Long-Term Survival Of Subcutaneous Biosimilar TNFα Inhibitors Compared To Originators: Results From A Multicenter Prospective Registry.

OBJECTIVE:To analyze the long-term survival of subcutaneous biosimilar TNFα-inhibitors (TNFi) compared to the originator molecules in patients with rheumatic diseases, and the factors associated with drug discontinuation. METHODS:Retrospective analysis of BIOBADASER, the Spanish multicenter prospective registry of rheumatic patients on biological and targeted disease-modifying anti-rheumatic drugs. Patients who started etanercept or adalimumab from January 2016 to October 2023 were included. The survival probabilities of biosimilars and originators were compared using Kaplan-Meier estimating curves. To identify factors associated with differences in the retention rates, hazard ratios (HR) were estimated using Cox regression models for all and specific (inefficacy or adverse events) causes of discontinuation. RESULTS:A total of 4162 patients received 4723 treatment courses (2991 courses of adalimumab and 1732 courses of etanercept), of which 722 (15.29%) were originator molecules and 4001 (84.71%) biosimilars. The originators were more frequently discontinued than biosimilars (53.32% and 33.37%, respectively). The main reason for discontinuation was inefficacy (60.35% of the treatments). The risk of overall discontinuation was lower for biosimilars (adjusted HR 0.84, 95% CI: 0.75-0.95). Female sex, obesity and second or later treatment lines increased the risk of discontinuation, while disease duration and the use of concomitant methotrexate were associated to a greater survival. When assessing cause-specific reasons of discontinuation, excluding nonmedical switching, the results from the crude and adjusted analyses showed no significant differences in the retention rate between biosimilars and originators. CONCLUSION:No significant differences were found between treatmens in the longterm survival due to inefficacy or adverse events.