Understanding Immunogenicity Testing
Immunogenicity refers to the ability of a therapeutic substance to elicit an immune response in treated individuals. Understanding when and how this response occurs is fundamental for evaluating drug performance, ensuring patient safety, and designing appropriate development strategies.
what is immunogenicity?
Immunogenicity testing assesses the measurement of antibodies generated against a therapeutic drug and supports the interpretation of its safety and efficacy. Immunogenicity is mandatory for therapeutic proteins in clinical studies, a core element of case‑by‑case risk evaluations, and an important component of studies involving peptides, oligonucleotides, and similar modalities.
The tiered immunogenicity workflow
Immunogenicity assessment relies on a structured, multi‑tier workflow designed to support sensitive ADA detection, confirm specificity, and characterize the magnitude and functional impact of immune responses. This approach is widely used across preclinical and clinical programs and is consistent with current regulatory expectations.
Screening assay — initial detection of binding antibodies
The screening assay is designed to detect any antibodies capable of binding to the therapeutic protein. It is commonly run using a ligand‑binding format, such as a bridging ELISA or electrochemiluminescent assay, where the drug is used for both capture and detection. A statistical cut‑point is applied to distinguish negative from presumptively positive samples, and the assay is developed to be sensitive and tolerant to the presence of residual drug to reduce the risk of false‑negative results.
Confirmatory assay — verifying specificity
Samples that screen positive are further evaluated in a confirmatory assay to determine whether the observed signal reflects specific binding to the therapeutic protein. This is typically achieved by adding an excess of unlabeled drug to compete for antibody binding. A reduction in signal indicates that the antibodies are drug‑specific, allowing true ADA‑positive samples to be distinguished from non‑specific interactions.
Titer determination — estimating the magnitude of the ADA response
For samples confirmed as positive, titer determination is used to estimate the relative magnitude of the ADA response. Serial dilutions of the sample are tested to identify the highest dilution that still produces a signal above the assay cut‑point. This information helps characterize how robust the immune response is and how it may evolve over time.
Neutralizing antibody assessment — evaluating functional impact
Neutralizing antibody (NAb) assays assess whether ADA interfere with the therapeutic protein’s biological activity, typically by blocking its interaction with the intended target. Depending on the drug’s mechanism of action, this may involve a cell‑based functional assay or a competitive ligand‑binding format. Identifying neutralizing activity is important because these antibodies may affect clinical efficacy or safety.
how the tiers work together
The tiered workflow forms a cohesive analytical framework that supports sensitive and regulatorily aligned immunogenicity assessment across development phases.
Together, the tiers enable:
- Screening identifies potential responders
- Confirmation ensures specificity
- Titering characterizes the response magnitude
- NAb evaluation clarifies functional relevance
This structure supports sensitive, reproducible, and regulatorily aligned immunogenicity assessments across all development phases.
References
GUIDANCE DOCUMENT from FDA: Immunogenicity Testing of Therapeutic Protein Products — Developing and Validating Assays for Anti-Drug Antibody Detection, 2019. https://www.fda.gov/media/119788/download
GUIDANCE DOCUMENT from EMA: Guideline on Immunogenicity assessment of therapeutic proteins, 2017. https://www.ema.europa.eu/en/documents/scientific-guideline/guideline-immunogenicity-assessment-therapeutic-proteins-revision-1_en.pdf
