Agenus announces Phase 1b data of botensilimab in combo with balstilimab

Agenus announced expanded data from the company’s phase 1b study of botensilimab in combination with balstilimab in patients with advanced sarcomas. The results were presented in an oral presentation at the European Society for Medical Oncology Congress 2023. “These results reinforce the promising potential of BOT+BAL in multiple cold, treatment-resistant solid tumors,” said Steven O’Day, Chief Medical Officer. “Notably, we observed several durable responses extending past one year, including patients with visceral angiosarcoma, which is traditionally unresponsive to immunotherapy, as well as other cold subtypes like leiomyosarcoma. As we expand the study, we aim to focus on key subsets and dosing strategies to maximize benefit for patients.” “As the study has advanced, BOT+BAL continues to demonstrate encouraging results in a larger population of patients with difficult to treat sarcomas, with a median response duration of 19.4 months and a 40% 6-month progression-free survival rate. We’re also seeing a dose-dependent effect, with a 29% objective response rate at 2 mg/kg,” said Breelyn Wilky, Director of Sarcoma Medical Oncology at the University of Colorado, and study investigator. A total of 41 evaluable patients received either 1 or 2 mg/kg BOT every 6 weeks and 3 mg/kg BAL every 2 weeks. Majority of patients had either angiosarcoma or leiomyosarcoma subtypes. Patients were heavily pre-treated, with a median of three prior lines of therapy, including 16% who received prior PD-(L)1 therapy. Majority of patients had biomarkers associated with poor response to immunotherapy: 87% had a low tumor mutation burden, 74% of patients were PD-L1 negative by immunohistochemistry. No new safety signals reported, with tolerability consistent across tumor types. Adverse events were generally manageable and reversible. Diarrhea/colitis was the most clinically significant immune-mediated adverse event. No grade 4 or 5 treatment-related adverse events and no related cases of irreversible events such as hypophysitis, pneumonitis, hepatitis, or myocarditis were reported.