The Food and Drug Administration has approved the use of ruxolitinib (Jakafi, made by Incyte Corp.) for patients with myelofibrosis, the first such drug specifically approved for the disease.

The pill taken two times a day, inhibits JAK (Janus Associated Kinase) 1 and 2, which are involved in regulating blood and immunological functioning, and myelofibrosis is associated with their deregulation.

"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," Richard Pazdur, MD, Director of the FDA's Office of Hematology and Oncology Products in the Center for Drug Evaluation and Research, said in a statement. "The clinical trials leading to this approval focused on problems that patients with myelofibrosis commonly encounter, including enlarged spleens and pain."

"The FDA approval of Jakafi has the potential to transform the way we treat myelofibrosis," said Srdan Verstovsek, MD, PhD, Associate Professor in the Department of Leukemia at the University of Texas MD Anderson Cancer Center, the principal investigator of the COMFORT-I pivotal trial.

"In this Phase III clinical trial, we observed significant reductions in spleen size and significant improvements in symptoms. Importantly, these benefits were achieved early on, most within a month, and tended to be durable during treatment. In contrast, most of the patients who received placebo saw their spleens increase and their symptoms worsen."

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. All patients had 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, or the best available therapy (hydroxyurea or glucocorticoids). A greater percentage of patients receiving Jakafi experienced more than a 35% reduction in spleen size when compared with patients receiving placebo or best available therapy. Similarly, more patients receiving Jakafi had more than a 50% reduction in their myelofibrosis-related symptoms than was the case in patients receiving placebo.

The most serious side effects seen in patients treated with Jakafi were thrombocytopenia, anemia, fatigue, diarrhea, dyspnea, headache, dizziness, and nausea.

Jakafi was reviewed under the FDA's priority review program, and was approved ahead of the drug's December 3 review goal date under the Prescription Drug User Fee Act. Jakafi has been designated as an orphan drug, which identifies the disease as affecting fewer than 200,000 people in the United States.