Agenus reports response rate in colon cancer trial

Agenus (AGEN) reported that 72% of patients with locally advanced colon cancer had no detectable cancer remaining at surgery after receiving a six-week course of its experimental immunotherapy combination, according to phase 2 clinical trial results presented at the European Society for Medical Oncology's 2026 congress in Madrid.

The NEOASIS study, conducted by the Netherlands Cancer Institute, evaluated Agenus' botensilimab and balstilimab in 18 patients with mismatch repair-deficient colon cancer. This form of cancer has a genetic defect that prevents cells from properly repairing DNA damage, making tumors potentially more vulnerable to treatments that stimulate the immune system.

The study met its primary goal, with 83% of patients achieving a major pathologic response, meaning 10% or less of their tumor remained alive when examined after surgery. Thirteen patients, or 72%, achieved a complete pathologic response, with no cancer detected in the removed tumor or nearby lymph nodes. All patients had advanced disease, including 67% whose tumors had grown through the bowel wall and 72% whose cancer had spread to nearby lymph nodes.

For investors, the findings strengthen the case for Agenus' (AGEN) experimental immunotherapy combination as a potential treatment before surgery, possibly reducing the need for prolonged chemotherapy or more extensive operations. However, the study involved only 18 patients, lacked a comparison group and remains too preliminary to establish whether the treatment improves long-term survival or prevents recurrence.

At a median follow-up of 15 months, all 18 patients were alive and 16 remained free of cancer recurrence. Side effects were generally mild or moderate, although one patient developed severe inflammation of the colon that resolved with treatment. All patients underwent surgery, including one whose operation was moved forward because of a bowel obstruction.

Botensilimab and balstilimab are designed to help the immune system attack cancer by blocking two proteins, CTLA-4 and PD-1, that ordinarily restrain immune activity. Researchers are now enrolling patients with dMMR rectal cancer to investigate whether the combination could eliminate tumors sufficiently to allow some patients to avoid surgery.

Agenus (AGEN) is also developing the treatment approach for microsatellite-stable colon cancer, a more common form of the disease that is generally less responsive to immunotherapy. Both drugs remain investigational and aren't approved by the U.S. Food and Drug Administration.