Safety and Efficacy of the Selective Costimulation Modulator Abatacept in Patients with Rheumatoid Arthritis Receiving Background Methotrexate: A 5-year Extended Phase IIB Study

Objective. To evaluate the safety and efficacy of abatacept plus methotrexate (MTX) over 5 years in patients with rheumatoid arthritis. Methods. Patients were randomized to abatacept 10 or 2 mg/kg or placebo, plus MTX. Patients completing the 1-year, double-blind period entered the longterm extension, where all patients received a fixed dose of abatacept similar to 10 mg/kg. We describe safety analyses for all patients who received at least I dose of abatacept and efficacy analyses for the original similar to 10 mg/kg abatacept-treated group, over 5 years. Results. Of the 235 abatacept- or placebo-treated patients completing the double-blind period, 219 entered the longterm extension; 130 (59.4%) were continuing at Year 5. No unexpected safety events were observed during the long-term extension compared with the double-blind period. Incidence rates of adverse events (AE) and Serious AE were 489.7 and 20.0/100 patient-years in Year I versus 374.9 and 18.9/100 patient-years in the cumulative period, respectively. Using exploratory analyses, improvements observed Lit Year I in the 10 mg/kg group were maintained at Year 5, as assessed by ACR responses (ACR20 = 77.1% vs 82.7%; ACR50 = 53.0% vs 65.4%; ACR70 = 28.9% vs 40.4% at Years I and 5, respectively) and disease activity (Low, Disease Activity State = 48.2% vs 58.5%; Disease Activity Score-28-defined remission = 25.3% vs 45.3% at Years I and 5, respectively). Conclusion. Abatacept maintained the efficacy observed at Year I over 5 years of treatment, and demonstrated consistent safety and tolerability. These data, along with relatively high retention rates, support the longterm clinical benefit provided by selective T cell costimulation modulation. Clinical trial registry: ClinicalTrials.gov; clinical trial registration number: NCT00254293. (First Release March 1 2009; J Rheumatol 2009;36:736-42; doi: 10.3899/jrheum.080813)