Cell-Based vs. Non-Cell-Based NAb Assays: Which Method is Right for Your Research?

Your research on neutralizing antibodies (NAbs) is of utmost importance, as these antibodies can inhibit or block the biological/pharmacological activity of the drug in vivo, potentially impacting its efficacy. This potential impact underscores the urgency and importance of your work. Of most significant concern are antibodies that neutralize the administered drug and neutralize an essential non-redundant endogenous homolog, thereby impairing the body’s normal function². Choosing the correct type of assay—a cell-based or competitive ligand binding (CLB) assay—depends on various factors, including the drug’s mechanism of action and your specific research goals¹.

In cell-based assays, NAbs are detected by their ability to interrupt the signaling events induced or impacted by the drug.  Various endpoints are available for cell-based NAb assays, and their selection relies upon the signaling mechanism utilized or disrupted by the drug product. In contrast, non-cell-based NAb assays are based on the ability of NAbs to interrupt the binding between the drug and its target, either of which may be immobilized on a surface¹.

The choice between non-cell-based and cell-based NAb assays for routine immunogenicity testing is a topic of frequent debate in industry forums. This is especially true if the drug under consideration is a monoclonal antibody therapeutic and the risk of NAbs is limited to loss of efficacy^2,3.

Understanding Cell-Based NAb Assays

• Cell-based assays are more complex and require extended development, optimization, and validation. Cell-based neutralizing antibody (NAb) assays, which utilize live cells to assess the neutralizing activity of antibodies against a specific drug, offer a more physiologically relevant evaluation of the drug’s ability to neutralize the therapeutic. These assays replicate the in vivo environment, providing a robust and reliable method for your research¹

• Regulatory Guidance:

Figure 1. Different methods of comparison between Cell-based Assays and non-Cell-Based Assays

Critical Differences Between Cell-Based and Non-Cell-Based Assays Mechanism of Action:

• Cell-Based Assays: In a cell-based assay, NAbs are detected by their ability to interrupt the signaling events induced or impacted by the drug¹. Various endpoints are available for cell-based NAb assays, and their selection relies upon the signaling mechanism utilized or disrupted by the drug product ^1,2,3.
• Non-Cell-Based Assays: When a cell-based assay becomes a challenge, a viable alternative, non-cell-based assays, may be considered. This could be due to various issues, such as the unavailability of a suitable cell line or assay-related problems like serum toxicity, impaired assay precision, robustness, and sensitivity. The ease of performing non-cell-based assays is appealing; however, whether these assays provide a scientifically relevant system for detecting clinically relevant NAbs compared to a cell-based assay ^2,3,4.
• Complexity and Development:
• Cell-Based Assays: Developing cell-based assays can be challenging due to factors like matrix effects, reproducibility issues, and drug interference. They also require significant time and resources².
• Non-Cell-Based Assays: These are generally easier to develop and validate, making them a more straightforward option for certain applications⁵.
• Regulatory Guidance:
• Regulatory agencies like the FDA and EMA recommend using cell-based assays whenever possible, as they provide a more accurate representation of the drug’s neutralizing activity in vivo
• The FDA suggests using polyclonal positive control antibodies when developing immunological assays like ADA and NAb assays⁵.

Figure 2. The FDA’s view on alternative approaches for NAb testing

Choosing The Right Method for Your Research

When deciding between cell-based and non-cell-based NAb assays, consider the following factors:

• Drug’s Target: A cell-based assay is likely better if your drug targets a cellular receptor. However, a non-cell-based assay could be sufficient for therapeutics targeting soluble molecules².
• Assay Sensitivity: Cell-based assays can offer higher sensitivity and specificity, which is crucial for detecting low levels of neutralizing antibodies^1,2.
• Resource Availability: Cell-based assays require more specialized equipment and expertise². Consider the resources and scientific expertise available in your lab.

Conclusion

Both cell-based and non-cell-based NAb assays have their advantages and limitations. The specific requirements of your research should guide the choice between them, like the therapeutic mechanism of action and the available resources. By carefully considering these factors, you can select the most appropriate assay to ensure accurate and reliable results in your NAb studies. In some studies, the improved ability of the cell-based assay to tolerate drugs could be the primary reason for the significantly higher NAb positive detection rate compared to the CLB assays^1,2.

1. Journal of Immunological Methods – Comparison of cell-based and non-cell-based assay platforms for the detection of clinically relevant anti-drug neutralizing antibodies for immunogenicity assessment of therapeutic proteins https://doi.org/10.1016/j.jim.2015.02.006
2. Journal of Immunological Methods – Recommendations for the design and optimization of immunoassays used in the detection of host antibodies against biotechnology products https://pubmed.ncbi.nlm.nih.gov/17307199/
3. Journal of Immunological Methods – Development and validation of a cell-based bioassay for the detection of neutralizing antibodies against recombinant human erythropoietin in clinical studies https://doi.org/10.1016/j.jim.2004.07.007
4. Journal of Immunological Methods – A risk-based bioanalytical strategy for the assessment of antibody immune responses against biological drugs – https://www.nature.com/articles/nbt1303
5. FDA Guidance – Immunogenicity Testing of Therapeutic Protein Products – Developing and Validation Assays for Anti-Drug Antibody Detection – https://www.fda.gov/regulatory-information/search-fda-guidance-documents/immunogenicity-testing-therapeutic-protein-products-developing-and-validating-assays-anti-drug