Multicenter phase 1 trial of botensilimab plus balstilimab in patients with relapsed or refractory metastatic sarcomas

There is a high unmet need to develop novel therapies for patients with advanced sarcomas. A multicenter phase 1 trial in the United States evaluated the combination of botensilimab (BOT; Fc-enhanced anti-CTLA-4 antibody) and balstilimab (BAL; anti-PD-1 antibody) for relapsed or refractory metastatic sarcomas. The most-common treatment-related adverse event was diarrhea/colitis occurring in 35.9% of patients, with grade 3 in 6.3% of patients. No grade 4 or 5 TRAEs were reported. Among evaluable patients, the objective response rate was 19.2% (95% CI 9.6-32.5) for all patients and 27.8% (9.7-53.5) for patients with angiosarcoma. The median follow-up was 9.1 months. Median progression-free survival and overall survival were 4.4 months (95% CI 2.8-6.1) and not reached (14.0-NR), respectively. The authors conclude that the combination of BOT and BAL demonstrated promising efficacy and safety in a large cohort of pretreated metastatic sarcoma patients.