FDA approves treatment for patients with rare bone marrow disorder

“Prior to today, there was one FDA-approved drug to treat patients with myelofibrosis, a rare bone marrow disorder. Our approval today provides another option for patients,” said Richard Pazdur, M.D., director of the FDA’s Oncology Center of Excellence and acting director of the Office of Hematology and Oncology Products in the FDA’s Center for Drug Evaluation and Research. “The FDA is committed to encouraging the development of treatments for patients with rare diseases and providing alternative options, as not all patients respond in the same way.”

Myelofibrosis is a chronic disorder where scar tissue forms in the bone marrow and the production of the blood cells moves from the bone marrow to the spleen and liver, causing organ enlargement. It can cause extreme fatigue, shortness of breath, pain below the ribs, fever, night sweats, itching and bone pain. When myelofibrosis occurs on its own, it is called primary myelofibrosis. Secondary myelofibrosis occurs when there is excessive red blood cell production (polycythemia vera) or excessive platelet production (essential thrombocythemia) that evolves into myelofibrosis.

Jakafi (ruxolitinib) was approved by the FDA in 2011. The approval of Inrebic for intermediate-2 or high-risk primary or secondary (post-polycythemia vera or post-essential thrombocythemia) myelofibrosis was based on the results of a clinical trial where 289 patients with myelofibrosis were randomized to receive two different doses (400 mg or 500 mg daily by mouth) of fedratinib or placebo. The clinical trial showed that 35 of 96 patients treated with the fedratinib 400 mg daily dose (the dose recommended in the approved label) experienced a significant therapeutic effect (measured by greater than or equal to a 35% reduction from baseline in spleen volume at the end of cycle 6 (week 24) as measured by an MRI or CT scan with a follow-up scan four weeks later). As a result of treatment with Inrebic, 36 patients experienced greater than or equal to a 50% reduction in myelofibrosis-related symptoms, such as night sweats, itching, abdominal discomfort, feeling full sooner than normal, pain under ribs on left side, and bone or muscle pain.

The prescribing information for Inrebic includes a Boxed Warning to advise health care professionals and patients about the risk of serious and fatal encephalopathy (brain damage or malfunction), including Wernicke’s, which is a neurologic emergency related to a deficiency in thiamine. Health care professionals are advised to assess thiamine levels in all patients prior to starting Inrebic, during treatment and as clinically indicated. If encephalopathy is suspected, Inrebic should be immediately discontinued.

Common side effects for patients taking Inrebic are diarrhea, nausea, vomiting, fatigue and muscle spasms. Health care professionals are cautioned that patients may experience severe anemia (low iron levels) and thrombocytopenia (low level of platelets in the blood). Patients should be monitored for gastrointestinal toxicity and for hepatic toxicity (liver damage). The dose should be reduced or stopped if a patient develops severe diarrhea, nausea or vomiting. Treatment with anti-diarrhea medications may be recommended. Patients may develop high levels of amylase and lipase in their blood and should be managed by dose reduction or stopping the mediation. Inrebic must be dispensed with a patient Medication Guide that describes important information about the drug’s uses and risks.

The FDA granted this application Priority Review designation. Inrebic also received Orphan Drug designation, which provides incentives to assist and encourage the development of drugs for rare diseases. The FDA granted the approval of Inrebic to Impact Biomedicines, Inc., a wholly-owned subsidiary of Celgene Corporation.

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