On January 23, 2020, the FDA granted accelerated approval to tazemetostat (Tazverik; Epizyme), a methyltransferase inhibitor, for the treatment of metastatic or locally advanced epithelioid sarcoma in adults and pediatric patients aged ≥16 years who are not eligible for complete resection.
“For people with epithelioid sarcoma, an aggressive life-threatening cancer that affects young adults, having new treatment options can offer much-needed hope,” said Denise Reinke, MS, NP, MBA, President and Chief Executive Officer, Sarcoma Alliance for Research Through Collaboration, and Co-Founder, Sarcoma Coalition, in a press release.
This approval was based on improvements in overall response rate (ORR) and duration of response (DOR) in a phase 2 clinical trial. Verification and description of clinical benefit in a confirmatory clinical trial(s) may be necessary for continued approval of tazemetostat for this indication.
- The efficacy of tazemetostat was evaluated in a phase 2, open-label, single-arm cohort (Cohort 5) of a multicenter study in patients with histologically confirmed, metastatic, or locally advanced epithelioid sarcoma. Patients were required to have INI1 protein loss, detected using local tests, and an Eastern Cooperative Oncology Group performance status of 0-2.
- Patients received tazemetostat 800 mg orally twice daily until disease progression or unacceptable toxicity. Tumor response assessments were performed every 8 weeks. The major efficacy outcome measures were confirmed ORR according to Response Evaluation Criteria in Solid Tumors v1.1 as assessed by blinded independent central review and DOR. Median duration of follow-up was 14 months (range, 0.4-31).
- Of the 62 patients treated in Cohort 5, the ORR was 15%, with 1.6% achieving a complete response, and 13% achieving a partial response. Among the responders, 67% had a DOR ≥6 months.
- The most common (≥20%) adverse reactions were pain, fatigue, nausea, decreased appetite, vomiting, and constipation.
- Tazemetostat increases the risk for secondary malignancies, such as T-cell lymphoma, myelodysplastic syndrome, and acute myeloid leukemia.
- Tazemetostat can cause fetal harm. Patients should be advised of potential risk to a fetus and to use effective nonhormonal contraception.