FDA Approves First Essential Thrombocythemia Drug in Nearly 30 Years

The U.S. Food and Drug Administration has approved ropeginterferon alfa-2b-njft (Besremi) for adults with essential thrombocythemia (ET), marking the first new drug approval for this rare blood cancer in nearly three decades. The decision gives patients and doctors a fresh option after a long period where treatment options remained stagnant. The treatment works through a subcutaneous injection given every two weeks, starting at a low dose and increasing over the first few weeks to a maintenance level.

Regulators based their decision on data from the SURPASS ET clinical trial, an open-label, multicenter study involving 174 adults with ET who had not responded well to hydroxyurea. In this study, participants were randomly assigned to receive either ropeginterferon alfa-2b or anagrelide. The trial used the modified European LeukemiaNet criteria to measure response rates at nine and twelve months. Results showed a significant difference between the two treatments. Patients receiving ropeginterferon achieved a durable response in 43% of cases compared to just 6% for those on anagrelide.

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The data also tracked changes in genetic markers associated with the disease. Over the course of a year, the mean JAK2 V617F allele burden decreased by 8.06% in the ropeginterferon group, while the anagrelide group saw an increase of 3.21%. Similarly, the mean CALR allele burden decreased by 5.32% with the new therapy versus a 1.45% decrease with the standard drug. The findings were presented at the 2025 American Society of Clinical Oncology Annual Meeting and published in The Lancet Haematology.

The trial results were published in The Lancet Haematology and presented at the 2025 American Society of Clinical Oncology Annual Meeting. The data shows that the new therapy can target the underlying genetic drivers of the disease more effectively than the standard option. This shift from purely managing blood counts to addressing the root cause of the condition represents a meaningful change for patients who have been managing symptoms for years without a real alternative. It suggests that future management of ET might focus less on symptom control and more on modifying the disease process itself.

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Doctors considering the drug for patients should be aware of the common adverse reactions. The most frequent side effects included transaminase elevations, anemia, fever, bacterial infection, pruritus, and weight loss. Because the treatment involves immunomodulation, patients will require regular blood tests and monitoring to manage these risks.

PharmaEssentia CEO Ko-Chung Lin, PhD, emphasized the company’s collaboration with regulators and healthcare providers to bring the treatment to the ET community. SURPASS ET investigator Ruben Mesa, MD, from the Atrium Health Levine Cancer Institute in Charlotte, noted that patients have long needed options that address the underlying disease rather than just managing symptoms. Ropeginterferon alfa-2b is a long-acting, monopegylated interferon alfa therapy and is also approved for treating polycythemia vera. Patients with ET who find their current treatments insufficient should discuss this option with their hematologist.