Real-World Evidence for Biosimilar Interchangeability Across Therapeutic Areas

Biosimilar switching has moved from an isolated clinical question to a recurring feature of biologic treatment. The evidence base now includes randomized switching trials, prospective and retrospective real-world cohorts, systematic reviews, and experience with multiple and biosimilar-to-biosimilar switches. However, “interchangeability” is not a uniform clinical or regulatory construct, and apparently concordant findings can conceal substantial differences in product, disease, switching sequence, immunogenicity assessment, persistence, and implementation context. To evaluate how real-world evidence contributes to judgments about biosimilar interchangeability across therapeutic areas and to identify where evidence can be transferred, where it must remain product- or context-specific, and where uncertainty persists. An umbrella-review framework was used to integrate systematic-review evidence with selected methodological, randomized, analytical, and real-world studies required to interpret switching effectiveness, safety, immunogenicity, persistence, multiple switching, and therapeutic-area variation. Review quality, primary-study overlap, differences in endpoint definitions, and the distinction between analytical, pharmacological, clinical, and implementation evidence were treated as separate dimensions of interpretation. Across therapeutic areas, the assembled evidence is broadly reassuring for appropriately evaluated switches between reference biologics and biosimilars. Controlled studies provide particularly strong support for specified switching schedules, whereas real-world studies add information on persistence, treatment discontinuation, patient experience, mandatory switching, and repeated transitions. Confidence decreases when evidence is transferred between products, switching sequences, indications, assay systems, or health-system contexts that were not directly studied. Real-world evidence strengthens the clinical evidence base for biosimilar switching but does not make interchangeability a context-free property. A defensible interpretation requires convergence across product similarity, clinical effectiveness, safety, immunogenicity, switching sequence, and therapeutic setting while retaining explicit uncertainty when these layers do not align.