The FDA Approval landscape for essential thrombocythemia (ET) is continuing to evolve as researchers and hematologists gain a better understanding of the biology of myeloproliferative neoplasms (MPNs). A significant recent development is the U.S. Food and Drug Administration (FDA) approval of ropeginterferon alfa-2b-njft (Besremi) for the treatment of adults with essential thrombocythemia.
The approval was supported by findings from the SURPASS-ET clinical trial, a phase 3 study that evaluated ropeginterferon alfa-2b against anagrelide in patients with ET who had resistance or intolerance to hydroxyurea.
For clinicians following developments in MPN treatment, SURPASS-ET provides important information about response rates, treatment tolerability, molecular disease markers, and the potential role of interferon-based therapy in ET.
Understanding Essential Thrombocythemia
Essential thrombocythemia is a chronic myeloproliferative neoplasm characterized by the production of excessive platelets by the bone marrow. Abnormally high platelet levels can contribute to complications including thrombosis and, in some circumstances, bleeding.
ET is also associated with molecular abnormalities involving driver mutations such as JAK2, CALR, and MPL. These molecular characteristics can provide additional information when physicians evaluate disease biology and treatment response.
Treatment decisions are individualized according to factors such as age, previous thrombotic events, cardiovascular risk, symptoms, blood counts, molecular findings, previous therapies, and treatment tolerance.
What Is the SURPASS-ET Study?
SURPASS-ET was a randomized, open-label, multicenter phase 3 clinical trial comparing ropeginterferon alfa-2b with anagrelide as second-line treatment for selected patients with essential thrombocythemia.
The study enrolled adults with high-risk ET who were resistant or intolerant to hydroxyurea. A total of 174 patients were randomized, with 91 receiving ropeginterferon alfa-2b and 83 receiving anagrelide.
The primary endpoint evaluated durable response at months 9 and 12 using modified European LeukemiaNet criteria.
The results showed a notable difference between the treatment groups. Durable response was observed in 39 of 91 patients (43%) receiving ropeginterferon alfa-2b compared with 5 of 83 patients (6%) receiving anagrelide.
These findings formed an important part of the evidence supporting the subsequent FDA approval of ropeginterferon alfa-2b for adults with essential thrombocythemia.
FDA Approval of Ropeginterferon Alfa-2b for ET
In August 2026, the FDA approved Besremi (ropeginterferon alfa-2b-njft) for the treatment of adults with essential thrombocythemia.
The FDA describes SURPASS-ET as an open-label, multicenter, randomized study comparing Besremi with anagrelide. The current prescribing information includes a starting dose of 250 mcg administered subcutaneously, followed by 350 mcg at week 2 and a maintenance dose of 500 mcg from week 4, with administration every two weeks unless dose modification is needed for tolerability.
This approval expands the established role of ropeginterferon alfa-2b beyond its previous use in polycythemia vera and gives physicians another treatment option for adults with ET.
Ropeginterferon Alfa-2b vs. Anagrelide
One of the central questions addressed by SURPASS-ET was how ropeginterferon alfa-2b compares with anagrelide.
In the trial, ropeginterferon alfa-2b produced a substantially higher durable modified-ELN response rate than anagrelide in the studied population. The published results reported grade 3 or worse treatment-emergent adverse events in 23% of patients in the ropeginterferon group compared with 34% in the anagrelide group. Serious adverse events occurred in 14% and 30% of patients, respectively.
However, clinical treatment decisions involve more than response rates alone. Physicians must consider individual patient characteristics, previous treatments, adverse-event profiles, dosing preferences, comorbidities, and other factors when selecting therapy.
The Importance of Disease Modification
One of the broader areas of interest surrounding interferon-based therapy is the concept of disease modification.
Traditional cytoreductive treatment in ET primarily focuses on controlling blood counts and reducing complications associated with thrombosis or bleeding. Interferon-based approaches have generated interest because of their potential effects on the underlying clonal disease.
Molecular response is therefore an important area of research. In particular, clinicians may monitor changes in the JAK2 V617F allele burden in patients who carry the mutation.
