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 mu g/ml. In addition, the reproducibility and distribution of the drug-to-antibody ratio at different trastuzumab emtansine concentrations were discussed.