Search

Ruxolitinib (INC424), a potent and selective oral Janus kinase 1 and 2 inhibitor, was recently approved by the US food and drug administration for the treatment of intermediate or high-risk myelofibrosis. The safety, tolerability, and pharmacokinetics (PK) of ruxolitinib have been extensively evaluated in healthy subjects and patients. The present study is the first to investigate the PK and tolerability of ruxolitinib in the Japanese population. Forty subjects were randomized to receive single (10-100 mg) and multiple (10 and 25 mg every 12 h) doses of ruxolitinib or placebo. Cohorts were sequentially enrolled based on the outcome of safety assessments. Ruxolitinib was rapidly absorbed, and its exposure increased dose proportionally up to 100 mg. The half-life of ruxolitinib was approximately 3 h, and drug accumulation was not observed after repeated dosing at a 12-h dosing interval. Decreasing absolute neutrophil counts were observed in five Japanese subjects treated once (100 mg, n = 1) or twice (10 mg, n = 3; 25 mg, n = 1) daily. These events were manageable and reversible upon drug discontinuation. Orally administered ruxolitinib was well tolerated in healthy Japanese volunteers. There were no apparent differences in the safety or PK of ruxolitinib between Japanese and non-Japanese subjects.

We conducted the first nationwide survey to clarify the clinical features, treatment methods, and prognoses for polycythemia vera (PV) and essential thrombocythemia (ET). A 1-page questionnaire was mailed to members of the Japanese Elderly Leukemia and Lymphoma Study Group (JELLSG). Surveys on 647 patients (PV, 266 patients; ET, 381 patients) were returned and analyzed. Thrombotic events at diagnosis and during follow-up occurred at rates of 15.4% and 8.5%, respectively, in PV cases and 17.6% and 8.7% in ET cases. Splenomegaly was observed in only 28.8% of PV patients and 10.8% of ET patients. The leukocyte alkaline phosphatase score was elevated in only 46.2% of PV patients. The incidences of abnormal karyotypes were less than 10% in both PV and ET cases. The rates of transformation to myelofibrosis were 2.6% in both PV and ET cases, and acute leukemia was noted in 1.1% of PV patients and 2.9% of ET patients. Prognostic factors were thrombotic history for PV and thrombotic history and age (>or=60 years) for ET. The present study clearly demonstrated clinical differences between Japanese and Western patients for PV and ET. Concerning the treatment of PV and ET, the study revealed considerable variation among Japanese hematologists. These results suggest the necessity of developing treatment guidelines according to risk stratification that are suitable for Japanese PV and ET patients.