Lexington, Mass. — Agenus reported three-year follow-up data showing an estimated 48% overall survival rate among evaluable patients with recurrent ovarian cancer treated with its experimental immunotherapy combination botensilimab and balstilimab.
The results from the ovarian cancer cohort of the company’s Phase 1b C-800-01 trial were presented at the 2026 International Gynecologic Cancer Society Annual Global Meeting in Montréal.
Botensilimab, or BOT, is an Fc-enhanced anti-CTLA-4 antibody, while balstilimab, or BAL, is an anti-PD-1 antibody.
Among 35 patients evaluable for efficacy, estimated overall survival was 48% at both two and three years, with median overall survival of 14.8 months.
The objective response rate was 23%, including one complete response and seven partial responses. Median duration of response was 9.7 months, while 31% of patients achieved a response or stable disease lasting at least 24 weeks.
At the latest follow-up, 11 of the 44 patients who received at least one dose of treatment were alive and no longer receiving therapy.
Patients in the study had received a median of four prior lines of therapy. Nearly three-quarters had platinum-resistant or refractory disease, while 77% had previously received bevacizumab and 57% had received a PARP inhibitor.
“What stands out with longer follow-up is the survival plateau in patients who had already received multiple treatments,” said Rebecca L. Porter, M.D., of Dana-Farber Cancer Institute, who presented the data.
Among 25 patients with platinum-resistant or refractory disease, estimated three-year survival was 47% and the objective response rate was 20%.
For 10 patients with platinum-sensitive disease, estimated three-year survival was 45%, with three patients achieving partial responses.
Among patients who had received at least four previous lines of therapy, estimated three-year survival was 48%. In 17 patients whose disease had progressed during PARP inhibitor treatment or maintenance, estimated three-year survival was 61%.
Agenus said the safety results remained consistent with the known profile of the BOT+BAL combination, with no new safety signals or treatment-related deaths reported.
“The most compelling finding is that the survival curve extends beyond two years in women who had already received multiple treatments,” said Steven J. O’Day, M.D., Chief Medical Officer of Agenus.
The company said the ovarian cancer results add to evidence of long-term survival observed with BOT+BAL in other difficult-to-treat cancers and support continued evaluation of the combination earlier in the course of disease.
