Ipsen Voluntarily Withdraws Tazverik After Confirmatory Trial Links Drug to 5.7% Blood Cancer Rate

Confirmatory trial data have done precisely what accelerated approval pathways are designed to allow: forced a market exit. Ipsen will voluntarily withdraw Tazverik (tazemetostat) from the U.S. market after the SYMPHONY-1 trial recorded hematologic second primary malignancies (SPMs) in 5.7% of treated patients, against zero events in the control arm, as of March 6, 2026.

Tazverik received FDA accelerated approval in 2020 for two oncology indications: metastatic or locally advanced epithelioid sarcoma in patients aged 16 and older ineligible for complete resection, and relapsed or refractory follicular lymphoma in certain adults. At the time of approval, SPMs were a labeled risk at an incidence of 1.7%. The SYMPHONY-1 Phase 1b/3 randomized study, designed to confirm clinical benefit in follicular lymphoma, returned an SPM rate exceeding 5% over a median treatment duration of 15.8 months, a threshold that shifted the benefit-risk calculus decisively.

Of the 18 affected patients out of 318 treated, the predominant SPM types were myelodysplastic syndrome (MDS) and acute myeloid leukemia, with additional cases of B-cell acute lymphoblastic leukemia and clonal cytopenia of undetermined significance. Three patients died; 14 showed no resolution of the hematologic SPM. Events began as early as 7.5 months into treatment and were observed in some patients after treatment discontinuation, a finding with direct implications for long-term pharmacovigilance protocols.

The independent data monitoring committee recommended immediate enrollment cessation and discontinuation of Tazverik in all current patients. Ipsen subsequently notified FDA of plans to withdraw the product from the U.S. market. All expanded access programs will also be discontinued. The SYMPHONY-1 study will remain open for long-term safety follow-up of participants, preserving the post-market surveillance record.

For regulatory affairs and QA teams, the case illustrates the operational weight of accelerated approval commitments under 21 CFR Part 312 and the agency's post-market authority. When confirmatory data materially exceed the SPM incidence documented at approval, the regulatory framework provides limited room for negotiation on continued commercialization. Pharmacovigilance functions should treat the SYMPHONY-1 dataset as a reference point when calibrating SPM monitoring thresholds in oncology programs carrying similar EZH2-inhibitor mechanisms.

The long-term safety follow-up cohort from SYMPHONY-1 will generate the next measurable outcome: whether SPM incidence stabilizes or continues to accrue after treatment discontinuation, a data point that will inform both the final benefit-risk assessment and any future labeling precedent for the EZH2 inhibitor class.

Source: U.S. Food and Drug Administration, FDA Drug Alerts and Statements (What's New: Drugs RSS Feed), May 11, 2026.