The enhancer of zeste homologue 2 (EZH2) inhibitor tazemetostat is under testing in adults with diffuse large B cell lymphoma or SMARCB1-negative or SMARCA4-negative solid tumors, and in pediatric patients with rhabdoid tumors, synovial sarcoma, epithelioid sarcoma, or other cancers with SMARCB1, SMARCA4, or EZH2 mutations [64,65,66,67]. The gene discussed is SMARCB1; the disease is synovial sarcoma.