Infectious risk of add-on leflunomide or tacrolimus versus TNF inhibitors among patients with rheumatoid arthritis receiving background methotrexate: A population-based cohort study.

ABSTRACT

BACKGROUND: To compare infectious risk between leflunomide versus TNF inhibitors (TNFi), and between tacrolimus versus TNFi among rheumatoid arthritis (RA) patients receiving methotrexate (MTX). METHODS: Using Korea National Health Insurance Service database, we conducted a cohort study on RA patients initiating TNFi, leflunomide, or tacrolimus. The primary outcome was any serious infections defined as a composite endpoint of serious bacterial, opportunistic, and herpes zoster infections. Secondary outcomes were individual components of the primary outcome. Propensity-score fine-stratification (PSS) and weighting were applied to adjust for confounding. Hazard ratios (HRs) and 95% confidence intervals (CIs) were estimated using Cox proportional hazard models comparing leflunomide versus TNFi, and tacrolimus versus TNFi. RESULTS: Among 72,516 RA patients receiving MTX, we identified 3,336 TNFi initiators, 11,122 leflunomide initiators, and 5,136 tacrolimus initiators. Two study cohorts were 10,992 leflunomide initiators PSS-weighted on 1,623 TNFi initiators and 5,126 tacrolimus initiators PSS-weighted on 2,521 TNFi initiators. The incidence rate per 100 person-years of herpes zoster infection (3.70-4.27) was beyond 3-times that of serious bacterial infection (1.12-1.36), but opportunistic infection was relatively rare (0.11-0.23). The PSS-weighted HR [95% CI] for any serious infection was 1.03 [0.89-1.22] comparing leflunomide versus TNFi, and 0.91 [0.77-1.08] comparing tacrolimus versus TNFi. Analyses on the secondary outcomes showed consistent results. CONCLUSION: In this nation-wide cohort study, we did not find a significant difference in the risk of serious infections (i.e., serious bacterial, opportunistic, and herpes zoster infections) between leflunomide versus TNFi, and between tacrolimus versus TNFi among RA patients receiving background MTX.