Epizyme, Inc., a Cambridge-based clinical stage biopharmaceutical company creating novel epigenetic therapeutics for cancer patients, announced that the U.S. FDA has granted orphan drug status to the company’s first-in-class EZH2 inhibitor, tazemetostat, for the treatment of malignant rhabdoid tumors (MRTs). MRTs are rare and aggressive cancers with poor outcomes. Currently, treatment of MRT consists of surgery, chemotherapy and radiation therapy, which are associated with limited efficacy and significant treatment-related morbidity. MRT is a tumor defined by loss of INI1 protein as measured by immunohistochemistry. Other rhabdoid tumors, such as MRT of ovary, are characterized by loss of the protein SMARCA4 and have shown sensitivity to tazemetostat in preclinical models and in our phase 1 study. The orphan drug designation applies to both INI1-negative MRT as well as SMARCA4-negative MRT of ovary.