Drug survival and safety of biosimilars and originator adalimumab in the treatment of psoriasis: a multinational cohort study

INTRODUCTION: Psoriasis is a chronic inflammatory skin disease. Adalimumab is an effective but previously expensive biological treatment for psoriasis. The introduction of biosimilars following the patent expiry of the originator adalimumab Humira has reduced the unit cost of treatment. However, the long-term effectiveness and safety of adalimumab biosimilars for treating psoriasis in real-world settings are uncertain and may be a barrier to widespread usage. METHODS AND ANALYSIS: This study aims to compare the drug survival and safety of adalimumab biosimilars to adalimumab originator for the treatment of psoriasis. We will use both routinely collected healthcare databases and dedicated pharmacovigilance registries from the PsoNet initiative, including data from the UK, France and Spain. We will conduct a cohort study using a prevalent new user design. We will match patients on previous adalimumab exposure time to create two equal-sized cohorts of biosimilar and originator users. The coprimary outcomes are drug survival, defined by the time from cohort entry to discontinuation of the drug of interest; and risk of serious adverse events, defined by adverse events leading to hospitalisation or death. Cox proportional hazards models will be fitted to calculate HRs as the effect estimate for the outcomes. ETHICS AND DISSEMINATION: The participating registries agree with the Declaration of Helsinki and received approval from local ethics committees. The results of the study will be published in scientific journals and presented at international dermatology conferences by the end of 2023.