Incidence of and Reasons and Determinants Associated with Retransitioning from Biosimilar Etanercept to Originator Etanercept

Background: Patients in clinical practice are transitioned from originator etanercept (OR-ETA) to biosimilar etanercept (BS-ETA), but some subsequently retransition. Insights into the incidence of and reasons for retransitioning and the characteristics of these patients could help clinicians successfully introduce biosimilars. Objective: Our objective was to assess the incidence of and reasons for retransitioning from BS-ETA to OR-ETA in patients with a rheumatic disease (RD) and to explore the determinants thereof. Methods: This cohort study included all patients with RD who had transitioned from OR-ETA to BS-ETA in a large hospital in the Netherlands in 2016. The incidence of retransitioning to OR-ETA and the 1-year persistence with BS-ETA were assessed using the Kaplan–Meier estimator. Reasons for retransitioning were classified as related to (1) efficacy, (2) adverse events, (3) the administration device, and (4) other. Determinants for retransitioning, including baseline and treatment characteristics, were assessed in a nested case–control study using conditional logistic regression. Results: We included 342 patients (median age 57.8 years; 53.5% females). At 1 year after transitioning, 9.4% of patients had retransitioned to OR-ETA and 69.7% were persistent with BS-ETA. At the end of follow-up (median 4.4 years), 47 patients (13.7%) had retransitioned to OR-ETA. The median time until retransitioning was 0.55 years (interquartile range 0.2–1.3). Most patients (n = 34 [72.3%]) retransitioned because of a (perceived) loss of effect, followed by adverse events (23.4%). In total 3.8% of patients switched to another biological treatment or a Janus kinase inhibitor; 17.1% of patients discontinued BS-ETA without retransitioning or switching within the first year. Univariate determinants for retransitioning included initiating corticosteroids or intensifying immunomodulator treatment (odds ratio [OR] 2.37; 95% confidence interval [CI] 1.03–5.45) and the number of visits to the rheumatology department (OR 2.06; 95% CI 1.55–2.74). In the multivariate analysis, only the number of visits to the rheumatology department remained significantly associated with retransitioning (OR 2.19; 95% CI 1.60–3.01). Conclusion: When introducing a biosimilar in clinical care, clinicians should anticipate that one in seven patients will retransition to the originator. A (perceived) loss of effect was the most frequently reported reason for retransitioning. Patients who visited the rheumatology department more frequently had an increased risk of retransitioning, which is likely to be related to patients reporting a loss of effect and to adverse events resulting in more visits to the rheumatology department.