Loading ...

The US FDA has issued a safety alert over an increased risk of secondary primary blood cancers in patients treated with tazemetostat (Tazverik, Ipsen), stating that the drug’s risks now “outweigh its benefits.”

The alert advised all patients currently receiving tazemetostat to immediately discontinue treatment and called on clinicians to monitor patients for delayed hematologic malignancies even after discontinuation of therapy. 

Ipsen is withdrawing the drug from the US and all other markets because of the risk of secondary hematologic malignancies, as Medscape Medical News previously reported. 

The FDA granted accelerated approval to tazemetostat in 2020 for patients aged 16 years and older with metastatic or locally advanced epithelioid sarcoma who are not eligible for complete resection. Later that year, the agency approved the drug for adults with relapsed or refractory follicular lymphoma whose tumors have an EZH2 mutation. 

At the time of accelerated approval, hematologic secondary malignancies were already recognized as a potential risk with tazemetostat, with an incidence of approximately 1.7%. 

However, subsequent data from the phase 3 SYMPHONY-1 trial in relapsed or refractory follicular lymphoma showed a substantially higher rate. 

As of March 6, 2026, 18 of 318 patients (5.7%) treated with tazemetostat in combination with lenalidomide and rituximab developed hematologic second malignancies, compared with no cases in the control group. 

Most malignancies were myelodysplastic syndrome and acute myeloid leukemia. Other reported cases included B-cell acute lymphoblastic leukemia and clonal cytopenia of undetermined significance. Three patients died, and most cases had not resolved at the time of analysis. 

Most participants who developed the secondary blood cancers had received tazemetostat for 1-3 years. Blood cancers developed as early as 7.5 months after treatment initiation and, in some cases, occurred after treatment discontinuation. 

Based on these findings, an independent data monitoring committee recommended halting enrollment in the SYMPHONY-1 trial and discontinuing treatment in all patients receiving the drug.

The trial will remain open for long-term safety follow-up of participants.

Adverse events associated with tazemetostat should be reported to the FDA through MedWatch, the agency’s adverse event reporting program.