A pediatric phase 1 study was conducted in children with relapsed or refractory malignant rhabdoid tumor, atypical teratoid rhabdoid tumor, other SMARCB1-deficient tumors, or synovial sarcoma and saw responses in 14% of tumors in the dose expansion cohort population, with a 24% response rate in ATRT15. The gene discussed is SMARCB1; the disease is synovial sarcoma.