Immunogenicity of Antibody–drug Conjugates: Observations Across 8 Molecules in 11 Clinical Trials

<b>Aim:</b> To evaluate the clinical immunogenicity of eight antibody-drug conjugates (ADCs), multi-domain biotherapeutics that could theoretically pose a greater immunogenicity risk than monoclonal antibodies (mAbs) because they contain non-natural structural motifs. <b>Methodology & results:</b> Immunogenicity strategies and assays for these ADCs included those commonly used for conventional biotherapeutics with additional characterization. A tiered approach was adopted for testing Phase I and II clinical study samples with screening, confirmatory assays and additional domain characterization. Antidrug antibody incidences with these ADCs were within those reported for mAb biotherapeutics with no apparent impact on clinical outcomes. <b>Conclusion:</b> These data suggest that the ADC hapten-like structure across these eight ADCs does not appear to increase patient immune responses beyond those generally observed for mAb biotherapeutics.