Abstract
Adalimumab is a monoclonal antibody approved for managing inflammatory bowel disease (IBD) and other autoimmune conditions. Biosimilars can offer a more affordable alternative to reference biologics and improve access to treatments. Despite their advantages, there are still concerns regarding physicians' adoption of biosimilar products. This study aimed to compare the clearance of originator adalimumab with its biosimilar products in patients with inflammatory bowel disease and other autoimmune diseases. This multicenter retrospective study was conducted across seven hospitals in Saudi Arabia and Qatar. The study population included adult patients who received adalimumab and underwent routine therapeutic drug monitoring. Population pharmacokinetic analysis was performed using Monolix software, and the empirical Bayesian estimate of clearance was determined for individual patients. Stepwise linear regression was then conducted to assess the effects of product type and other covariates on adalimumab clearance. This study included a total of 99 patients. Patients received various adalimumab products, including the reference biologic (Humira, 70.7%) and biosimilars (Amgevita, 16.2%; Hyrimoz, 13.1%). The average estimated clearance was 0.018 ± 0.012 L/hr. The only significant covariates in the multivariable regression were age and the presence/absence of antibodies. There was no significant difference in clearance between the originator and biosimilar products. Our study compared the clearance of adalimumab originator and its biosimilars in patients with inflammatory bowel disease and other autoimmune disorders. No significant differences in clearance were observed, suggesting comparable clearance. The adoption of biosimilars in clinical practice could improve patient access to biologic therapies while substantially reducing healthcare costs.