Retrospective analysis of eltrombopag for the treatment of refractory primary immune thrombocytopenia in Japan.

Eltrombopag, an oral thrombopoietin receptor agonist, is a novel drug that can be used in cases with previously-treated primary immune thrombocytopenia (ITP). In this study, we retrospectively analyzed 22 Japanese ITP patients treated in four hospitals. A responder was defined as a patient achieving a platelet count between 50,000/μl and 400,000/μl, at 75% or more of on-treatment assessments. Excluding 2 patients whose treatments were interrupted at their request, 13 of 20 patients (65%) were responders. Ten of the 13 responders had been taking more than 5 mg of a steroid preparation in the form of prednisolone or its equivalent. In 7 of these patients, the steroid dose could be tapered to 5 mg or less. Disappearance or amelioration of hemorrhagic symptoms was observed in 11 of 19 patients who had these symptoms prior to treatment (9 of 10 responders, 2 of 7 non-responders), and the improvement rate was greater in responders (p=0.018). No factors were identified as being related to efficacy. Reported adverse effects were fever (1), malaise (3), headache (2), and muscle pain (1). One severe adverse event, cerebral thromboembolism, was reported in 1 patient. Although eltrombopag is a useful therapeutic agent for refractory ITP, it is necessary to evaluate its position in the overall treatment strategy for ITP after assessing long-term complications as well as therapeutic effects.