FDA Warns of New Blood Cancer Risk With Tazemetostat
USA: The FDA has alerted healthcare providers about an increased risk of developing new primary hematologic malignancies (blood cancers) in patients treated with Tazverik (tazemetostat), a drug used for certain sarcomas and lymphomas. Following these safety concerns, the medication is being withdrawn from global markets.
The U.S. Food and Drug Administration (FDA) issued the warning after emerging data showed a higher-than-expected occurrence of secondary blood cancers, also referred to as hematologic second primary malignancies (SPMs), among patients receiving Tazverik. These findings prompted a reassessment of the drug’s safety profile, with regulators concluding that the potential risks now outweigh its therapeutic benefits.
Tazverik, also known as tazemetostat, was granted accelerated approval in 2020 for patients aged 16 years and older with metastatic or locally advanced epithelioid sarcoma who were not candidates for complete surgical removal. Later the same year, its use was extended to certain adults with relapsed or refractory follicular lymphoma, a typically slow-growing B-cell malignancy. At the time of approval, a small risk of secondary cancers was recognized, with an incidence of approximately 1.7%.
However, updated evidence from the SYMPHONY-1 clinical trial has raised significant concerns. The study, a large randomized and controlled investigation evaluating tazemetostat in combination with lenalidomide and rituximab in patients with relapsed or refractory follicular lymphoma, demonstrated a marked increase in the incidence of hematologic SPMs. As of March 2026, 18 out of 318 patients (5.7%) receiving Tazverik developed new blood cancers, whereas no such cases were reported in the control group.
The majority of these secondary malignancies included serious conditions such as myelodysplastic syndrome and acute myeloid leukemia. Other reported cases involved B-cell acute lymphoblastic leukemia and clonal cytopenia of undetermined significance. These conditions are considered severe and potentially life-threatening, with limited reversibility. Among the affected patients, three deaths were reported, while most others did not show resolution of the newly developed malignancies.
Notably, the onset of these cancers was observed after prolonged exposure, typically between one and three years of treatment. In some cases, the malignancies appeared as early as 7.5 months after initiating therapy, and a few cases were identified even after treatment discontinuation.
In light of these findings, an independent data monitoring committee recommended halting further enrollment in the SYMPHONY-1 trial and advised immediate discontinuation of Tazverik for all participants. Subsequently, the drug’s manufacturer, Ipsen, informed the FDA of its decision to stop treatment within the trial and voluntarily withdraw the drug from the U.S. market. The study will continue for long-term safety monitoring of enrolled patients, while expanded access programs for the drug are also being discontinued.
The FDA has urged clinicians to carefully evaluate ongoing treatment plans and consider alternative therapeutic options for patients previously receiving Tazverik.
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