Neutralizing antibodies (NAbs) are a subset of Anti-drug antibodies (ADAs) that play an important role in understanding the efficacy and safety of a drug product. While most drugs are associated with low risk and do not require a validated NAb assay prior to testing Phase 3 samples, drugs associated with high-risk Nabs require testing much earlier (early Phase I). NAb assays are typically performed on samples that confirm positive for ADAs. The results from a NAb assay are semi-qualitative and gives a positive (indicates neutralizing potential) or negative (none neutralizing). Positive samples can be further analyzed by titering which correlates the number of adverse events. Neutralizing antibodies can directly inhibit drug function and potentially inhibit the binding of the drug product to its target.

When deciding between a cell-based NAb assay and a non-cell-based competitive ligand binding assay, the drug’s mode of action must first be understood. Cell-based NAb assays should be considered when the target is a cellular receptor in which the drug binds and activates. Meanwhile, a non-cell-based assay is preferred when the drug has a humoral target, allowing the drug to bind and inhibit the target. In some cases, a highly sensitive PD marker and/or a well-designed PK assay can be used in lieu of an NAb assay. An in-depth understanding of the drug and the mode of action is essential in determining the best NAb assay format and the type of assay output required.

In the 2019 FDA Immunogenicity guidance it states that cell-based NAb assays should be used whenever possible, due to the ability to mimic NAb mechanism of action invivo. While this remains the focus, cell-based assays can be difficult to develop due to matrix effects, reproducibility, and drug interference. It is also important to determine the most appropriate functional outcome of the cell-based NAb assay including cell proliferation signal transduction, specific enzyme activity, cytotoxicity, or reporter gene activity. Cell-based NAb assays are not only an expensive endeavor and require significant time to develop. Identifying a commercially available positive control or generating a positive control with neutralizing capabilities is a key aspect of both cell and ligand-binding NAb assays. At KCAS Bio, we have both the knowledge and experience as well as dedicated lab space to assist you with your NAb development and validation. 

KCAS Bio has dedicated lab space to meet all your NAb development and sample analysis needs.  We have an experienced team of scientists with both cell-based and non-cell-based NAb experience and can assist you. We have in-depth knowledge when it comes to troubleshooting and overcoming challenges such as drug interference and matrix variability. We look forward to working with you on your next NAb study.