The FDA is alerting patients and health care providers about the voluntary withdrawal of Tazverik (tazemetostat) tablets from the market due to an increased rate of hematologic second primary malignancies - the development of new blood cancers in people treated with Tazverik for a different cancer. The agency has determined that the risks of treatment with Tazverik outweigh its benefits.
Tazverik was approved in 2020 under accelerated approval to treat individuals aged 16 years and older with metastatic or locally advanced epithelioid sarcoma who are not eligible for complete resection, and later that year for certain adults with relapsed or refractory follicular lymphoma. At the time of accelerated approval, second primary malignancies were recognized as a risk with an incidence rate of 1.7%. However, in the Symphony 1 trial (NCT04224493), the rate was found to exceed 5% over a median treatment duration of 15.8 months.
In the SYMPHONY-1 study—a Phase 1b/3 double-blind, randomized, active-controlled trial evaluating tazemetostat or placebo in combination with lenalidomide plus rituximab in patients with relapsed/refractory follicular lymphoma—18 out of 318 patients (5.7%) treated with Tazverik developed hematologic second primary malignancies as of March 6, 2026, compared to no reported events in the control arm. Most cases were myelodysplastic syndrome and acute myeloid leukemia, with others including B-cell acute lymphoblastic leukemia and clonal cytopenia of undetermined significance.
Treatment-emergent acute leukemias and MDS are serious and life-threatening disorders that are not expected to be reversible, as evidenced by 3 deaths among the 18 patients and 14 patients without resolution of the hematologic second primary malignancy. Most participants who developed the new blood cancers were receiving Tazverik for 1-3 years, with events starting as early as 7.5 months after beginning treatment and occurring in some patients after stopping treatment.
Based on these findings, an independent data monitoring committee recommended that enrollment on the SYMPHONY-1 trial should be stopped and that all patients receiving Tazverik should discontinue treatment immediately. Shortly thereafter, sponsor Ipsen notified FDA of its plans to discontinue Tazverik treatment for patients in the clinical study and withdraw Tazverik from the U.S. market. The study will remain open for long-term safety follow-up of participants, and all expanded access programs for Tazverik will be discontinued.
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