FDA Approves BESREMi® for Adults with Essential Thrombocythemia

Ropeginterferon alfa-2b expands beyond polycythemia vera and opens a new phase in ET treatment.

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 chronic myeloproliferative neoplasm characterized by the overproduction of platelets.

This approval represents an important step for the MPN community, as BESREMi, already known for its use in polycythemia vera (PV) in several countries, now expands into another disease within the group of myeloproliferative neoplasms (MPN).

According to the FDA and PharmaEssentia, BESREMi becomes the first new FDA-approved treatment for essential thrombocythemia in nearly three decades.

From polycythemia vera to essential thrombocythemia

BESREMi is a long-acting interferon-based therapy. Its role in polycythemia vera was already established in different countries, and its expansion into essential thrombocythemia reflects an important development in the MPN treatment landscape.

In June 2026, Taiwan became the first country worldwide to approve BESREMi for adults with ET. The medicine later received regulatory approval for ET in Japan and, on August 31, 2026, in the United States.

For patients and families, this news matters because it shows that research continues to move toward more disease-focused options within different MPNs. Although PV and ET share some features as chronic bone marrow diseases, each has its own challenges and requires individualized treatment decisions.

What is essential thrombocythemia?

Essential thrombocythemia is a rare blood disorder in which the bone marrow produces too many platelets. Platelets are small cell fragments that help blood clot, but when platelet counts are very high, the risk of complications such as blood clots or bleeding may increase.

ET management may include observation, low-dose aspirin in selected patients, and treatments to reduce platelet counts when clinically needed. Treatment choice depends on several factors, including age, history of thrombosis or bleeding, symptoms, blood counts, mutations and each person’s overall health.

The SURPASS ET study

The FDA approval of BESREMi in the United States was supported by results from SURPASS ET, an open-label, multicenter, randomized Phase 3 study comparing BESREMi with anagrelide in adults with essential thrombocythemia who had an inadequate response or intolerance to hydroxyurea.

The study enrolled 174 adults with ET. According to the FDA, at Months 9 and 12, treatment with BESREMi showed a response rate of 37.4%, compared with 3.6% in the anagrelide treatment group. Evaluation included criteria such as blood count control, improvement or non-progression of splenomegaly, and absence of bleeding or clotting events.

These data represent an important signal in a disease area where new treatment options have long been needed.

A new step in the MPN treatment landscape

The approval of BESREMi for ET should not be interpreted to mean that every person with essential thrombocythemia should receive this treatment. In MPN care, treatment decisions must always be adapted to each individual patient.

However, this approval does mark a new chapter. The expansion of ropeginterferon alfa-2b from polycythemia vera into essential thrombocythemia reflects a broader trend: developing treatments that may better respond to the biology of these diseases and to the real needs of people living with them.

The FDA also notes that the most common adverse reactions included transaminase elevations, anemia, fever, bacterial infection, pruritus and weight loss. As with interferon alfa products, BESREMi requires medical follow-up and regular clinical and laboratory monitoring.

What does this approval mean internationally?

BESREMi is currently approved for essential thrombocythemia in the United States, Taiwan and Japan. This does not mean that it is automatically approved for ET in other countries or regions, where each regulatory authority must conduct its own evaluation process.

For the international MPN community, this approval is significant because it reflects research and development progress beyond a single disease. Expanding therapeutic strategies across different MPNs may open new questions, new opportunities and new conversations among patients, hematologists, researchers and health authorities.

At Global MPN Scientific Foundation, we will continue to follow the regulatory, clinical and real-world evolution of BESREMi in essential thrombocythemia, as well as its role within the broader treatment landscape of myeloproliferative neoplasms.

Patients should always discuss treatment decisions with their hematologist or MPN specialist, taking into account their individual disease characteristics, symptoms, blood counts, treatment history and overall health.

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