Agenus has announced that new long-term data evaluating botensilimab plus balstilimab (BOT+BAL) in patients with recurrent ovarian cancer will be presented at the International Gynecologic Cancer Society (IGCS) 2026 Annual Global Meeting, taking place October 1–3, 2026, in Montréal, Canada.
The upcoming presentation will report results from the recurrent ovarian cancer cohort of the C-800-01 study (NCT03860272), including patients with platinum-resistant and platinum-refractory disease. According to Agenus, the analysis will include outcomes according to platinum sensitivity status as well as three-year overall survival (OS).
Importantly, Agenus has not yet disclosed the numerical three-year OS results. The updated survival data are scheduled to be presented at IGCS 2026.
Three-Year Follow-Up to Extend Earlier BOT+BAL Findings
The IGCS presentation will provide longer-term follow-up of a BOT+BAL ovarian cancer cohort for which clinical results were previously published in the Journal for ImmunoTherapy of Cancer in December 2025.
In the earlier analysis, 44 patients with treatment-refractory ovarian cancer were evaluable for safety, and 35 patients were evaluable for efficacy. Patients had received a median of three previous lines of therapy, representing a heavily pretreated population with limited remaining treatment options.
BOT+BAL produced a confirmed objective response rate (ORR) of 23%, with responses reported in 8 of 35 efficacy-evaluable patients. These included one complete response and seven partial responses.
The disease control rate was 60%, while the clinical benefit rate, defined as complete response, partial response, or stable disease lasting at least 24 weeks, was 31%.
Among responding patients, the median duration of response was 9.7 months. Median progression-free survival was 2.8 months, while median overall survival reached 14.8 months. The estimated 12-month overall survival rate was 75% and the previously reported 18-month OS rate was 50%.
The new IGCS analysis is therefore expected to provide a substantially more mature assessment of survival, extending observation to the three-year landmark and examining outcomes according to platinum sensitivity.
Botensilimab + Balstilimab in Platinum-Resistant Ovarian Cancer
Focus on Platinum-Resistant and Platinum-Refractory Ovarian Cancer
Platinum resistance remains a major therapeutic challenge in recurrent ovarian cancer. The population included in the previous BOT+BAL analysis was particularly difficult to treat, with nearly three-quarters of participants having platinum-resistant or platinum-refractory disease.
Earlier studies of conventional immune checkpoint inhibition have generally demonstrated limited activity in recurrent ovarian cancer, contributing to interest in strategies designed to generate stronger antitumor immune responses in tumors that have historically been relatively resistant to checkpoint blockade.
Responses with BOT+BAL in the previously published C-800-01 cohort were observed across several ovarian cancer histologies, including high-grade serous, clear cell and endometrioid tumors.
The upcoming analysis by platinum sensitivity status could therefore provide additional information on whether long-term outcomes differ across clinically important ovarian cancer subgroups.
What Is Botensilimab Plus Balstilimab?
Botensilimab is an investigational Fc-enhanced multifunctional anti-CTLA-4 antibody developed by Agenus. The antibody is designed to stimulate both innate and adaptive antitumor immune responses, including through T-cell priming and activation, modulation of intratumoral regulatory T cells and activation of myeloid cells.
Balstilimab is an investigational fully human IgG4 monoclonal antibody targeting PD-1 and designed to inhibit interaction of PD-1 with its ligands PD-L1 and PD-L2.
The combination is being investigated as an approach to expand the effectiveness of immune checkpoint therapy into tumors that have historically demonstrated limited responsiveness to conventional PD-1 and CTLA-4 inhibition. Agenus reported in September 2026 that approximately 1,300 patients had been treated with botensilimab and/or balstilimab across Phase 1 and Phase 2 studies.
Safety Findings From the Earlier Ovarian Cancer Analysis
In the previously published ovarian cancer cohort, the most frequent treatment-related adverse event was diarrhea/colitis, occurring in 43% of patients, with grade 3 events reported in 16%.
No treatment-related deaths were reported. The investigators described immune-mediated toxicities as manageable and reversible with established interventions, including corticosteroids and, when appropriate, tumor necrosis factor-alpha inhibitors.
Longer follow-up at IGCS may provide further perspective on the durability of clinical benefit, although Agenus’ September 10 announcement specifically emphasized survival and analyses according to platinum sensitivity status rather than announcing new safety findings.
About the C-800-01 Trial
C-800-01 (NCT03860272) is a multicohort clinical study evaluating botensilimab alone and in combination with balstilimab in patients with advanced solid tumors.
The study includes patients with several malignancies, including ovarian cancer, colorectal cancer, non-small cell lung cancer, endometrial cancer, prostate cancer and other advanced solid tumors. The ClinicalTrials.gov record lists 499 participants enrolled in the overall study.
The ovarian cancer cohort has been reported as a Phase 1b evaluation of BOT+BAL. Earlier efficacy endpoints included objective response rate, duration of response, disease control, clinical benefit, progression-free survival and overall survival.
BOT+BAL Presentation at IGCS 2026
The abstract is titled “Next Generation Immune Checkpoint Inhibition with Botensilimab Plus Balstilimab in Recurrent Ovarian Cancer: Results by Platinum Sensitivity Status and 3-Year Overall Survival.”
The research will be presented by Rebecca L. Porter, MD, of Dana-Farber Cancer Institute, as Poster Presentation 969 during the “Poster Rounds with Professors Session, Ovarian Cancer 03.”
The presentation is scheduled for October 3, 2026, from 10:50 to 10:55 AM EDT at the IGCS Annual Global Meeting in Montréal.
The IGCS 2026 Annual Global Meeting, organized by the International Gynecologic Cancer Society, will take place October 1–3 at the Palais des Congrès de Montréal and will bring together specialists across gynecologic oncology to present new clinical research and developments in the management of gynecologic cancers.
The forthcoming three-year survival analysis will provide important additional follow-up for BOT+BAL in recurrent ovarian cancer and may help clarify the durability of benefit observed in the earlier Phase 1b dataset, particularly among patients with platinum-resistant or platinum-refractory disease.
Read further on OncoDaily: Agenus Announces Up to $340M Financing to Advance Phase 3 ROBBIN of Neoadjuvant BOT/BAL in MSS Colon Cancer
