Multiplex LCMS Bioanalysis of Brentuximab Vedotin, Rituximab and Cetuximab towards Therapeutic Drug Monitoring Application by Combined Calibration Curve Using Fab-Selective Limited Proteolysis nSMOL

Background: Recently, monoclonal antibody (mAb) bioanalysis using mass spectrometry has begun to be recognized as useful technology for mAbs measurement other than ELISA. We have recently exploited a high-precision method for bioanalysis of monoclonal antibody (mAb) using mass spectrometry. The method is nano-surface and molecular-orientation limited (nSMOL) proteolysis, which is useful for LCMS bioanalysis of many kinds of antibody drugs. Methods: nSMOL is Fab-selective limited proteolysis which consists of the difference of protease nanoparticle diameter (200 nm) and antibody resin pore diameter (100 nm). For limited proteolysis of antibody, Protein A resin (pore: 100 nm) slurry was added to plasma including monoclonal antibody, and the antibody Fc region was immobilized to the resin at 25°C for 10 min with gentle vortexing. Antibody-immobilized resin was washed with PBS, and limited proteolysis was performed with trypsin-conjugated FG beads (diameter: 200 nm). Limited proteolysis of Fab region on antibody was achieved by these two diameter difference. After nSMOL proteolysis, the generated peptides were collected by only simple filtration. Results: In this study, we have demonstrated that the first full validation dataset for bioanalysis using nSMOL of antibody-drug conjugate (ADC), Brentuximab vedotin, in human plasma using nSMOL proteolysis. Full validation using nSMOL proteolysis fulfilled criteria of guideline on bioanalytical method validation in pharmaceutical development for small molecule drug compounds. Conclusions: These results indicate that nSMOL is also significant method for precise quantification of ADC in plasma, such as Brentuximab vedotin. Furthermore, we report that nSMOL proteolysis is able to apply for not only singleanalyte but also multi-analyte bioanalysis of each mAbs in plasma, so that, nSMOL proteolysis is feasible multiplex bioanalysis for many clinical pharmacokinetic study and therapeutic drug monitoring.