Metastatic disease is considered life-threatening to the patient.According to the NCI Drug Dictionary, "tazemetostat is an orally available, small molecule selective and S-adenosyl methionine (SAM) competitive inhibitor of histone methyl transferase EZH2, with potential antineoplastic activity. Upon oral administration, tazemetostat selectively inhibits the activity of both wild-type and mutated forms of EZH2. Inhibition of EZH2 specifically prevents the methylation of histone H3 lysine 27 (H3K27). This decrease in histone methylation alters gene expression patterns associated with cancer pathways and results in decreased tumor cell proliferation in EZH2 mutated cancer cells. EZH2, which belongs to the class of histone methyltransferases (HMTs), is overexpressed or mutated in a variety of cancer cells and plays a key role in tumor cell proliferation. "The U.S. Food and Drug Administration (FDA) considers it to be a first-in-class medication. History
The U.S. Food and Drug Administration (FDA) approved tazemetostat in January 2020, based on the results of a clinical trial (NCT02601950) enrolling 62 subjects with metastatic or locally advanced epithelioid sarcoma. During the clinical trial, subjects received 800 milligrams (mg) of tazemetostat twice a day until the disease progressed or the subject reached an unacceptable level of toxicity. Tumor response assessments were performed every eight weeks during the clinical trial. The trial measured how many subjects experienced complete or partial shrinkage (by a certain amount) of their tumors during treatment (overall response rate). The overall response rate was 15%, with 1.6% of subjects having a complete response and 13% having a partial response.
Of the nine subjects that had a response, six (67%) subjects had a response lasting six months or longer.The trial was conducted at 22 sites in France, United Kingdom, Taiwan, Italy, Canada, Belgium, and the United States.The FDA granted the application for tazemetostat accelerated approval and orphan drug designation. The FDA granted the approval of Tazverik to Epizyme Inc.

References
External links
"Tazemetostat". Drug Information Portal. U.S. National Library of Medicine.