Bioanalytics – Chemical
The last decade has seen a rise of new protein-based biotherapeutic modalities, extending well beyond simple IgG monoclonal antibodies to multidomain and hybrid molecular constructs. Antibody drug conjugates (ADCs) are prime example of complex hybrid molecules, consisting of a large molecule ‘delivery’ component conjugated with small molecule ‘drug’ components, that are designed for highly targeted therapies. Because ADCs are generally heterogenous and dynamically undergo changes in vivo, bioanalysis is challenging and multiple assays are needed to support pharmacokinetic studies. Three PK assays are typically employed: Total Antibody, Conjugated Antibody or Antibody-Conjugated Drug (or Total ADC), and Unconjugated Drug to evaluate exposure-response relationships for efficacy and safety, as well as to gain insight into biotransformation and disposition in terms of deconjugation and elimination. In addition, pharmacokinetic assessment may require monitoring of circulating target receptor proteins and co-administered biotherapeutics. This talk will focus on bioanalytical strategies to improve efficiency for ADC bioanalysis, while measuring multiple species of interest, using hybrid LC-MS/MS technology. A case study will be presented wherein a single assay was used to simultaneously quantify total antibody and antibody-conjugated drug from an ADC, comprising of a biparatopic antibody linked to tubulysin analogue through a cleavable linker, in human matrix using hybrid LC-MS/MS. The talk will conclude with a review of how multiplexed LC-MS/MS assays can address the bioanalytical challenges posed by newer multi-component constructs such as probody-drug conjugates.