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 myeloproliferative neoplasm characterized by the overproduction of platelets.
The approval, announced on August 31, 2026, expands the U.S. indication for PharmaEssentia’s long-acting interferon therapy, which is already approved for adults with polycythemia vera. According to PharmaEssentia, BESREMi is the first new FDA-approved treatment for essential thrombocythemia in nearly three decades.
BESREMi is approved for adults with ET regardless of genotype or disease status, including newly diagnosed patients who have not previously received cytoreductive therapy.
Phase 3 SURPASS ET Trial Supports FDA Approval
The approval was supported by data from the Phase 3 SURPASS ET trial (NCT04285086), an open-label, multicenter, randomized study comparing ropeginterferon alfa-2b with anagrelide in adults with essential thrombocythemia.
The trial enrolled 174 adults with ET who had an inadequate response or intolerance to hydroxyurea. Of these, 91 patients received BESREMi and 83 received anagrelide. Patients in both treatment groups also received low-dose aspirin unless contraindicated.
Efficacy was assessed using durable modified European Leukemia Net (ELN) response rates at months 9 and 12. To be considered responders, patients were required to achieve blood count remission, improvement or non-progression of splenomegaly, and an absence of bleeding or thrombotic events.
BESREMi achieved a durable response rate of 37.4%, compared with 3.6% with anagrelide, at both months 9 and 12.
PharmaEssentia also reported that BESREMi provided durable hematologic control and reduced thromboembolic events over 12 months of treatment.
Ruben Mesa, MD, principal investigator of the SURPASS ET trial and President of Advocate Health’s Cancer National Service Line, said:
“For nearly 30 years, people living with ET and the physicians treating them have had limited treatment innovation.”
Mesa emphasized that patients need treatment options that not only control blood counts but also address the underlying biology of essential thrombocythemia. He described BESREMi as an important new option backed by strong clinical evidence that acts at the source of the disease rather than focusing solely on symptom management.
A New Treatment Option for Essential Thrombocythemia
Essential thrombocythemia is a chronic myeloproliferative neoplasm in which the bone marrow produces excessive numbers of platelets. Patients may face an increased risk of blood clots and abnormal bleeding, as well as serious thrombotic complications such as heart attack, stroke, and pulmonary embolism.
BESREMi is a long-acting interferon-based therapy. PharmaEssentia states that its monopegylation technology and extended half-life allow it to target disease-driving cells in the bone marrow while reducing elevated platelet counts and disease burden.
The FDA-recommended starting dose of BESREMi is 250 mcg administered subcutaneously, increasing to 350 mcg at week 2 and 500 mcg at week 4. The maintenance dose is 500 mcg every two weeks unless dose modification is required because of tolerability.
The most commonly reported adverse reactions included elevated liver enzymes, anemia, fever, bacterial infection, pruritus, and weight loss. BESREMi carries a boxed warning regarding the risk of serious or life-threatening neuropsychiatric, autoimmune, ischemic, and infectious disorders.
According to PharmaEssentia, BESREMi for essential thrombocythemia is expected to be available in the United States immediately following the approval.
Read further on OncoDaily: FDA Approves Takeda’s Mimrylo (Rusfertide) for Polycythemia Vera
