FDA Warns of Increased Risk of New Blood Cancers with Tazverik; Manufacturer Withdraws U.S. Indications After Trial Findings

May 14, 2026

The U.S. Food and Drug Administration (FDA) issued a critical safety alert this week, warning healthcare providers and patients that the cancer drug Tazverik (tazemetostat) is associated with a significantly increased risk of developing new, secondary blood cancers. Following data from a late-stage clinical trial showing that the drug’s risks now outweigh its clinical benefits, the drug’s sponsor, Ipsen, has moved to voluntarily withdraw Tazverik from the U.S. market for its approved indications.

The decision follows alarming safety signals from the SYMPHONY-1 trial, where patients treated with Tazverik developed secondary malignancies—specifically bone marrow disorders—at a rate far exceeding those in the control group. The FDA and the manufacturer are now urging immediate clinical reviews for all patients currently prescribed the medication.

The SYMPHONY-1 Findings: A Shift in Risk

Tazverik, an EZH2 inhibitor, originally received accelerated approval in 2020. This regulatory pathway allows drugs for serious conditions to reach the market based on early evidence, provided the manufacturer conducts “confirmatory” trials to prove long-term safety and efficacy.

The SYMPHONY-1 trial (NCT04224493) served as that confirmatory study. However, instead of confirming the drug’s safety profile, the Phase 1b/3 study revealed a troubling trend in patients with relapsed or refractory follicular lymphoma.

Key Statistical Data:

• Incidence Rate: Out of 318 patients receiving Tazverik, 18 individuals (5.7%) developed hematologic second primary malignancies (SPMs). In stark contrast, zero patients in the control arm developed these cancers.

• Types of Cancer: The majority of these secondary cancers were Myelodysplastic Syndrome (MDS) and Acute Myeloid Leukemia (AML)—both aggressive forms of blood and bone marrow disorders.

• Timeline: While the median treatment duration was approximately 15.8 months, the earliest case of secondary cancer appeared just 7.5 months after starting therapy.

• Fatalities: Among the 18 affected patients, three deaths were directly attributed to these new, treatment-emergent leukemias or MDS.

Expert Perspectives on Accelerated Approval

The withdrawal of Tazverik highlights the inherent “double-edged sword” of the FDA’s accelerated approval process. While the pathway provides early access to life-saving drugs, it relies on the assumption that post-market data will remain favorable.

“Accelerated approvals often rest on limited, early-stage evidence,” noted oncology analysts in reports following the FDA alert. When confirmatory studies like SYMPHONY-1 reveal new safety signals, regulatory reappraisal is the necessary mechanism to protect public health.

The FDA’s formal assessment concluded that the “risks of treatment with Tazverik outweigh its benefits.” An independent data monitoring committee took the rare step of advising an immediate halt to trial enrollment and recommending that current participants discontinue the drug entirely.

Context and Background: Why the Change?

When Tazverik was first approved for metastatic epithelioid sarcoma and follicular lymphoma, its labeling did include a warning about secondary malignancies. At that time, the estimated incidence was approximately 1.7%.

However, the new data from the SYMPHONY-1 trial pushed that incidence rate above 5%. This three-fold increase fundamentally altered the risk-benefit calculus for regulators.

In response to these signals, Ipsen notified global regulators of its plans to discontinue treatment in the trial and withdraw the product from the U.S. market. While the trial will continue for the sole purpose of long-term safety follow-up, all expanded access programs have been shuttered.

Clinical Implications: What Happens Now?

For the medical community, the immediate priority is patient safety and transition of care. The FDA and Ipsen have provided specific directives for clinicians:

1. Immediate Discontinuation: Participants in the SYMPHONY-1 trial must stop taking Tazverik immediately.

2. Patient Review: Clinicians must review the status of any patient currently on the drug to weigh the risks of sudden cessation against the risks of developing MDS or AML.

3. Vigilant Monitoring: Doctors are advised to monitor patients for cytopenias (low blood cell counts) or any signs of marrow dysfunction. This includes regular peripheral blood counts and smears.

“The withdrawal underscores the importance of long-term safety data,” a regulatory spokesperson noted. “Prescribers must always balance early access to promising therapies against the evolving evidence that emerges after a drug hits the shelves.”

What Patients and Caregivers Should Know

If you or a loved one is currently taking Tazverik, it is natural to feel concerned. However, medical experts emphasize that you should not stop therapy without first consulting your oncology team.

Symptoms to Watch For:

Patients who have been exposed to Tazverik should be alert for symptoms of bone marrow failure or new blood cancers, including:

• Unusual or worsening fatigue or weakness.

• Easy bruising or unexplained bleeding.

• Frequent infections.

• Persistent, unusual fevers.

If these symptoms occur, seek medical attention immediately. Your oncologist may recommend long-term hematologic surveillance depending on how long you were treated with the drug.

Limitations and Future Outlook

While the safety signal is clear, some experts note that the SYMPHONY-1 data specifically looked at Tazverik in combination with other drugs (lenalidomide and rituximab) for follicular lymphoma. It remains to be seen if the risk is as high when the drug is used as a standalone therapy or for other types of cancer.

Nevertheless, the FDA’s decision reflects a population-level safety standard. As international regulators begin to reassess the drug’s availability in other markets, the case serves as a stark reminder of the rigor required in post-market surveillance.

Medical Disclaimer

Medical Disclaimer: This article is for informational purposes only and should not be considered medical advice. Always consult with qualified healthcare professionals before making any health-related decisions or changes to your treatment plan. The information presented here is based on current research and expert opinions, which may evolve as new evidence emerges.

References

• https://www.medscape.com/viewarticle/fda-warns-secondary-blood-cancer-risk-tazverik-2026a1000fil