A reduction in allele burden can provide information about molecular response, although molecular markers should be interpreted together with clinical findings and hematologic response rather than being viewed as an isolated measure of treatment success.
JAK2 Allele Burden and ET
JAK2 V617F is one of the major driver mutations associated with myeloproliferative neoplasms.
Monitoring JAK2 allele burden can help physicians understand how the molecular characteristics of the disease change over time. The potential for interferon therapy to produce molecular responses has consequently become an important area of investigation in ET and other MPNs.
Recent North American EXCEED-ET data also reported molecular responses across different driver mutations, including JAK2, CALR, and MPL, further contributing to research into the molecular effects of ropeginterferon in ET.
Treatment Considerations for Younger Patients
Age and long-term treatment considerations can play an important role when physicians discuss therapy for patients with ET.
For younger patients, clinicians may consider the expected duration of treatment, potential adverse effects, reproductive considerations, and the patient's individual disease characteristics.
The potential role of interferon-based treatment in younger patients has therefore received considerable attention within the MPN community. However, treatment decisions should always be individualized and made with an appropriate hematology specialist.
Managing Side Effects
As with any treatment, understanding and managing adverse effects is an important part of therapy with ropeginterferon alfa-2b.
The SURPASS-ET experience provides additional information about the safety and tolerability of ropeginterferon compared with anagrelide. The published study reported differences in both severe and serious adverse events between the two groups.
More recent EXCEED-ET data in a North American ET population reported that most treatment-emergent adverse events were mild, with fatigue and reversible transaminase elevations among commonly reported events.
Monitoring and proactive management can be important for helping patients remain on treatment when clinically appropriate.
Expert Perspective on SURPASS-ET
The SURPASS-ET findings have also generated discussion among MPN specialists regarding how ropeginterferon alfa-2b may fit into the broader treatment strategy for essential thrombocythemia.
In an Oncology Brothers podcast discussion, Dr. John Mascarenhas, an MPN specialist from Mount Sinai, provided an expert perspective on the SURPASS-ET study and the FDA approval of ropeginterferon alfa-2b.
The discussion covers the study design, response results, comparison with anagrelide, side-effect management, disease modification, JAK2 allele burden, dosing considerations, and the potential role of treatment in younger patients.
For readers looking for a more detailed expert discussion of these developments, the Oncology Brothers SURPASS-ET resource provides additional context on the clinical trial and its implications for ET treatment.
What SURPASS-ET Means for the ET Treatment Landscape
The SURPASS-ET results add important evidence to the growing body of research surrounding interferon-based treatment for essential thrombocythemia.
The trial demonstrated a higher durable modified-ELN response rate with ropeginterferon alfa-2b than with anagrelide in the studied population, while also providing additional information about safety and tolerability.
The FDA approval in 2026 represents another development in the management of adults with ET and gives clinicians an additional approved treatment option.
At the same time, ongoing research is examining longer-term outcomes, molecular responses, treatment durability, and how ropeginterferon may be used across different patient populations.
Looking Ahead
The management of essential thrombocythemia is increasingly influenced by both clinical and molecular considerations.
As research continues, questions surrounding disease modification, molecular response, long-term safety, and individualized treatment selection will remain important areas of investigation.
SURPASS-ET provides valuable evidence regarding the use of ropeginterferon alfa-2b in patients with ET who have limited options following hydroxyurea resistance or intolerance. The findings, together with the 2026 FDA approval and emerging data from other studies, contribute to a changing treatment landscape for myeloproliferative neoplasms.
For healthcare professionals interested in the clinical discussion surrounding SURPASS-ET, the Oncology Brothers' dedicated resource offers an additional expert perspective on ropeginterferon alfa-2b, essential thrombocythemia, anagrelide, JAK2 allele burden, disease modification, and treatment management.
Medical Disclaimer:
This article is intended for educational and informational purposes only. It is not a substitute for professional medical advice, diagnosis, or treatment. Treatment decisions for essential thrombocythemia should be made by a qualified healthcare professional based on the individual patient's clinical circumstances.
