Analytical Similarity as the Foundation of Biosimilar Development

Biosimilars are increasingly shaping global healthcare systems by providing highly similar alternatives to approved biologic medicines with no clinically meaningful differences in safety, purity or potency. Unlike generic small-molecule drugs, biosimilars are complex biological products produced in living systems, requiring extensive analytical characterization and regulatory evaluation to demonstrate similarity to a reference product.

Since the European Medicines Agency (EMA) approved the first biosimilar in 2006 and the US Food and Drug Administration (FDA) followed in 2015, regulatory frameworks and scientific expectations have continued to mature. As development activity accelerates, biosimilar manufacturers are placing greater emphasis on analytical rigor, functional comparability and lifecycle compliance to support successful approvals.

Biosimilar market growth and adoption

Biosimilar approvals have increased steadily across major regulatory regions, reflecting growing confidence among regulators, healthcare providers and patients. Trastuzumab provides a clear example of this transition. Originally approved in 1998 for the treatment of certain breast cancers, the first biosimilar version entered the market in 2017, followed by multiple additional approvals worldwide.

Regulatory activity in the biosimilars landscape has accelerated in recent years. 18 biosimilars were authorized in the US and 16 in the EU in 2024. To date, the US has approved more than 60 biosimilars across 15 reference molecules, while the EU has exceeded 100 approvals spanning 19 reference molecules.

This momentum continued in 2025, when the FDA approved the first monoclonal antibody biosimilar, Ustekinumab, without requiring a traditional Phase III clinical efficacy trial. This milestone represents a pivotal shift toward more streamlined, evidence-based regulatory pathways, underscoring increasing reliance on advanced analytical characterization and pharmacokinetic/pharmacodynamic (PK/PD) comparability data to support biosimilar approval.

Market projections indicate sustained growth over the coming decade, supported by patent expirations, increasing prevalence of chronic diseases and advances in biomanufacturing technologies. 

Analytical similarity as the foundation of biosimilar development

Demonstrating analytical similarity remains the cornerstone of biosimilar development. Because biologics exhibit inherent variability, developers must establish similarity through comprehensive analytical characterization rather than by demonstrating identical composition.

Development begins with a comparative evaluation of the biosimilar and reference product to define the quality target product profile (QTPP), which guides subsequent process development and analytical strategy.

Key elements of physicochemical characterization include:

• Primary structure
  
  Primary structure analysis confirms amino acid sequence integrity and identifies post-translational modifications or sequence variants. Techniques commonly include intact mass analysis, peptide mapping, terminal sequencing and disulfide bridge analysis

• Higher order structure
  
  Secondary and tertiary structures define the three-dimensional conformation critical to biological function. Analytical methods such as circular dichroism, Fourier transform infrared spectroscopy and fluorescence-based techniques are applied to evaluate structural comparability

• Product variants and impurities
  
  Assessment of glycoforms, charge variants and aggregates is essential because these attributes can influence stability, efficacy and immunogenicity. Chromatographic, electrophoretic and light-scattering approaches are typically combined to provide a comprehensive assessment

Functional characterization and mechanism of action

While structural analysis establishes molecular similarity, functional characterization confirms that comparable structures translate into equivalent biological activity.

Functional assays evaluate the mechanism of action and contribute to the regulatory 'totality of evidence' framework used by global authorities.

Common approaches include:

• Binding assays measuring affinity and kinetics using ELISA, surface plasmon resonance, bio-layer interferometry and flow cytometry
• Cell signaling assays assessing activation or inhibition of disease-relevant pathways
• Effector function assays evaluating immune-mediated mechanisms such as antibody-dependent cell-mediated cytotoxicity and complement activation
• Cell-based potency assays measuring proliferation, viability or cytotoxic responses

Because biological activity is closely linked to structural attributes such as glycosylation patterns or protein modifications, multiple orthogonal assays are typically used to interpret complex mechanisms of action and establish acceptance criteria.

Why SGS?

As biosimilars continue to expand across global healthcare systems, robust analytical and functional characterization remains essential to demonstrate similarity, ensure regulatory compliance and support confidence among patients and clinicians.

We support biosimilar developers throughout this process with integrated analytical, functional and regulatory expertise. Through our global network of GMP-compliant laboratories and advanced analytical technologies, we help manufacturers establish analytical similarity, validate methods and generate the data required for successful regulatory submissions and lifecycle management.

Watch our webinar to gain deeper insights from our experts and learn how these strategies support successful biosimilar development during their presentation and live Q&A.