FDA approves orphan drug status for ruxolitinib

Issue: December 10, 2011

The FDA today announced the approval of ruxolitinib to treat the rare bone marrow disease myelofibrosis. The disease is caused by deregulation of the JAK1 and JAK2 enzymes.

Ruxolitinib (Jakafi, Incyte) has been designated as an orphan drug, meaning it address a disease that affects fewer than 200,000 people in the United States. The drug is a twice-daily oral inhibitor of JAK1 and JAK2, which are involved in regulating blood and immunological functioning.

In myelofibrosis, scar tissue replaces bone marrow, which results in organs such as the liver and the spleen taking over the production of blood cells. The disease is characterized by enlarged spleen, anemia and decreased production of white blood cells and platelets. Symptoms include fatigue, abdominal discomfort, pain under the ribs, satiety, muscle and bone pain, itching and night sweats.

The FDA based the approval on results from the COMFORT trials, which involved 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 required treatment due to disease-related symptoms.

Patients were assigned to ruxolitinib, placebo or best available therapy with hydroxyurea or glucocorticoids. Patients assigned to the experimental groups experienced a reduction in spleen size of more than 35% compared with patients receiving placebo or best available therapy. Similarly, a larger proportion of patients assigned to ruxolitinib experienced a more than 50% reduction in their myelofibrosis-related symptoms, including abdominal discomfort, night sweats, itching and bone or muscle pain, compared with placebo.

The most serious adverse effects observed with ruxolitinib include thrombocytopenia, anemia, fatigue, diarrhea, dyspnea, headache, dizziness and nausea.

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