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Abstract

METHODS: This open-label, Phase III study had a 4-month short-term (ST) period and ongoing long-term extension (LTE). RA patients were stratified to receive SC abatacept (125 mg/week) with (combination) or without (monotherapy) MTX, with no intravenous (IV) loading dose; monotherapy patients could add MTX in the LTE. Immunogenicity (% of anti-abatacept antibody-positive patients) was assessed; ST period and LTE data are reported: efficacy through LTE Month 14; safety through LTE Month 20.

RESULTS: 96/100 enrolled patients completed the ST period; 3.9% (combination) and 4.1% (monotherapy) of patients 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% (monotherapy) of patients; 5.9% (combination) and 8.2% (monotherapy) of patients experienced SC injection reactions, all were mild in intensity. Mean (95% confidence interval [CI]) 28-joint Disease Activity Score (DAS28) change was -1.67 (-2.06, -1.28; combination) and -1.94 (-2.46, -1.42; monotherapy) at Month 4. Ninety patients entered and were treated in the LTE; 83.3% (75/90) remained ongoing at Month 24. One LTE-treated patient (1.1%) developed immunogenicity; 14.4% of patients experienced SAEs; no SC injection reactions were reported. For patients entering the LTE, mean (95% CI) DAS28 change from baseline was -1.84 (-2.23, -1.34; combination) and -2.86 (-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.