LC–HRMS quantitation of intact antibody drug conjugate trastuzumab emtansine from rat plasma

Aim: Compared with small molecules, LC–MS quantitation of larger biotherapeutic proteins such as antibodies and antibody–drug conjugates at the intact level presents many challenges in both LC and MS due to their higher molecular weight, bigger size, structural complexity and heterogeneity. Results & conclusion: In this study, quantitation of an intact lysine-linked antibody–drug conjugate, trastuzumab emtansine is presented. Trastuzumab emtansine was extracted from rat plasma using bead-based immunoaffinity capture; after elution from the beads, it was directly analyzed on a LC–HRMS system. Quantitation using both extracted ion chromatogram and deconvoluted mass peaks was evaluated. A limit of quantitation was approximately 20 ng on column with a linear dynamic range from 5 to 100 μg/ml. In addition, the reproducibility and distribution of the drug-to-antibody ratio at different trastuzumab emtansine concentrations were discussed.