1.79%, following the release of mature Phase 1b results.