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The FDA granted a first-ever approval of an interferon for the rare blood disorder polycythemia vera (PV), also making ropeginterferon alfa-2b-njft (Besremi) the first approved PV therapy that patients can receive regardless of treatment history.

PV originates from a genetic mutation in stem cells in the bone marrow, leading to overproduction of blood cells. The condition predisposes a patient to blood clots, stroke, and heart attack, and can progress to myelofibrosis and blood cancers, including acute myeloid leukemia. Ropeginterferon alfa-2b binds to interferon alfa/beta receptors to set in motion a series of reactions that result in reduced blood cell production in the bone marrow.

"The FDA approval ... represents the next step in advancing patient care as it provides a critical addition to managing not only symptom burden and near-term complications but also the cancer early, which may help reduce the risk of disease progression over time," said Srdan Verstovsek, MD, PhD, of the University of Texas MD Anderson Cancer Center in Houston, in a from drug developer PharmaEssentia. "With the availability of an FDA-approved, next-generation interferon for this indication, it's time that we focus on preserving the long-term health of patients with polycythemia vera."

The approval also "highlights the FDA's commitment to helping make new treatments available to patients with rare diseases," said Ann Farrell, MD, of the agency's Center for Drug Evaluation and Research, in a .

More than 7,000 rare diseases affect more than 30 million people in the U.S., Farrell noted, including 6,200 new cases of PV each year.

Support for the approval came from a involving 51 patients with previously treated PV. The patients received the pegylated long-acting interferon for 7.5 years, and 61% of the study population attained complete hematologic response, defined as hematocrit <45% without phlebotomy, platelet count ≤400 × 10⁹/L, leukocytes ≤10 × 10⁹/L, and normal spleen size.

The rate of hematologic response increased to 80% when assessed by objective laboratory parameters only, excluding spleen size and thrombosis. Treatment decisions for patients with PV are most often based on laboratory criteria.

The most common adverse events (AEs) during the study were influenza-like illness, arthralgia, fatigue, pruritis, nasopharyngitis, and musculoskeletal pain. The most common serious AEs were urinary tract infection, transient ischemic attack, and depression. The FDA required a boxed warning on the risk of fatal or life-threatening neuropsychiatric, autoimmune, ischemic, and infectious disorders associated with ropeginterferon-alfa-2b.

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