ADA assays for high-dose biologics: redefining drug tolerance through clinical insights

The validation of anti-drug antibody (ADA) assays is vital in biologics development, with regulatory bodies like EMA and FDA emphasizing drug tolerance. In patient care, drug tolerance assessments should reflect actual clinical use. We developed an ADA assay for a fully human monoclonal antibody used in oncology, addressing the challenges posed by high circulating drug levels and target biology. Various assay formats were tested using multiple positive controls and drug concentrations that mimic real-world exposure and drug-to-ADA ratios. Assessing different positive controls at various concentrations was key to characterizing sensitivity and drug tolerance. An assay initially showing low drug tolerance with one monoclonal control performed adequately with others. Rather than limiting assessments to a single sensitivity level, we evaluated assay performance using clinically relevant drug and ADA concentrations. This approach ensures the assay's sensitivity and drug tolerance are meaningful for patient management and therapeutic decisions. Early and ongoing collaboration with health authorities supported alignment of clinically relevant performance criteria and interpretation strategies. Ultimately, this patient-oriented strategy guarantees ADA results that inform patient safety and treatment effectiveness for high-dose biologic therapies.