The  U.S. Food and Drug Administration (FDA) has accepted for filing the supplemental New Drug Application (sNDA) for Jakafi® (ruxolitinib) as a potential treatment of patients with polycythemia vera (PV) who have had an inadequate response to or are intolerant of hydroxyurea.

PV is a myeloproliferative neoplasm (MPN) characterized by an overproduction of normal red blood cells, white blood cells and platelets that leads to an increased risk of thrombosis.  PV may occur at any age but often presents later in life, with a median age at diagnosis of 60 years.

Untreated, PV can lead to a thickening of the blood and, eventually, heart attack and stroke. Phlebotomy is one treatment deployed in which blood is removed from the body. In addition, the drug, hydroxyurea, is sometimes used to reduce an enlarged spleen, which is also associated with PV.  Approximately 100,000 patients in the United States are living with PV and approximately 25 percent of patients with PV develop resistance to or intolerance of hydroxyurea.

Jakafi is the first and only FDA-approved treatment for patients with intermediate or high-risk myelofibrosis (MF), including primary MF, post–PV MF and post–essential thrombocythemia MF. Jakafi is also the first JAK1/JAK2 inhibitor to demonstrate efficacy in a Phase III trial in patients with PV and will be the first JAK1/JAK2 inhibitor made available to patients with PV in the U.S.

In a randomized phase 3 study of PV patients, researchers determined that Jakafi was well tolerated and better controlled hematocrit ratios (ratio of red blood cell volume to total blood volume) than did the best available therapy. Jakafi was also successful in reducing spleen volume and improving PV symptoms.

Researchers in this study enrolled PV patients who were phlebotomy dependent and intolerant or resistant to hydroxyurea. Patients were randomized to Jakafi (110 patients) or the best available therapy (BAT, 112 patients).  The primary endpoint of the study was the proportion of patients who reached hematocrit control without phlebotomy and a greater than 35% reduction in spleen volume. This endpoint was reached by 21% of the Jakafi cohort, while only 1% of the BAT patients reached it. At 48 weeks, 91% of the Jakafi group had maintained their response.

Sixty percent of the Jakafi cohort and 20% of the BAT group achieved hematocrit control without phlebotomy. Thirty-eight percent of the Jakafi  group and 1% of the BAT group achieved the spleen volume reduction goal.  Complete hematological response at week 32 was seen in 24% and 9% of Jakafi and BAT patients, respectively.

Researchers concluded that Jakafi was well tolerated and improved patients’ ability to control hematocrit levels without phlebotomy, as well as reduced spleen volume.

Reference: Verstovsek, Srdan et al. Results of a prospective, randomized, open-label phase 3 study of ruxolitinib in polycythemia vera patients resistant to or intolerant of hydroxyurea: the RESPONSE trial. J Clin Oncol 32:5s, 2014 (suppl; abstr 7026).

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