Clinical evidence and implementation guidance for biosimilar switching in ankylosing spondylitis

Biosimilar tumor necrosis factor inhibitors provide therapeutically equivalent alternatives to reference biologics for ankylosing spondylitis (AS) management at reduced costs. Clinical adoption depends on the confidence that switching stable patients from reference products to biosimilars maintains disease control. This review synthesizes the evidence on biosimilar switching in AS populations from regulatory approval programs, randomized controlled trials, and real-world observational studies. It is presented as a structured narrative review based on searches of PubMed, EMBASE, and the Cochrane Library, covering publications from January 2013 to March 2025. Approved biosimilars achieve molecular similarity and therapeutic equivalence to the reference products through analytical characterization, functional equivalence studies, and clinical comparability trials. Randomized switching trials demonstrate maintained efficacy and comparable safety profiles when patients with stable AS transition from the reference infliximab to biosimilar formulations. Immunogenicity profiles demonstrate equivalence between products. Multinational registry data corroborate these findings across diverse healthcare systems. Retention rates and disease activity outcomes are comparable between biosimilars and reference products when baseline patient characteristics are considered. Successful implementation requires patient engagement through transparent communication about biosimilar development and switching evidence. Individualized monitoring protocols should be tailored to baseline disease stability. Clinicians should recognize nocebo effects as a distinct contributor to switching outcomes and apply structured management strategies to address them. The accumulated evidence supports biosimilar switching as an appropriate clinical therapeutic strategy for AS patients with stable responses on reference biologics. This approach offers healthcare cost reductions without compromising treatment outcomes.