FDA Guidance on Biosimilars Highlights Glycosylation Profiling and Increases the Strategic Value of Patents Covering Antibodies Defined by Glycosylation
FDA’s September 2025 guidance requires detailed characterization of posttranslational modifications (PTMs), particularly glycosylation, when evaluating protein biosimilars. Manufacturing processes affect protein characteristics beyond the primary sequence, including PTMs. These features are critical for clinical function and for determining whether a biosimilar is ‘highly similar’ to a reference product. For antibodies, the glycosylation profile is especially important for function and potency. This regulatory focus enhances the strategic value of patents covering antibodies defined by specific glycosylation profiles.
FDA Recommendations for Characterizing Glycosylation
The FDA guidance underscores the need for sponsors to thoroughly characterize glycosylation profiles, especially for antibodies, when seeking clinical approval and/or demonstrating biosimilarity. Glycosylation profiling should include the nature, location, and levels of glycosylation, the distribution across isoforms, and the range of glycan heterogeneity resulting from expression systems and manufacturing conditions. See page 11 of the guidance. The FDA explicitly recognizes that subtle differences in glycosylation can materially influence potency and clinical performance. Sponsors are expected to understand how manufacturing choices, such as expression host, culture conditions, purification methods, can drive glycosylation or glycation heterogeneity and how those differences may affect safety and efficacy. See, e.g., pages 7-8.
The FDA allows sponsors flexibility in selecting analytical methods for biosimilar submissions, including functional assays and non-validated methods. However, the FDA guidance states that “the methods used to characterize the product should be scientifically sound, fit for their intended use, and provide results that are reproducible and reliable.” See pages 11–12.
FDA Research Reinforces the Regulatory Focus
FDA research into rapid glycan analytics supports this regulatory focus. For example, FDA scientists developed a lectin microarray for rapid and accurate glycan-profiling of intact therapeutic antibodies, revealing meaningful differences between biosimilars and referenced products. This FDA-developed technology enables high-throughput comparative glycan profiling, aligning with the agency’s regulatory expectations. Taken together, this suggests that glycosylation is becoming more central to the evaluation of antibody and biosimilar products for regulatory approval.
Strategic Implications for Patent Protection
The FDA recommends demonstrating high glycan similarity with the reference product to meet biosimilar standards. This regulatory emphasis on detailed glycosylation patterns creates opportunities to extend patent protection for antibodies defined by specific glycosylation profiles. Such patents offer an alternative route to exclusivity, complementing traditional approaches. However, these requirements also present challenges in generating sufficient glycan characterization data, managing costs, and securing effective patent claims.
The foundation for an assessment and a demonstration of biosimilarity between a proposed product and its reference product includes analytical studies that demonstrate that the proposed product is highly similar to the reference product notwithstanding minor differences in clinically
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inactive components. The demonstration that the proposed product is biosimilar to the reference product involves robust characterization of the proposed product, including comparative physicochemical and functional studies with the reference product. The information gained from
these studies is necessary for the development of a proposed product as a biosimilar.
