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Neutralizing Antibody Assays

Neutralizing antibodies are antibodies that originate in the organism and their function is to protect cells from external agents such as viruses, bacteria, and microbial toxins.


Neutralizing Antibody Assay

Neutralizing antibodies (NAbs) are antibodies that originate in the organism and their function is to protect cells from external agents such as viruses, bacteria, and microbial toxins.

NAbs are a subset of anti-drug antibodies (ADA)  from therapeutic protein treatment. These antibodies bind epitopes within or near the active site of the therapeutic drug. This action prevents the drug from interacting with its target and results in compromised pharmacokinetics, efficacy, and safety of the treatment (1).

The method for the assessment and measurement of neutralizing potential for ADA-positive samples should be based on the mechanism of action of the therapeutic protein product (2). It is possible to identify two different methods of quantification: cell-based and non-cell-based.

As it has been pointed out by several researchers, international regulatory agencies prefer cell-based assays because they rely on cellular responses to NAb-mediated inhibition of therapeutic antibodies. Based on their detection methods, these assays are considered more biologically relevant than non-cell-based assays (3). It is however important to emphasize that cell-based assays are labor intensive, highly variable, presenting low serum tolerance and poor drug tolerance. Opposite to cell-based assays, non-cell-based assays often rely on the binding of the drug and target for signal detection and quantitation (3).

Among different detection techniques, competitive ligand binding assays can be used to characterize NAbs, providing higher sensitivity, wider dynamic range, increased precision, and better matrix tolerance than cell-based assays (3). The selection of the quantification method (cell-based or non-cell-based assay) is driven by different criteria that might include the therapeutic mechanism of action, assay performance characteristics, and risk of immunogenicity (3).

Mercodia with its 30 years’ experience in the development of immunoassays, offers bioanalytical testing services for drug development, keeping in mind the requirements for the detection of NAbs when required.

For further information about the development and validation of anti-drug antibody detection assays and neutralization assays, you can read through: “Immunogenicity testing of therapeutic protein products – developing and validating assays for anti-drug antibody detection. Guidance for Industry” (2).


  1. Peek VL, Lemen DM, Konrad RJ, Wen Y. A competitive ligand binding assay for detection of neutralizing antibodies against an insulin analog [published online ahead of print, 2023 Oct 14]. J Immunol Methods. 2023;523:113575. doi:10.1016/j.jim.2023.113575
  2. Immunogenicity Testing of Therapeutic Protein Products —Developing and Validating Assays for Anti-Drug Antibody Detection. 2019. https://www.fda.gov/regulatory-information/search-fda-guidance-documents/immunogenicity-testing-therapeutic-protein-products-developing-and-validating-assays-anti-drug.
  3. A competitive ligand-binding assay for the detection of neutralizing antibodies against dostarlimab (TSR-042). AAPS Open 7, 8 (2021). https://doi.org/10.1186/s41120-021-00039-w

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Andreas Almlén

Key Account Manager Distributors and OEM

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