In a randomized phase 3 study of polycythemia vera (PV) patients, researchers determined that Jakafi® (ruxolitinib) 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.

PV is a blood disease in which the body makes too many red blood cells. This 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.

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 ruxolitinib 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 ruxolitinib 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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