The Tailored Biosimilar Approach: Expectations and Requirements

Regulatory approval of biosimilar medicines currently requires a combination of physicochemical and functional testing, pharmacokinetic data, and clinical efficacy studies (CES). In this article, we discuss the tailored biosimilar approach, which represents an evolution in regulatory thinking by moving away from the default requirement for CES in biosimilar approval. We explore how physicochemical and functional data can be predictive for clinical performance and address the limitations of CES for regulatory decision-making. We argue that, in most cases, the combination of a robust package of physicochemical and functional testing, with appropriately designed pharmacokinetic studies provides sufficient evidence to establish biosimilarity. Additionally, we provide our perspective on the requirements, expectations, and exceptions for future biosimilar approvals, outlining specific scenarios where additional clinical evidence may be necessary. These include cases where the mechanism of action is unknown or poorly characterized, when product heterogeneity cannot be adequately characterized, or where relevant safety or immunogenicity concerns arise with the reference product or biosimilar candidate. Finally, we aim to clarify the remaining concerns surrounding the tailored biosimilar approach, providing insights into the potential to streamline biosimilar development and regulatory approval.