The FDA has granted Orphan Drug status to Epizyme’s first-in-class EZH2 inhibitor, tazemetostat, for the treatment of malignant rhabdoid tumors (MRTs). In December 2015, the company initiated a phase II study in adults and a phase I study in children with genetically defined tumors, including MRTs. Tazemetostat is also being investigated in an ongoing five-arm phase II study in patients with non-Hodgkin lymphoma.

“Malignant rhabdoid tumors are rare and aggressive cancers with poor outcomes. There have not yet been any targeted drugs developed specifically to treat these patients,” said Peter Ho, M.D., Ph.D., chief medical officer, Epizyme. “In an ongoing phase I study, tazemetostat has demonstrated encouraging clinical activity and an acceptable safety profile in patients with these severe types of cancer. We believe tazemetostat has the potential to become an important targeted therapy for patients with MRT and we are working aggressively to execute our clinical development program.”

Orphan Drug designation provides the sponsor of the drug with eligibility for various development incentives, including tax credits for qualified clinical testing and marketing exclusivity for a period of seven years. Therapies with orphan drug status are also not subject to a prescription drug user fee for the orphan indication.

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 I study. The Orphan Drug designation applies to both INI1-negative MRT as well as SMARCA4-negative MRT of ovary.

The ongoing phase II adult and phase I pediatric studies in patients with genetically-defined solid tumors include patients with rhabdoid tumors, other INI1-negative tumors, and synovial sarcoma. Interim data from Epizyme’s registration-supporting phase II clinical study of tazemetostat in adult patients with genetically defined solid tumors, including MRT, other INI1-negative tumors and synovial sarcoma, are anticipated to be presented at a medical conference in late 2016.