Agenus reports data from Phase 1b trial of botensilimab/balstilimab combination

Agenus shared data from its Phase 1b trial on the botensilimab and balstilimab combination at a late-breaking session at the 2023 ESMO World Congress on Gastrointestinal Cancer. The new data show substantial survival benefits and long-lasting responses for patients with non-MSI-H metastatic colorectal cancer previously resistant to chemotherapy and/or immunotherapy. Agenus is planning to submit its first Biologics License Application to the U.S. Food & Drug Administration for patients with non-MSI-H metastatic colorectal cancer. The ongoing global randomized phase 2 trial for patients with non-active liver metastases has been granted Fast Track Designation from the FDA. Additionally, global randomized Phase 2 trials for the botensilimab/balstilimab combination in melanoma and botensilimab/chemotherapy in pancreatic cancer are underway, with plans to initiate Phase 3 studies in colorectal and non-small cell lung cancer. The study enrolled 101 patients with refractory non-MSI-H metastatic colorectal cancer who were administered botensilimab and balstilimab. The patients had a median of four prior therapy lines, with 25% having failed previous immunotherapy. Efficacy was evaluated in 87 patients who had undergone at least one six-week post-baseline imaging scan. Of these, 69 patients had no active liver metastases, defined as patients with no history of liver metastases or those with metastases that were treated or ablated without recurrence. Half of the patients treated had poor-prognostic metastatic sites beyond the liver, such as bone and soft tissue. Patients without active liver metastases had a 12-month overall survival (OS) estimate of 74% and a median overall survival of 20.9 months, surpassing the recently reported 12.9-month benchmark with standard of care. Patients with active liver metastases had a 12-month OS estimate of 30% and a mOS of 8.7 months, surpassing the recently reported 5.9-month benchmark with standard of care. The botensilimab/balstilimab combination showed a survival benefit, regardless of RECIST 1.1 responses. mOS estimates for patients, categorized by liver status, were comparable between the efficacy evaluable and the intent-to-treat populations. Evaluable patients without active liver metastases showed a confirmed objective response rate of 23% and a disease control rate of 80%, significantly higher than the reported response rate of 3% with standard of care. The responses were durable, with 69% of objective responses ongoing at data cutoff. Response durations ranged from 1.4+ months in recently treated patients to over 24.3+ months. The botensilimab/balstilimab combination demonstrated a manageable safety profile, with no new safety concerns emerging.