The U.S. Food and Drug Administration (FDA) has approved BESREMi® (ropeginterferon alfa-2b-njft), developed by PharmaEssentia USA Corporation, for the treatment of adults with essential thrombocythemia (ET), marking the first new FDA-approved therapy for ET in nearly three decades. The approval is supported by data from the global Phase 3 SURPASS-ET trial and extends BESREMi’s existing label, which previously covered adults with polycythemia vera (PV).

Clinical Takeaway

BESREMi is now FDA-approved for adults with ET regardless of genotype or disease status, including treatment-naïve patients. As a long-acting interferon-based therapy, BESREMi is designed to act on underlying disease biology in the bone marrow while reducing elevated platelet counts and disease burden, offering the potential for durable disease control — a meaningful advance for a patient population that has lacked a new FDA-approved treatment for nearly three decades.

Drug Profile & Mechanism

  • Drug name: BESREMi® (ropeginterferon alfa-2b-njft)
  • Drug class: Long-acting, monopegylated interferon alfa-2b
  • Developer: PharmaEssentia Corporation
  • Mechanism: Utilizes monopegylation technology and an extended half-life and is designed to target disease-driving cells in the bone marrow while reducing elevated platelet counts and overall disease burden
  • Differentiation from current therapies: Existing ET treatments such as hydroxyurea and anagrelide are primarily used for cytoreduction; BESREMi provides a long-acting interferon-based approach designed to address underlying disease biology in addition to controlling blood counts

Target Population

  • Approved indication: Adults with essential thrombocythemia (ET)
  • Genotype restriction: None — approved regardless of genotype
  • Prior therapy requirement: None — includes patients who are naïve to cytoreductive therapy
  • Disease context: ET is a rare chronic myeloproliferative neoplasm (MPN) characterized by overproduction of platelets, with patients at elevated risk for serious thromboembolic complications including heart attack, stroke, and pulmonary embolism

Study Design

  • Trial name: SURPASS-ET (NCT04285086)
  • Phase: Global Phase 3
  • Patient population: Adults with high-risk ET and leukocytosis who were hydroxyurea-resistant or hydroxyurea-intolerant
  • Randomization: 174 patients randomized 1:1 to BESREMi (n=91) or anagrelide (n=83)
  • Comparator: Anagrelide
  • Treatment duration assessed: 12 months
  • Principal Investigator: Ruben Mesa, M.D., President of Advocate Health’s Cancer National Service Line (Atrium Health Levine Cancer Institute and Comprehensive Cancer Center at Atrium Health Wake Forest Baptist)

Endpoints

  • Primary endpoint: Durable modified European LeukemiaNet (ELN) response at both months 9 and 12, incorporating blood count remission, improvement or non-progression of splenomegaly and disease-related symptoms, and absence of hemorrhagic or thrombotic events
  • Secondary assessments: Included hematologic response, disease-related symptoms, splenomegaly, thromboembolic events, molecular response, and safety

Efficacy Outcomes

  • BESREMi demonstrated a higher durable modified ELN response rate at months 9 and 12, with responses observed in 37.4% of patients versus 3.6% with anagrelide in the FDA efficacy analysis.
  • BESREMi demonstrated durable hematologic and disease control across components of the modified ELN response criteria.
  • The SURPASS-ET study also demonstrated fewer thromboembolic events with BESREMi than with anagrelide over the study period.

Regulatory Context

  • This approval expands BESREMi’s existing FDA label, which was previously limited to adults with polycythemia vera (PV)
  • The approval represents the first new FDA-approved treatment for ET in nearly 30 years, with BESREMi expected to be commercially available in the United States immediately following the approval announcement.
  • BESREMi has also recently received regulatory approval in Japan and Taiwan for ET, broadening global access.

    • Key Clinical Implications

    ✔ BESREMi is now an FDA-approved option for treatment-naïve adults with ET, regardless of genotype, broadening clinician choice without requiring prior cytoreductive therapy exposure.

    ✔ BESREMi provides a long-acting interferon-based approach that targets underlying disease biology, offering the potential for disease control beyond platelet-count reduction alone.

    ✔ Fewer thromboembolic events were observed with BESREMi than with anagrelide in SURPASS-ET, an important finding given the thrombotic morbidity associated with ET, including risks of stroke, myocardial infarction, and pulmonary embolism.

    ✔ BESREMi is administered subcutaneously every 2 weeks for ET, with dose escalation from 250 mcg initially to 350 mcg at week 2 and a maintenance dose of 500 mcg beginning at week 4, unless dose modification is required for tolerability.

    ✔ BESREMi now carries FDA-approved indications for both ET and PV, expanding the role of ropeginterferon alfa-2b-njft across two major Philadelphia chromosome–negative myeloproliferative neoplasms.

    Bottom Line

    The FDA approval of BESREMi (ropeginterferon alfa-2b-njft) for adults with essential thrombocythemia represents the first new FDA-approved ET treatment in nearly three decades. Supported by Phase 3 SURPASS-ET data demonstrating superior durable modified ELN responses compared with anagrelide, BESREMi provides a new long-acting interferon-based treatment option for adults with ET regardless of genotype or prior treatment status. The approval expands therapeutic options beyond conventional cytoreduction and introduces an FDA-approved approach designed to target underlying disease biology while providing durable hematologic control.

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