Agenus shared on LinkedIn:
“At Society for Immunotherapy of Cancer (SITC)’s SITC 2026, a long-term survivor analysis of botensilimab + balstilimab (BOT+BAL) in refractory MSS metastatic colorectal cancer will be presented.
The analysis shows that long-term survival was not limited to patients with favorable baseline characteristics. Some long-term survivors remain alive and off all anticancer therapy, and patients with fewer prior lines of treatment were more likely to achieve long-term survival.
These results support our Phase 3 ROBBIN strategy of evaluating BOT+BAL earlier in treatment.
SITC 2026 Presentation Details
- Title: Clinical Features of Long-Term Survivors Treated with Next-Generation Anti–CTLA-4 (Botensilimab) Plus Anti–PD-1 (Balstilimab) in Refractory Microsatellite-Stable Metastatic Colorectal Cancer
- Presenter: Thomas U. Marron, MD, PhD; Tisch Cancer Center at Mount Sinai, New York, NY
- Date: Saturday, November 7, 2026
- Time: 10:00 a.m.–2:00 p.m. and 6:00–8:10 p.m. MST | 12:00–4:00 p.m. and 8:00–10:10 p.m. EST
- Location: North Building, Lower Level, Exhibition Halls 4–5–6, Phoenix, Arizona
- Poster Number: 472
Press Release Details
According to the presentation detailed by Dr. Thomas U. Marron from the Tisch Cancer Center at Mount Sinai, a post hoc analysis of the phase 1b study (C-800-01) focused on patients who achieved long-term survival. More than half of the evaluable patients in the cohort – specifically 51% (63 out of 123 patients without active liver metastases) – achieved long-term survival, defined as surviving for at least 18 months following the initiation of the BOT+BAL regimen.
Among these long-term survivors, the objective response rate was 35%, which included three complete responses, and the median duration of response was not yet reached, with individual responses lasting anywhere from 1.9 months to over 37.4 months. A notable finding from the analysis was that approximately 1 in 4 of these long-term survivors (24%) were alive and completely off all systemic cancer therapy at their last follow-up.
The data also revealed a correlation between prior treatment history and long-term survival outcomes. Patients who achieved long-term survival had received fewer prior lines of therapy compared to shorter-term survivors (56% versus 78% having received three or more prior regimens), providing strong rationale for evaluating this immunotherapy combination earlier in the treatment course.
This strategy forms the foundation of Agenus’s ongoing and planned clinical developments, including the Phase 3 ROBBIN trial, which aims to evaluate botensilimab and balstilimab in earlier settings, such as pre-surgery for high-risk MSS colon cancer.
Regarding safety, no treatment-related deaths were reported in the analysis. While immune-mediated adverse events – most notably immune-mediated diarrhea or colitis – occurred and were managed with standard protocols like early corticosteroids and targeted therapies, 97% of affected long-term survivors experienced resolution.
Company leadership emphasized that these durable responses in traditionally immunotherapy-resistant ‘cold’ tumors highlight the potential of botensilimab’s Fc-enhanced immune-priming mechanism.
You can also read: Agenus Reports 51% 18-Month Survival With BOT+BAL in MSS Colorectal Cancer
