Comparative Effectiveness and Persistence of SB4 and Reference Etanercept in Patients With Psoriatic Arthritis in Norway

Objective. We aim to compare drug effectiveness and persistence between the reference etanercept (ETN) and ETN biosimilar SB4 in patients with psoriatic arthritis (PsA) naive to ETN and to investigate drug effectiveness and persistence in those undergoing a mandatory nonmedical switch from ETN to SB4. Methods. We used a retrospective comparative database study including 1,138 patients with PsA treated with ETN or SB4 (years 1999-2021) in Norway. Disease activity score in 28 joints (DAS28) and drug persistence were compared between unmatched ETN (n = 644) and SB4 (n = 252) cohorts and in matched analyses (n = 144, both cohorts) at baseline using a propensity score (PS) to adjust for confounders. Drug persistence was analyzed with the Kaplan-Meier method. Results. In unmatched analyses, difference in change from baseline between ETN (n = 140) and SB4 (n = 132) for DAS28 at one year was mean 0.67 (95% confidence interval [CI] 0.38-0.96) in favor of ETN. In PS-matched analyses, the difference in change from baseline between ETN (n = 54) and SB4 (n = 54) was mean 0.09 (95% CI -0.33 to 0.50), and the mean difference assessed with an analysis of covariance model was 0.01 (95% CI -0.38 to 0.40), both within predefined equivalence margin (+/- 0.6). Drug persistence at one year was mean 0.75 (95% CI 0.71-0.78) for ETN, mean 0.58 (95% CI 0.51-0.63) for SB4, hazard ratio (HR) 2.45 (95% CI 2.02-2.97) in unmatched analysis, and mean 0.55 (95% CI 0.46-0.63) for ETN, mean 0.60 (95% CI 0.51-0.67) for SB4, HR 1.29 (95%CI 0.94-1.76) in PS-matched cohorts. Conclusion. At one year, outcomes for PsA disease activity and drug persistence were comparable for patients treated with either ETN or SB4. In patients undergoing a mandatory nonmedical switch from ETN to SB4, drug effectiveness was maintained during a two-year period.