Real-World Outcomes of a Non-Medical Switch to Adalimumab-Atto Biosimilar: Safety, Effectiveness, and Treatment Persistence in an Adult Saudi Tertiary Care Population.

Background: Adalimumab-atto, a biosimilar to adalimumab, has been widely adopted for managing autoimmune conditions due to its demonstrated safety, efficacy, and cost-effectiveness in clinical trials. However, real-world data from Saudi Arabian population remains limited. Objective: This study aimed to evaluate the persistence, safety, and clinical outcomes of patients transitioned from originator adalimumab (Humira Methods: A retrospective self-controlled cohort study was conducted, including all patients transitioned to adalimumab-atto between January 1 and December 31, 2022, for non-medical reasons. The primary endpoint was treatment persistence at 12 months. Secondary endpoints included disease stability, adverse events, and reasons for discontinuation. Results: The study included 265 adult patients previously treated with originator adalimumab. The mean age of the cohort was 41 ± 13 years, with 46.8% being female. The most common indications were Crohn's disease (40.4%), rheumatoid arthritis (16.6%), and plaque psoriasis (12.1%), with a mean disease duration of 11.7 ± 6.7 years. At 12 months, 90.2% of patients persisted with adalimumab-atto, of whom 79.5% remained stable, while 20.5% were classified as unstable Twenty-six patients (9.8%) discontinued therapy, primarily due to insufficient efficacy (13 patients), with one discontinuation attributed to adverse events. Conclusion: Adalimumab-atto demonstrated high treatment persistence and favorable safety outcomes in a diverse population of patients with autoimmune diseases. These findings support the feasibility of continued use of the biosimilar in patients with immune-mediated diseases.