Tazemetostat (Tazverik) has received accelerated approval for the treatment of adults and pediatric patients ages 16 years and older with metastatic or locally advanced epithelioid sarcoma who are not eligible for complete resection. Epithelioid sarcoma occurs mostly in teenagers or young adults and often presents as small, firm growths in deep soft tissue or under the skin of the fingers, hands, forearms, lower legs, or feet. Because the initial lesion can ulcerate, it can be misdiagnosed as a skin ulcer that isn't healing. Most patients do not have pain with the initial growth. Lymph node metastasis is common with this form of cancer.

Tazemetostat blocks the activity of zeste homolog 2 (EZH2) methyltransferase, which helps to keep the cancer cells from growing.

Tazemetostat was granted accelerated approval and received orphan drug designation. Sixty-two patients with epithelioid sarcoma were enrolled in an open-label, single-arm multicenter study and received tazemetostat 800 mg orally twice a day until disease progression or unacceptable toxicity occurred. The overall response rate (the proportion of patients who achieved complete or partial tumor shrinkage) was 15% (nine of 62 patients), with 1.6% of patients having a complete response and 13% having a partial response. Of the nine patients who had a response, six (67%) had a response lasting six months or longer.

Tazemetostat use may lead to secondary malignancies as well as produce embryo-fetal toxicity. The most common adverse effects include pain, fatigue, nausea, decreased appetite, vomiting, and constipation. Interactions are possible with other drugs metabolized via the cytochrome P-450 (CYP) 3A pathway. Coadministration of tazemetostat with strong to moderate CYP3A inhibitors should be avoided as this will increase the circulating levels of tazemetostat. Conversely, strong to moderate CYP3A inducers should also be avoided as they will decrease the circulating levels of tazemetostat.

Nurses should assess for potential drug interactions and tell patients about the risk of embryo-fetal toxicity and to use effective birth control while on this drug.

For complete prescribing information for tazemetostat, go to http://www.accessdata.fda.gov/drugsatfda_docs/label/2020/211723s000lbl.pdf.