Multicenter randomized phase 2 study of addition of CMB305 to atezolizumab for synovial sarcoma or myxoid liposarcoma

CMB305 is a prime-boost vaccine regimen that targets the NY-ESO-1 antigen. Synovial sarcoma and myxoid lipsarcoma are soft-tissue sarcomas with high frequeny of NY-ESO-1 expression. A multicenter randomized phase 2 study evaluated addition of CMB305 to atezolizumab for advanced synovial sarcoma or myxoid liposarcoma. The median PFS was 2.6 months in the CMB305-atezolizumab arm versus 1.6 months in de atezolizumab monotherapy arm (HR 0.9; 95% CI 0.6-1.3) and the median OS was 18 months in both arms. Post-hoc analysis among dosed patiënt showed that patients developing a T-cell response had longer median OS (36 months) compared to patients without T-cell response (HR 0.3; p=0.02). The authors conclude that combining prime-boost vaccines with anti-PD-L1 therapies merits furtherevaluation in other clinical contexts.