Efficacy and safety of ruxolitinib and hydroxyurea combination in patients with hyperproliferative myelofibrosis.

Ruxolitinib is the only commercially available JAK1/2 inhibitor approved for the treatment of myelofibrosis-related splenomegaly and symptoms. During treatment, as rare conditions, leukocytosis and/or thrombocytosis could develop and the management of these situations is not well established. We report here 53 myelofibrosis patients that received a combination of hydroxyurea and ruxolitinib because of uncontrolled myeloproliferation. Both drugs were administered outside clinical trials. At 48 weeks, a significant reduction in leucocyte and platelet counts was observed (p = 0.02 and p = 0.04, respectively). Additionally, the spleen volume decreased from a median value of 10 cm below the left costal margin (range, 0-10) to 6 cm (range, 0-15). The rate of spleen response increased from 14% at the start of the combination to 45% after 48 weeks. The safety profile of the combination was consistent with that observed with ruxolitinib single agent. These data require further confirmation in large cohorts of patients prospectively assessed.