Drug Removal Strategies in Competitive Ligand Binding Neutralizing Antibody (NAb) Assays: Highly Drug-Tolerant Methods and Interpreting Immunogenicity Data

Neutralizing anti-drug antibody (NAb) assays often have lower drug tolerance (DT) than trough drug concentrations, potentially under-estimating NAb incidence. To improve DT, drug-specific proteins were coupled to magnetic beads to deplete drug in the sample. To avoid interference from carryover, drug-specific proteins that did not interfere in the NAb assay, such as target or non-blocking anti-drug antibodies, were selected. With the drug depletion step, DT improved by > 10-fold in two competitive ligand binding NAb assays. Analysis of anti-drug antibody positive clinical samples with elevated drug levels demonstrated that NAb incidence was under-estimated without the drug depletion step. However, these NAb-positive samples had low titer and no impact on drug concentrations.