Uptake of tumour necrosis factor-alpha inhibitor biosimilars for psoriasis: a drug utilization study from the British Association of Dermatologists Biologic and Immunomodulators Register (BADBIR)

Background Tumour necrosis factor-alpha inhibitors (TNFi) have revolutionized the treatment of moderate-to-severe psoriasis. Following patent expiry of the originator biologics, TNFi biosimilars became available, presenting the opportunity for significant reductions in drug costs. Objectives To describe the uptake of TNFi biosimilars for psoriasis treatment in the UK and Ireland. Methods This observational cohort study utilizes data from the British Association of Dermatologists Biologic and Immunomodulators Register (BADBIR), a national pharmacovigilance study register for patients with psoriasis on systemic treatments. We analysed biosimilar uptake trends over time in nine geographical regions of England along with Wales, Scotland, Northern Ireland and the Republic of Ireland. We assessed the incidence of switching to biosimilars in an originator-user cohort (switchers). Patients on originators infliximab, etanercept and adalimumab at the time originator patents expired, entered the cohort on 1 February 2015, August 2015 and October 2018, respectively, and were followed up until 31 October 2021. Trends in biosimilar initiations were assessed in an adalimumab-naive cohort who started adalimumab between 1 October 2018 and 31 July 2019 (starters). We assessed the associations between patient factors and originator-to-biosimilar switching and biosimilar initiation using a multivariable Cox regression model and a multivariable logistic regression model, respectively. Results Included in the originator-user cohort were 4202 patients (209 on infliximab, 742 on etanercept and 3251 on adalimumab). For infliximab, etanercept and adalimumab, respectively, the cumulative incidence of originator-to-biosimilar switching increased with time to 14.8%, 23.6% and 66.6% after 3 years. Across geographical regions, 3-year switching rates varied from 0% to 43.7% for infliximab; from 0% to 40.4% for etanercept; and from 12.5% to 84.3% for adalimumab. Out of the 528 patients included in the adalimumab-naive cohort, 67.8% started on biosimilars. Originator-to-biosimilar switching and biosimilar initiation were more common in men and in patients who had lower Psoriasis Area and Severity Index at cohort entry. Conclusions The uptake of biosimilars increased over time and varied considerably across the UK and Ireland; adalimumab had the highest biosimilar uptake rate compared with that of other TNFi drugs. Tumour necrosis factor-alpha inhibitors (TNFi) are widely prescribed for patients with moderate-to-severe psoriasis. Following patent expiry of TNFi originators, TNFi biosimilars became available, presenting the opportunity for significant reductions in drug costs. We conducted a study looking at the uptake of biosimilars using data from the British Association of Dermatologists Biologic and Immunomodulators Register (BADBIR), a large multicentre register of patients with severe psoriasis based in the UK and Ireland, and showed that the rate of switching to or starting TNFi biosimilars increased over time and varied across regions. Biosimilar use was found to be more common in men or patients with low disease severity.