Neutralizing Antibody Testing
Neutralizing antibodies (NAbs) can block the biological activity of a therapeutic product and thereby impact drug efficacy, pharmacokinetics (PK), pharmacodynamics (PD), and clinical outcomes. Detecting and understanding NAb formation is an important component of immunogenicity risk assessment when antibody responses have the potential to alter drug function.
Mercodia provides regulatory-aligned NAb assay development and validation as well as sample testing services.
Neutralizing Antibodies
Neutralizing antibodies (NAbs) are antibodies produced by the host immune system that block the biological activity of their target. NAbs represent a functionally relevant subset of anti-drug antibodies (ADAs). These antibodies typically bind epitopes within or near the active or functional domain of the therapeutic drug, preventing interaction with the intended biological target. As a result, NAb formation may lead to reduced or abolished pharmacological activity, altered pharmacokinetics, loss of efficacy, and, in some cases, safety concerns.
Because not all ADAs are neutralizing, NAb assessment is generally performed as a follow-up to ADA detection, when there is a scientific or clinical rationale to evaluate functional impact.
Why NAb testing is important
- Block binding of the therapeutic to its biological target
- Reduce or eliminate pharmacological effect
- Contribute to loss of efficacy
- Impact dosing strategies or long-term treatment response
NAb assessment builds on ADA results and is often required when ADA formation may affect drug function.
NAbs testing strategies
The strategy for assessing neutralizing potential in ADA-positive samples should be based on the mechanism of action (MoA) of the therapeutic product. Broadly, two categories of NAb assays are applied: cell-based assays and non-cell-based (ligand-binding) assays.
Regulatory perspectives on assay formats
Regulatory agencies have historically shown a preference for cell-based NAb assays, because these formats measure inhibition of drug activity in a biologically relevant system. However, cell-based assays are often labor-intensive and highly variable and may present challenges related to serum and drug tolerance.
Non‑cell‑based assays as an alternative
In contrast, non-cell-based assays, such as competitive ligand-binding formats, measure inhibition of drug-target interaction directly. These assays can offer higher sensitivity, wider dynamic range, increased precision, and better matrix tolerance compared with cell-based assays. The selection of an appropriate NAb assay format (cell-based or non-cell-based assay) is driven by the therapeutic mechanism of action (MoA), assay performance characteristics, immunogenicity risk and study phase.
Mercodia’s expertise in NAb strategies
With over 30 years of experience in immunoassay development, Mercodia supports the design and execution of fit-for-purpose NAb strategies, ensuring that neutralizing activity is assessed when scientifically and clinically relevant.
Further reading
For further information about the development and validation of anti-drug antibody detection assays and neutralization assays, you can read: “Immunogenicity testing of therapeutic protein products – developing and validating assays for anti-drug antibody detection. Guidance for Industry”.
Our NAb Testing Capabilities
Ligand‑Binding NAb Assays
- Tailored to therapeutic structure and mechanism of action
- Designed to model drug–target competition
- Well-suited for programs where cell‑based formats are not required
Cell based assay NAb Assays
- Generally recommended by FDA, however, depending on the drug mode of action (MOA), alternative strategies may be appropriate.
Assay Development, Validation & Sample Testing
- Custom NAb assay design aligned with therapeutic MoA
- Fit‑for‑purpose or fully validated methods in accordance with regulatory guidelines
- Clinical sample testing, including analysis of ADA-positive samples to assess neutralizing activity
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Related Resources
References
- 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
- 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.
- 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
