Objectives: This study aimed to evaluate if and how the incidence of serious infection (SI) and active tuberculosis (TB) differ among seven biological disease-modifying antirheumatic drugs (bDMARDs) in patients with rheumatoid arthritis (RA) considering the line of therapy.

Methods: Patients with RA from the British Society for Rheumatology Biologics Register-RA cohort who initiated etanercept, certolizumab, infliximab, adalimumab, abatacept, rituximab, or tocilizumab from the first to fifth line of therapy were included. Follow-up extended up to three years. Primary outcome was SI, secondary outcome was TB. Event rates were calculated and compared using Cox proportional-hazards, controlling for confounding with inverse probability of treatment weights. Comparisons were made overall and stratified by line of therapy. Sensitivity analysis restricted to all treatment courses from 2009 (tocilizumab availability) until end of study (2018).

Results: Among 33 897 treatment courses (62 513 patient-years) the incidence of SI was 4.4/100 patient-years (95%CI 4.2-4.5). After adjustment, hazards ratios (HR) of SI were slightly higher with adalimumab and infliximab compared with etanercept. However, no clear pattern was observed when stratifying by line of therapy, in terms of incidence rate or hazards ratio. Sensitivity analyses showed similar HR among these treatments. Regarding TB, all 49 cases occurred during the first three lines of treatment and rarely since 2009.

Conclusion: The risk of serious infections does not appear to be influenced by the line of therapy in patients with RA. However, the risk of tuberculosis seems to be more frequent during the initial lines of treatment or prior to 2009.