The biotechnology firm Agenus disclosed pivotal data for its BOT/BAL combination therapy in treating refractory MSS metastatic colorectal cancer at the 2026 European Society for Medical Oncology Gastrointestinal Cancers Congress today. The research indicates a three-year overall survival rate of 33% in the patient subgroup without active liver metastases.
This study evaluated the efficacy and safety of the combined use of botensilimab and balstilimab in patients with MSS-type metastatic colorectal cancer who had previously received standard treatments. MSS-type colorectal cancer accounts for approximately 95% of all colorectal cancer cases. These tumors typically respond poorly to existing immune checkpoint inhibitor monotherapies, representing a significant unmet medical need. The BOT/BAL combination is a novel immunotherapy approach designed to synergistically activate anti-tumor immune responses through dual targeting of CTLA-4 and PD-1.
Data presented at ESMO GI 2026 shows that in the patient subgroup without active liver metastases, the BOT/BAL treatment group achieved a three-year overall survival rate of 33%, significantly higher than historical control data. In the subgroup with liver metastases, the overall survival period was 8.1 months, which also outperformed historical controls. Furthermore, sustained and durable tumor responses were observed in both dosage groups.
A research lead at Agenus stated that these findings suggest BOT/BAL has the potential to transform the treatment landscape for MSS-type colorectal cancer. Notably, for patients without active liver metastases, over one-third survived for three years post-treatment, representing a breakthrough for a patient population historically associated with a very poor prognosis.
Globally, there are approximately 1.9 million new cases of colorectal cancer each year, with about one-quarter being metastatic patients. The MSS-type constitutes the majority of metastatic colorectal cancer cases, typically associated with a five-year survival rate of less than 15%.
The safety profile was consistent with previous reports. The most common treatment-related adverse events were fatigue, diarrhea, and rash, with no new safety signals observed.
Agenus indicated that, based on this data, the company plans to engage with regulatory authorities to advance the registration and approval process for the BOT/BAL combination for this indication. The company is concurrently conducting multiple clinical trials targeting other MSS-type tumors to explore the broader application potential of this combination therapy.
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