Association Between Abatacept Exposure Levels and Infection Occurrence in Patients With Rheumatoid Arthritis: Post Hoc Analysis of the AVERT-2 Study.

Objective: To determine whether higher serum exposure during subcutaneous (SC) abatacept (ABA) treatment was associated with an increased infection risk in adult patients with early rheumatoid arthritis (RA).

Methods: Data from Assessing Very Early Rheumatoid Arthritis Treatment-2 (AVERT2; ClinicalTrials.gov: NCT02504268), a randomized, placebo-controlled study in anticitrullinated protein antibody-positive patients with early RA, were analyzed. A post hoc population pharmacokinetic (PPK) analysis was performed. The association between steady-state ABA concentration exposures (ie, steady-state time-averaged serum concentration, steady-state trough serum concentration, steady-state maximum serum concentration) and first infection was evaluated using Kaplan-Meier plots of probability vs time receiving treatment and Cox proportional hazards models.

Results: The PK model of SC ABA was defined as a linear 2-compartment model with first-order absorption and elimination, and higher body weight was the only covariate with a clinically relevant effect in the final PPK model. Infections occurred in 330/693 patients treated with ABA + methotrexate (MTX; 47.6%; 11/693 [1.6%] with serious infections) and 134/301 of those treated with ABA placebo + MTX (44.5%; 4/301 [1.3%] with serious infections). Exposure-response analysis demonstrated no exposure relationship for an increased risk of first infection for patients with concomitant use of MTX and glucocorticoids (GCs) during the induction period, baseline GC use, or higher-than-median body weight (> 70 kg) at baseline.

Conclusion: This exposure-response analysis of AVERT-2 showed no increase in the risk of first infection, regardless of ABA exposure level, in patients with RA treated with SC ABA. Similarly, no effect on the risk of first infection was found for concomitant MTX and GC use in patients with RA treated with SC ABA + MTX.