Immunogenicity, safety, and efficacy of abatacept administered subcutaneously with or without background methotrexate in patients with rheumatoid arthritis: results from a phase III, international, multicenter, parallel-arm, open-label study.

OBJECTIVE: To evaluate the impact of concomitant methotrexate (MTX) on subcutaneous (SC) abatacept immunogenicity, and to assess safety and efficacy. METHODS: This phase III, open-label study had a 4-month short-term (ST) period and an ongoing long-term extension (LTE) period. Rheumatoid arthritis patients were stratified to receive SC abatacept (125 mg/week) with (combination) or without MTX (monotherapy), with no intravenous loading dose; patients receiving monotherapy could add MTX in the LTE period. Immunogenicity (percentage of anti-abatacept antibody-positive patients) was assessed. ST and LTE period data are reported, including efficacy through LTE month 14 and safety through LTE month 20. RESULTS: Ninety-six of 100 enrolled patients completed the ST period; 3.9% (combination) and 4.1% of patients (monotherapy) developed transient immunogenicity, and no patients were antibody positive at month 4. Serious adverse events (SAEs) were reported in 3.9% (combination) and 6.1% of patients (monotherapy); 5.9% (combination) and 8.2% of patients (monotherapy) experienced SC injection reactions, and all were mild in intensity. Mean 28-joint Disease Activity Score (DAS28) changes were -1.67 (95% confidence interval [95% CI] -2.06, -1.28; combination) and -1.94 (95% CI -2.46, -1.42; monotherapy) at month 4. Ninety patients entered and were treated in the LTE period; 83.3% (75 of 90) remained ongoing at month 24. One LTE-treated patient (1.1%) developed immunogenicity, 14.4% of patients experienced SAEs, and no SC injection reactions were reported. For patients entering the LTE period, mean DAS28 changes from baseline were -1.84 (95% CI -2.23, -1.34; combination) and -2.86 (95% CI -3.46, -2.27; monotherapy) at month 18. CONCLUSION: SC abatacept did not elicit immunogenicity associated with loss of safety or efficacy, either with or without MTX.

Clinical response and tolerability to abatacept in patients with rheumatoid arthritis previously treated with infliximab or abatacept: open-label extension of the ATTEST Study.

OBJECTIVE: To assess the efficacy and safety of abatacept in biological-naive patients with rheumatoid arthritis and an inadequate response to methotrexate treated in the long-term extension (LTE) of the ATTEST trial. METHODS: Patients randomly assigned to abatacept, placebo or infliximab completing the 1-year double-blind period were eligible to receive abatacept ∼10 mg/kg in the open-label LTE. Efficacy to year 2 is presented for patients randomly assigned to abatacept or infliximab who switched to open-label abatacept. Safety data are presented for all patients entering LTE regardless of double-blind treatment. RESULTS: Of 431 patients randomly assigned, 79.8% remained on abatacept at year 2. At years 1 and 2, 19.7% and 26.1% of abatacept and 13.3% and 28.6% of infliximab-to-abatacept patients achieved disease activity score 28-defined remission (<2.6). Safety with abatacept during the cumulative study period was consistent with the double-blind experience, with no increase in adverse event incidence following the switch to abatacept. CONCLUSION: In methotrexate-inadequate responders, abatacept efficacy was maintained over 2 years. For infliximab-to-abatacept patients, efficacy improvements were seen in year 2 after patients switched to abatacept. Switching directly from infliximab to abatacept was well tolerated. These data demonstrate that abatacept provides sustained responses and consistent safety, suggesting that switching from infliximab to abatacept is a viable treatment option.