Efficacy and safety of abatacept in biologic-naive patients with active rheumatoid arthritis by background methotrexate dose: post hoc analysis of a randomized, placebo-controlled, phase 4 study

Objectives The objective of this study is to evaluate efficacy and safety of abatacept in biologic-naive, anti-citrullinated protein antibody (ACPA)-positive Japanese patients with active rheumatoid arthritis (RA) by background methotrexate (MTX) dose. Methods In this post hoc analysis of a randomized, double-blind, placebo-controlled phase 4 study (NCT01758198), patients received intravenous abatacept (similar to 10 mg/kg) or placebo both with MTX (>= 6 mg/week). Efficacy (Disease Activity Score 28 using C-reactive protein [DAS28 (CRP)] and Health Assessment Questionnaire-Disability Index [HAQ-DI]) was assessed by baseline MTX dosage (<= 8 and >8 mg/week) to week 16; safety was assessed by MTX dosage <= 8 and >8 mg/week. Change from baseline in DAS28 (CRP) and HAQ-DI was assessed using longitudinal repeated measures analysis. Results Overall, 101 and 102 patients received abatacept + MTX <= 8 and >8 mg/week, while 96 and 106 patients received placebo + MTX <= 8 and >8 mg/week, respectively. Regardless of baseline MTX dose received, mean changes from baseline in DAS28 (CRP) and HAQ-DI in abatacept groups were similar; repeated measures analysis showed similar trends in changes from baseline in DAS28 (CRP) and HAQ-DI. Abatacept safety profile was consistent with previous observations. Conclusions Post hoc analysis demonstrated similar efficacy and safety of abatacept in biologic-naive ACPA-positive Japanese patients with RA regardless of baseline MTX dose.