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

Duc Binh Phan, Anthony P Bewley, Catherine H Smith, Teena Mackenzie, Christopher E M Griffiths, Mark Lunt, Richard B Warren, Zenas Z N Yiu

Research output: Contribution to journalArticlepeer-review

Abstract

BACKGROUND: Tumour necrosis factor-alpha inhibitors (TNFi) have revolutionised the treatment of moderate to severe psoriasis. Following patent expiration of originators, 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 United Kingdom (UK) and the Republic of Ireland (RoI).

METHODS: This observational cohort study utilises data from the British Association of Dermatologists Biologics and Immunomodulators Register (BADBIR), a national pharmacovigilance register for psoriasis patients on systemic treatments. We analysed biosimilar uptake trends over time in 9 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 1st February 2015, August 2015, and October 2018, respectively, and were followed up until 31st October 2021. Trends in biosimilar initiations were assessed in an adalimumab-naïve cohort who started adalimumab between 1st October 2018 and 31st 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: 4202 patients (209 on infliximab, 742 on etanercept, and 3251 on adalimumab) were included in the originator-user cohort. 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. 528 patients were included in the adalimumab-naïve cohort, of whom 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: In conclusion, the uptake of biosimilars increased over time and varied considerably across the UK and RoI; adalimumab had the highest biosimilar uptake rate compared to other TNFi drugs.

Original languageEnglish
JournalThe British journal of dermatology
Early online date5 Apr 2023
DOIs
Publication statusE-pub ahead of print - 5 Apr 2023

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