Determination of drug-to-antibody ratio of antibody-drug conjugate in biological samples using microflow-liquid chromatography/high-resolution mass spectrometry.

Drug-to-antibody ratio (DAR), payload release and metabolite profile of deconjugated payload-linker of vorsetuzumab maleimidocaproyl valine-citrulline p-aminobenzyloxycarbonyl monomethyl auristatin E, an antibody­drug conjugate (ADC) with cleavable linker and monomethyl auristatin E as payload, are reported. Species-specific retention of DAR, payload release and metabolite patterns of deconjugated payload-linker of the ADC are summarized. Exploring the fate of payload-linker moieties deconjugated from ADCs in the body is also vital to understanding pharmacological activity and toxicity. Species-specific metabolite patterns of the ADC provided insight into the importance of optimization of the payload-linker moiety in biological samples, especially in humans. In terms of a more sensitive analytical platform for drug metabolism and pharmacokinetic evaluation, microflow-liquid chromatography/high-resolution mass spectrometry (LC­HRMS) in DAR analysis was found to take advantage of the improvement of detection sensitivity compared with conventional LC­HRMS. Because ADCs are a complex drug modality, these results indicated the importance of evaluation of ADCs from a drug metabolism and pharmacokinetics point of view to understand the pharmacology and toxicology of ADCs, more precisely.