P66 Uptake of biosimilars for psoriasis: a drug utilization study from the British Association of Dermatologists Biologics and Immunomodulators Register
Authors: Phan Duc Binh , Bewley Anthony , Smith Catherine , Mackenzie Teena , Griffiths Christopher , Lunt Mark , Warren Richard , Yiu Zenas 
Published: June 2023

Abstract
Tumour necrosis factor-α inhibitors (TNFi) have revolutionized the treatment of moderate-to-severe psoriasis. Following patent expirations of TNFi originators, TNFi biosimilars became available, presenting the opportunity for significant reductions in drug costs. This observational cohort study aimed to describe the uptake of TNFi biosimilars for psoriasis treatment in the UK and Republic of Ireland (RoI). This study utilized data from the British Association of Dermatologists Biologics and Immunomodulators Register (BADBIR), a national pharmacovigilance 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 RoI. We assessed the incidence of switching to biosimilars in an originator-user cohort (switchers). Patients on originator 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-naïve 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. In total, 4202 patients (209 on infliximab, 742 on etanercept and 3251 on adalimumab) were included in the originator-user cohort. For infliximab, etanercept and adalimumab, the cumulative incidence of originator-to-biosimilar switching increased with time to 14.8%, 23.6% and 66.6% after 3 years, respectively. Across geographical regions, 3-year switching rates varied from 0% (North East England, London, Scotland, Northern Ireland, RoI) to 43.7% (East Midlands) for infliximab; from 0% (RoI) to 40.4% (South West England) for etanercept; and from 12.5% (London) to 84.3% (North East England) for adalimumab. After switching to biosimilars, 2.8% of switchers cross-switched to other biosimilars, 1.1% switched back to the originator and 17.1% discontinued or switched to other biologic medicines. In total, 528 patients were included in the adalimumab-naïve cohort, of whom 67.8% started on biosimilars. Amgevita® and Imraldi® were the most commonly used biosimilars among adalimumab biosimilar switchers (56.8% and 39.1%, respectively) and starters (53.6% and 34.4%, respectively). Originator-to-biosimilar switching and biosimilar initiation were more common in patients who were male or had lower a Psoriasis Area and Severity Index at cohort entry. The uptake of biosimilars increased over time and varied considerably across the UK and RoI; adalimumab had the highest biosimilar uptake rate compared with other TNFi.