Bead-extraction and heat-dissociation (BEHD): A novel way to overcome drug and matrix interference in immunogenicity testing

Biological therapeutics are foreign antigens and can potentially induce immune response resulting in the formation of anti-drug antibodies (ADA), which in turn may lead to a wide range of side effects. Neutralizing Ab (NAb) is a subset of ADA that can bind to the pharmacological activity regions of therapeutic to inhibit or complete neutralize its clinical efficacy. A cell-based functional NAb assay is preferred to characterize its neutralization activity. However, cell-based NAb assays are often vulnerable to drug interference, as well as interference from numerous serum factors, including but not limited to growth factors and disease-related cytokines. Bead Extraction with Acid Dissociation (BEAD) has been successfully applied to remove circulating drug and/or other interfering factors from human serum samples, thereby enriching for ADA/NAb. However, the harsh acid used in the extraction procedure can cause irreversible denaturing of NAb and lead to underestimated NAb measurement. Herein we describe a new approach when acid-dissociation is not optimal for a PEGylated domain antibody (Ab). We further demonstrate that heating at 62 °C can not only dissociate drug/ADA/NAb immune complex but also selectively and irreversibly denature domain Ab drug due to much lower thermal stability of the domain Ab, when compared to that of full antibodies. The irreversible denaturing of the drug favors the formation of an immune complex between ADA/NAb and the added biotinylated drug thus increasing the recovery of ADA/NAb from samples. We call this new procedure Bead Extraction with Heat Dissociation (BEHD), which can potentially be applied to other NAb assays that have poor compatibility with acid dissociation.