Bioanalytical Scheme for Antidrug Neutralizing Antibody Assays

In standard tiered immunogenicity testing, antidrug antibodies positive clinical samples should be further characterized for their neutralizing capacity through in vitro neutralizing antibody (NAb) assays. In this chapter, the authors first discuss the strategy for NAb assay format selection and when a NAb assay is needed, followed by important considerations and challenges associated with NAb assay development, validation, and method transfer. Cell-based NAb assays use cells to detect NAb activity that inhibits the drug-mediated cellular response. This assay format was traditionally preferred by regulatory agencies. Risk of immunogenicity is the primary guide for the NAb testing bioanalytical strategy. The impact of immunogenicity, although often none or benign, could potentially impact drug efficacy and patient safety. Once an assay has been developed, it usually needs to be validated prior to sample testing. The parameters for a NAb assay validation generally include cutpoint, accuracy and precision, sensitivity, selectivity, and specificity.