The development of neutralizing antibody (NAb) assays presents unique bioanalytical challenges, primarily driven by the inherent complexity of incorporating the therapeutic mechanism of action (MOA) into the immunogenicity characterization. Unlike conventional anti-drug antibody assays, NAb assay design demands a thorough mechanistic understanding of the biotherapeutic and its pharmacological target, adding a layer of scientific and technical complexity. Assay format selection is a multifactorial process, influenced by critical parameters including the therapeutic MOA, the degree of matrix interference, and the availability and suitability of critical reagents. Navigating these interdependent variables requires a fit-for-purpose approach that balances scientific rigor with practical feasibility that falls within regulatory guidelines. Beyond technical design, strategic decisions surrounding the timing and necessity of NAb assay implementation are equally critical. These decisions must be informed by a thorough immunogenicity risk assessment of the molecule in question, as well as careful consideration of complementary bioanalytical data available within the broader clinical testing paradigm.

The accurate detection of anti-drug antibodies (ADAs) and neutralizing antibodies (NAbs) is fundamental to the comprehensive clinical characterization of biotherapeutic safety and efficacy. As the complexity of biotherapeutic modalities continues to increase, the development of robust immunogenicity assays capable of reliably detecting clinically relevant antibody responses remains a critical priority within the drug development and regulatory landscape. The inherent complexity of ADA and NAb assay platforms introduces significant analytical challenges, particularly with respect to interfering factors such as circulating drug and soluble target interference. When unaddressed, these interfering factors can compromise assay sensitivity and specificity, leading to false positive or false negative results that may obscure the true immunogenic profile of a biotherapeutic and impact downstream clinical decision-making. Effective mitigation of matrix interference is dependent upon multiple factors, as the optimal strategy is highly dependent upon the drug modality and its mechanism of action. A thorough understanding of these interdependencies is essential for designing fit-for-purpose assays that maintain analytical integrity across varying drug concentration ranges and disease states.

The purpose of this short course is to share experience gained in preparing immunogenicity documents for regulatory purposes such as the “Integrated Summary of Immunogenicity (ISI)” to best describe the immunogenicity risk and the steps taken to assess and mitigate it. We will overview examples of the multi-disciplinary information that is most useful for the regulator assessing the scale of risk of undesirable immunogenicity for overall clinical benefit vs. risk for proteins, peptide, oligonucleotide products, both new molecular entities and follow-on. We will also examine the different roles of team members to generate these documents. Lastly, we will provide examples on how to anticipate and address potential issues (and how to avoid introducing any new ones!) by generating a well-thought-out and constructed immunogenicity summary early in development and build on it to develop the ISI.