Agenus has reported new findings on MSS colorectal cancer through a peer-reviewed publication of mature Phase 1b results. The analysis evaluated BOT+BAL in heavily pre-treated patients.
The trial involved 123 patients with microsatellite stable metastatic colorectal cancer. There were no patients with active liver metastasis during the study. These results have been published in Clinical Cancer Research. Also, they have followed the results of three years’ effectiveness data from the ESMO GI Congress 2026.
The patients had undergone an average of three prior treatment regimens. In spite of their advanced condition, the BOT+BAL therapy provided a median overall survival period of 21.2 months. The three-year overall survival rate was 33%, while conventional later-line therapies typically provide an average survival of 10 to 14 months. The overall response rate was 21%, including three CRs and 23 PRs.
“These mature results are important because they show a pattern of durable activity in MSS colorectal cancer that is not limited to tumors with the conventional features associated with checkpoint sensitivity,” said Benjamin L. Schlechter, M.D., of Dana-Farber Cancer Institute and lead author of the publication. “In a heavily pretreated setting where patients have few remaining options, BOT+BAL compares favorably with what is typically expected from available later-line standard therapies in terms of tolerability, depth of response and duration of response. That is a meaningful clinical difference and provides important evidence that antitumor immunity can be generated even in tumors traditionally considered immunologically cold.”
BOT+BAL Shows Durable Responses in Heavily Treated Patients
Moreover, the median time to response had not yet been achieved. Responses persisted for at least 37.4 months. The rate of disease control was 69% at six weeks. The rate of clinical benefit was 28% at 24 weeks. At last follow-up, 17% of patients were alive and free of systemic anticancer therapy. These patients consisted of 13 responders. It is noteworthy that efficacy was demonstrated in the patients who were the most heavily pretreated. This subgroup consisted of 37 patients.
There was a 22% confirmed response rate with BOT+BAL in this cohort. Median overall survival was 16.2 months, whereas the three-year survival rate was 30%. There were also responses noted in tumors with low TMB. There were responses even in tumors without PD-L1 expression.
“BOT was specifically engineered to add Fc-mediated immune engagement to CTLA-4 blockade, with the goal of priming antitumor immunity in cancers that have historically been resistant to conventional checkpoint inhibition,” said Steven O’Day, M.D., Chief Medical Officer of Agenus. “This peer-reviewed publication connects the durable clinical activity observed in refractory MSS colorectal cancer with biomarker findings consistent with that biology. When considered alongside our emerging neoadjuvant data, these findings strengthen the rationale for evaluating BOT+BAL earlier in the disease course, where immune priming before surgery may offer the greatest opportunity to alter the trajectory of MSS colorectal cancer.”
Both markers failed to correlate with treatment response. Hence, these results reinforce the efficacy of the Fc-enhanced immune priming strategy employed by BOT. No safety signals were detected following long-term follow-up. In addition, there were no deaths from treatment-related causes.
Immune-mediated diarrhea and colitis were found to be resolved in 98% of affected patients. It took an average of 14 days for it to resolve. In conclusion, Agenus is planning to further evaluate the drug combination, BOT+BAL, in advanced stages of cancer. This will include the Phase 3 ROBBIN trial in MSS colon cancer.
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News Source: Businesswire.com
