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Abstract

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.