The U.S. Food and Drug Administration (FDA) has approved fedratinib to treat intermediate-2 or high-risk primary or secondary (post-polycythemia vera or post-essential thrombocythemia) myelofibrosis. This decision makes fedratinib only the second FDA-approved drug to treat the rare bone marrow disorder, following ruxolitinib’s approval in 2011.
The FDA granted fedratinib priority review designation based on results from a clinical trial in which 289 patients with myelofibrosis were randomly assigned to receive either 400 mg or 500 mg of fedratinib or placebo. Thirty-five of the 96 patients who received fedratinib 400 mg once-daily experienced a ≥35% reduction in baseline spleen volume after 24 weeks of treatment. Thirty-six patients experienced a ≥50% reduction in symptoms related to their disease, such as night sweats, itching, feeling full quickly, abdominal discomfort, and bone or muscle pain.
The most common adverse events associated with fedratinib included diarrhea, nausea, vomiting, fatigue, and muscle spasms. In its approval, the FDA noted that patients may experience severe anemia and thrombocytopenia and should be monitored for hepatic and gastrointestinal toxicity.
Fedratinib was approved with a boxed warning advising health care professionals and patients about the risk of encephalopathy, including Wernicke encephalopathy. The prescribing information instructs health care professionals to assess thiamine levels in all patients prior to starting treatment, during treatment, and as clinically indicated, as low levels are also associated with the encephalopathy.