Regulatory Definitions and Classification of Biosimilar Medications Across the 6 Regions of the World Health Organization

Importance: Biosimilars can improve the accessibility and affordability of biologic medicines, but regulatory harmonization is needed to ensure consistent biosimilar policies and to support comparability with the original biologic reference product (RP). Currently, global regulatory policies and requirements remain inconsistent. Objectives: To summarize and compare regulations and policies regarding biosimilar medications, by World Health Organization (WHO) region. Evidence Review: This scoping review followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses-Extension for Scoping Reviews to search the Cumulative Index to Nursing and Allied Health Literature, PubMed, and Scopus (from inception to March 2026) for regulatory guidance on biosimilar medications in the most populous countries in each WHO region. Emerging and developing and advanced economies, terms defined by the International Monetary Fund, were included. Relevant eligible articles contained at least 1 term for biosimilar medication and 1 or more terms from an additional category across 3 different search protocols. Regulatory parameters (defined by WHO guidelines) were summarized and compared between and among countries. Findings: The regulatory guidelines of 19 countries (12 with emerging and developing and 7 with advanced economies) were included. The term biosimilar was common, with most countries defining biosimilarity as the absence of differences in the medicine's quality, safety, and efficacy compared with the RP. Sixteen countries explicitly required comparability exercises to demonstrate biosimilarity, and 13 countries specified that the same RP must be used in these studies. In 9 emerging and developing and in all 7 advanced economies, regulatory guidance defined use of nonlocally approved comparators and bridging studies if the RP used in comparability studies was not licensed locally. Guidelines related to manufacturing, including assessment of impurities and product stability, were available in most countries, but there were marked differences in requirements for in vivo, in vitro, and clinical studies. All advanced economies waived the need for clinical efficacy and immunogenicity testing when justifiable, but guidelines from emerging and developing economies differed on clinical study waivers. Interchangeability guidance was absent in all emerging and developing economies except Nigeria and Poland. Eleven countries required pharmacovigilance plans for inclusion in biosimilar applications. Conclusions and Relevance: This scoping review provides a detailed comparison of biosimilar regulatory guidelines across all WHO regions and identified similarities and differences that may limit the transferability of data between and among countries. These barriers can potentially affect medication availability, price, access, and reimbursement of biosimilars.