by Dr. C. H. Weaver M.D. updated 12/2018
Clinical trials, the most recent of which was presented at the 23rd Congress of the European Hematology Association (EHA) in Stockholm, Sweden evaluating Jakafi (ruxolitinib) in individuals with myelofibrosis (MF) and Polycythema Vera (PV) have reported that treatment can reduce spleen size and it associated symptoms, as well as provide better control of the hematocrit.(1,2,3)
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.
Individuals with MF and PV may experience pain or fullness under their ribs on the left side of their body. This may occur because of enlargement of their spleen. The spleen is an organ that helps the body fight infection and filter unwanted material, such as old or damaged blood cells. The increased number of blood cells caused by MF and PV may make the spleen work harder causing the spleen to get bigger, a condition referred to as spleenomegaly.
Jakafi is a first-in-class JAK1/JAK2 inhibitor approved by the U.S. Food and Drug Administration for treatment of people with PV who have had an inadequate response to or are intolerant of hydroxyurea. Jakafi is also indicated for treatment of people with intermediate or high-risk myelofibrosis, including primary MF, post–polycythemia vera MF, and post–essential thrombocythemia MF.
In one 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.
- 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).
- Guglielmelli, et al. Safety and Efficacy of Ruxolitinib (Rux) in Patients (Pts) with Dipss Low-Risk Myelofibrosis (MF) in the Phase 3b Expanded-Access Jump Study. EHA 2018. Abstract PF623.
- Gupta, et al. Predictors of Response to Ruxolitinib (Rux) in Patients (Pts) with Myelofibrosis (MF) in the Phase 3b Expanded-Access Jump Study. EHA 2018. Abstract PF616.
- Vannucchi, et al. Results from 48-week follow-up of the EXPAND study: a phase 1b, open-label, dose-finding study of ruxolitinib in patients with myelofibrosis and low platelet counts (50-99 × 109/L) at baseline. EHA 2018. Abstract PF611.
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