Background: Eltrombopag is an oral, non-peptide thrombopoietin receptor agonist that has shown efficacy and safety in chronic immune thrombocytopenia (ITP). However, ethnic differences in eltrombopag exposure have been reported: area under the curve exposure to eltrombopag was 87% greater among ITP patients of East Asian descent than among ITP patients of non-East Asian ITP descent. Objectives: To evaluate the efficacy and safety of eltrombopag by using, in Japanese ITP patients, lower starting (12.5mg) and maximum (50mg) doses of eltrombopag than the standard starting (50mg) and maximum (75mg) doses approved in the USA and Europe. Patients: We examined 23 Japanese patients with previously treated chronic ITP with a platelet count of <30000μL -1 in a multicenter study comprising a randomized, double-blind, placebo-controlled phase for 6-week evaluation (15 eltrombopag, and eight placebo) and an open-label phase for 6-month evaluation (23 eltrombopag). Results and Conclusions: The response rate (platelet count of ≥50000μL -1) at week 6 of the 6-week double-blind phase was 60% in eltrombopag-treated patients and 0% in placebo-treated patients. Ten of 23 patients (43.5%) responded for ≥75% of predefined assessment visits during the 6-month open-label phase. Notably, 22% (5/23) of patients responded to 12.5mg of eltrombopag, which was administered within the first 3 weeks of eltrombopag treatment. Bleeding decreased with eltrombopag treatment as compared with baseline. Eltrombopag was generally well tolerated; one patient experienced a transient ischemic attack on day 9. Eltrombopag (12.5-50mg) is effective for the management of Japanese patients with chronic ITP (NCT00540423).
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