First-time adverse drug reactions, survival analysis, and the share of adverse drug reactions in treatment discontinuation in real-world rheumatoid arthritis patients: a comparison of first-time treatment with adalimumab and etanercept.

Background: This study aims to compare nature and frequency of adverse drug reactions (ADRs), time to first ADR, drug survival, and the share of ADRs in treatment discontinuation of first-time treatment with adalimumab (ADA) and etanercept (ETN) in real-world RA patients.
Research Design and Methods: Retrospective, single-center cohort study including naïve patients treated between January 2003-April 2020. Time to first ADR and drug survival of first-time treatment were studied using Kaplan-Meier and Cox-regression models up to 10 years, with 2- and 5-year post-hoc sensitivity analysis. Nature and frequencies of first-time ADRs and causes of treatment discontinuation were assessed.
Results: In total, 416 patients (ADA: 255, ETN: 161, 4865 patient years) were included, of which 92 (22.1%) experienced ADR(s) (ADA: 59, 23.1%; ETN: 33, 20.4%). Adjusted for age, gender and concomitant conventional DMARD use, ADA was more likely to be discontinued than ETN up to 2-, 5- and 10-year follow-up (adjusted HRs 1.63; 1.62; 1.59 (all p<0.001)). ADRs were the second reason of treatment discontinuation (ADA 20.7%, ETN 21.4%).
Conclusions: Despite seemingly different nature and frequencies, ADRs are the second reason of treatment discontinuation for both bDMARDs. Furthermore, 2-, 5-, and 10-year drug survival is longer for ETN compared to ADA.