Jakafi: First Drug Approved for Treatment of Polycythemia Vera
The U.S. Food and Drug Administration today approved a new use for Jakafi (ruxolitinib) to treat patients with polycythemia vera, a chronic type of bone marrow disease. Jakafi is the first drug approved by the FDA for this condition.
Polycythemia vera occurs when too many red blood cells are made in the bone marrow. Patients may also experience an increase in white blood cells and platelets. An overabundance of blood cells can cause the spleen to swell, bleeding problems and blood clots in the veins near the skin surface (phlebitis). In addition, it puts patients at increased risk of stroke or heart attack.
Jakafi’s new use is intended to treat polycythemia vera patients who have an inadequate response to or cannot tolerate hydroxyurea, another medicine often prescribed to reduce the number of red blood cells and platelets in the blood. Jakafi works by inhibiting enzymes called Janus Associated Kinase (JAK) 1 and 2 that are involved in regulating blood and immunological functioning. The drug’s approval to treat polycythemia vera will help decrease the occurrence of an enlarged spleen (splenomegaly) and the need for phlebotomy, a procedure to remove excess blood from the body.
“The approval of Jakafi for polycythemia vera underscores the importance of developing drugs matched to our increasing knowledge of the mechanisms of diseases,” 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 trial used to evaluate Jakafi confirmed clinically meaningful reductions in spleen size and the need for phlebotomies to control the disease.”
Jakafi’s safety and effectiveness to treat polycythemia vera were evaluated in a clinical study involving 222 participants who had the disease for at least 24 weeks, had an inadequate response to or could not tolerate hydroxyurea, had undergone a phlebotomy procedure and exhibited an enlarged spleen. Participants were randomly assigned to receive Jakafi or the best available therapy, as determined by the investigator on a participant-by-participant basis.
The study was designed to measure the reduced need for phlebotomy beginning at Week 8 and continuing through Week 32, in addition to at least 35 percent reduction in spleen volume at Week 32. Results showed 21 percent of Jakafi-treated participants experienced a reduction in the need for a phlebotomy and a reduction in spleen volume, compared to 1 percent of participants who received best available therapy.
The most common side effects associated with use of Jakafi in participants with polycythemia vera were low red blood cell counts (anemia) and low blood platelet counts (thrombocytopenia). The most common non-blood related side effects were dizziness, constipation and shingles.
The FDA reviewedJakafi’s use for polycythemia vera under the agency’s priority review program because, at the time the application was submitted, the drug demonstrated the potential to be a significant improvement in safety or effectiveness over available therapy in the treatment of a serious condition. Priority review provides an expedited review of a drug’s application. Jakafi also received orphan product designation because it is intended to treat a rare disease.
In 2011, the FDA approved Jakafi for treatment of patients with another bone marrow disorder, intermediate or high-risk myelofibrosis, including primary myelofibrosis, post-polycythemia vera myelofibrosis and post-essential thrombocythemia myelofibrosis.
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