Patients eligible for the epithelioid sarcoma cohort (cohort 5) were aged 16 years or older with histologically confirmed, locally advanced or metastatic epithelioid sarcoma; documented loss of INI1 expression by immunohistochemical analysis or biallelic SMARCB1 (the gene that encodes INI1) alterations, or both;...16 (26% [95% CI 16–39]) patients had disease control at 32 weeks. Median time to response was 3·9 months (IQR 1·9–7·4). Median progression-free survival was 5·5 months (95% CI 3·4–5·9), and median overall survival was 19·0 months (11·0–not estimable).

This was a phase 2, multicenter, open-label, single arm study of tazemetostat (800 mg PO BID) in adults with advanced disease whose tumors harbor INI1 loss... there were 8 confirmed PRs with an ORR of 13% and DCR of 26%. Additionally, 35 pts had a best response of SD with 7 pts ongoing....In this study, the largest prospective clinical trial of ES to date, tazemetostat showed promising single agent activity, resulting in durable confirmed responses, a DCR of 26%, and favorable safety.