FDA Approves BESREMi for Essential Thrombocythemia, Expanding Treatment Options

The U.S. Food and Drug Administration (FDA) has approved BESREMi (ropeginterferon alfa-2b-njft) for the treatment of adults with essential thrombocythemia (ET), a rare blood cancer that causes the bone marrow to produce too many platelets.

The approval, announced by PharmaEssentia USA Corporation, makes BESREMi the first new FDA-approved treatment for essential thrombocythemia in nearly 30 years. The approval applies to adults with ET regardless of their genetic profile or disease status, including people who have been newly diagnosed and have not previously received cytoreductive therapy.

BESREMi was previously approved and marketed for adults with polycythemia vera (PV), another type of myeloproliferative neoplasm.

What Is Essential Thrombocythemia?

Essential thrombocythemia is a rare blood cancer and a type of myeloproliferative neoplasm, or MPN. In people with ET, the bone marrow produces too many platelets.

Although platelets normally help the blood clot, having too many can increase the risk of complications. People with ET may be at increased risk for blood clots, abnormal bleeding and an enlarged spleen. ET is often associated with genetic mutations, including mutations in the JAK2 gene.

Because ET is a chronic condition, many patients require long-term monitoring and treatment to help manage their disease and reduce the risk of complications such as stroke, heart attack and pulmonary embolism.

What Does the FDA Approval of BESREMi Mean for People With ET?

The approval gives adults with essential thrombocythemia another treatment option, including people who are newly diagnosed and have not previously received cytoreductive treatment.

BESREMi is a long-acting interferon-based therapy designed to provide sustained disease management. Unlike treatments that primarily focus on lowering platelet counts and managing symptoms, BESREMi is designed to target disease-driving cells in the bone marrow while reducing elevated platelet counts and disease burden.

"For nearly 30 years, people living with ET and the physicians treating them have had limited treatment innovation," said Ruben Mesa, M.D., principal investigator of the SURPASS-ET trial. "The approval of BESREMi provides an important new treatment option that is supported by strong clinical evidence and that also works at the source of the disease rather than solely managing symptoms."

How Effective Was BESREMi in Clinical Trials?

The FDA approval was supported by results from the global phase 3 SURPASS-ET clinical trial.

According to PharmaEssentia, BESREMi demonstrated durable modified European Leukemia Net (ELN) responses and durable hematologic control in adults with essential thrombocythemia. The treatment achieved superior durable response rates compared with anagrelide and reduced thromboembolic events over 12 months of treatment.

Research cited in the announcement also includes findings from the EXCEED-ET study, which evaluated ropeginterferon alfa-2b-njft in people with ET across different driver mutations.

What Are the Side Effects and Safety Concerns With BESREMi?

BESREMi carries a boxed warning because interferon alfa products can cause or worsen serious, potentially life-threatening or fatal neuropsychiatric, autoimmune, ischemic and infectious disorders. Patients receiving treatment should be closely monitored, and treatment should be withdrawn if serious or worsening symptoms persist.

BESREMi should not be used by people with a history of severe depression, suicidal thoughts or suicide attempts; certain liver problems; active serious or untreated autoimmune disease; or certain transplant histories involving immunosuppressive medications. It is also contraindicated in people with a hypersensitivity to interferons or the drug's inactive ingredients.

Doctors may also monitor patients for a range of potential complications, including depression, endocrine problems, cardiovascular toxicity, decreased blood counts, hypersensitivity reactions, pancreatitis, colitis, lung problems, eye disorders, elevated triglycerides, liver problems and kidney toxicity.

Patients should talk with their health care team about their individual medical history and the potential risks and benefits of BESREMi before starting treatment.

When Will BESREMi Be Available for Essential Thrombocythemia?

According to PharmaEssentia, BESREMi for essential thrombocythemia is expected to be available in the United States immediately following the FDA approval.

The approval expands the use of BESREMi beyond polycythemia vera and provides another option for adults living with essential thrombocythemia, a disease for which treatment innovation has been limited for decades.

References

1. PharmaEssentia Corporation. FDA Approves BESREMi® (ropeginterferon alfa-2b-njft) for Adults with Essential Thrombocythemia. August 31, 2026.
2. Reeves BN, El Chaer F, Foltz L, et al. Ropeginterferon alfa-2b-njft treatment in essential thrombocythemia across different driver mutations: results from a North American, single-arm, multicentre study (EXCEED-ET). Lancet Regional Health – Americas. 2026;61:101529.
3. Mesa R, Gill H, Zhang L, et al. Ropeginterferon alfa-2b in hydroxyurea-intolerant or hydroxyurea-refractory essential thrombocythaemia (SURPASS ET): a multicentre, open-label, randomised, active-controlled, phase 3 study. Lancet Haematology. 2025;12(11):e862-e875.
4. PharmaEssentia Corporation. BESREMi (ropeginterferon alfa-2b-njft) U.S. Prescribing Information.