Objectives. To examine the long-term safety of intravenous (IV) abatacept treatment in Japanese patients with rheumatoid arthritis (RA) and an inadequate response to methotrexate (MTX) or other conventional or biologic disease-modifying antirheumatic drugs. Methods. This Phase III, open-label, long-term study (NCT00484289) comprised Japanese patients with RA who had completed abatacept Phase I or Phase II studies, and new patients intolerant to MTX. Patients from Phase I and Phase II studies received a weight-tiered dosing equivalent of 10 mg/kg abatacept, with MTX at doses up to 8 mg/week; newly enrolled patients received weight-tiered 10 mg/kg abatacept monotherapy. Safety and efficacy were assessed. Results. A total of 217 patients (Phase I, n = 13; Phase II, n = 178; newly enrolled, n = 26) were treated with IV abatacept for a mean of 3 years. Serious adverse events occurred in 67/217 (30.9%) patients. Most adverse events were mild or moderate. For all cohorts combined, American College of Rheumatology 20% response rates ranged from 61.3 to 81.8% for as-observed and last observation carried forward analyses over 192 weeks. Following initial response, clinical and functional outcomes were maintained for up to 3 years. Conclusions. In Japanese patients with RA, IV abatacept with and without background MTX showed tolerable safety and sustained efficacy over 3 years.
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