To evaluate the effects of non-mandatory transitioning from the originator biologic drug etanercept (ETN) to its biosimilar, SB4, on drug survival and effectiveness in a controlled cohort study of patients with an inflammatory rheumatic disease.
In 2016, 642 patients were asked to transition their treatment from originator ETN to biosimilar SB4 by a structured communication strategy with opt-out option. Patients who consented to switch to SB4 were considered eligible for inclusion in the transition cohort, while patients being treated with originator ETN in 2014 were recruited as the historical cohort. Drug survival was compared between the 2 cohorts using Cox regression analyses, which were adjusted for age, sex, diagnosis, ETN treatment duration, ETN dose interval, conventional synthetic disease-modifying antirheumatic drug usage, and C-reactive protein (CRP) level, with a robust variance estimator applied to account for repeated subjects (i.e., patients who were included in both the transition cohort and the historical cohort). Adjusted differences in the 6-month change in CRP level, Disease Activity Score in 28 joints using CRP level (DAS28-CRP), and Bath Ankylosing Spondylitis Disease Activity Index were also assessed.
Of the 642 ETN-treated patients, 635 (99%) agreed to transition from originator ETN to biosimilar SB4, of whom 625 patients (433 with rheumatoid arthritis, 128 with psoriatic arthritis, and 64 with ankylosing spondylitis) were included in the transition cohort, and 600 ETN-treated patients from 2014 were included in the historical cohort. The crude treatment persistence rate for biosimilar SB4 over 6 months was 90% (95% confidence interval [95% CI] 88-93%), compared to a 6-month treatment persistence rate of 92% (95% CI 90-94%) for originator ETN. Patients in the transition cohort, compared to the historical cohort, had a statistically significantly higher relative risk of treatment discontinuation (adjusted hazard ratio 1.57, 95% CI 1.05-2.36) and showed smaller decreases in the CRP level (adjusted difference 1.8, 95% CI 0.3-3.2) and DAS28-CRP (adjusted difference 0.15, 95% CI 0.05-0.25) over 6 months.
Non-mandatory transitioning from originator ETN to biosimilar SB4 using a specifically designed communication strategy resulted in a slightly lower 6-month treatment persistence rate and smaller decreases in disease activity in the transition cohort compared to the historical cohort, but these differences were not considered clinically relevant.