Myelofibrosis is a disease in which the bone marrow is replaced by scar tissue resulting in blood cells being made in organs such as the liver and the spleen. This disease is marked by an enlarged spleen, anemia, decreased white blood cells and platelets, and myelofibrosis-related symptoms.
Symptoms include fatigue, abdominal discomfort, pain under the ribs, feeling full (satiety), muscle and bone pain, itching, and night sweats.
Jakafi, a pill taken two times a day, inhibits enzymes called JAK 1 and 2 (Janus Associated Kinase) that are involved in regulating blood and immunological functioning. Myelofibrosis is associated with the deregulation of JAK 1 and 2.
“Jakafi represents another example of an increasing trend in oncology where a detailed scientific understanding of the mechanisms of a disease allows a drug to be directed toward specific molecular pathways,” said Richard Pazdur, M.D., director of the Office of Hematology and Oncology Products in the FDA’s Center for Drug Evaluation and Research. “The clinical trials leading to this approval focused on problems that patients with myelofibrosis commonly encounter, including enlarged spleens and pain.”
The safety and effectiveness of Jakafi was evaluated in two clinical trials with 528 patients. Patients in both trials were resistant or refractory to available myelofibrosis therapy or ineligible for allogeneic bone marrow transplantation (procedure where a person receives blood-forming stem cells from a genetically similar, but not necessarily identical, donor). All patients had enlarged spleens (splenomegaly) and were in need of treatment as a result of disease-related symptoms.
Patients in the studies were selected to receive treatment with either Jakafi, placebo (sugar pill) or the best available therapy (hydroxyurea, a chemotherapy agent, or glucocorticoids). A greater percentage of patients receiving Jakafi experienced more than a 35 percent reduction in spleen size when compared to patients receiving placebo or best available therapy. Similarly, a greater proportion of patients receiving Jakafi saw more than a 50 percent reduction in their myelofibrosis-related symptoms, including abdominal discomfort, night sweats, itching and bone or muscle pain, than was the case in patients receiving placebo.
The most serious side effects seen in patients treated with Jakafi include low blood platelet levels (thrombocytopenia), anemia, fatigue, diarrhea, shortness of breath (dyspnea), headache, dizziness, nausea, and confusion.
Jakafi was reviewed under the FDA’s priority review program, an expedited six-month review of drugs that may offer significant advances in treatment over available therapy or that provide a treatment when no adequate therapy exists.
The treatment is being approved ahead of the drug’s Dec. 3, 2011 review goal date under the Prescription Drug User Fee Act and has been designated as an orphan drug, which identifies the disease as affecting fewer than 200,000 people in the U.S.
Jakafi is manufactured by Incyte Corp. of Wilmington, Del.
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