Bioanalytics – Chemical
2019 PharmSci 360
Myostatin (MSTN) is a negative regulator of skeletal muscle growth and a variety of molecular modalities targeting MSTN are under development, all utilizing circulating MSTN as a target engagement and PD biomarker. We describe a novel reagent-free LC-MS/MS assay to accurately measure circulating MSTN, which overcomes multiple issues associated with ligand-binding assay. Briefly, serum proteins are directly digested by trypsin after denaturation and the resulting peptides were subjected to two-dimensional LC separation to enrich surrogate peptide for subsequent MRM-MS quantitation. The method circumvents the need for antibody reagent for immunocapture of the analyte and eliminates the interferences by therapeutic drug and MSTN binding proteins. Substantial enhancements in the assay sensitivity and selectivity are achieved by the online 2D-LC separation, allowing accurate and precise measurement of 2.5 ng/mL MSTN in animal and human serum. We demonstrate MSTN is an important target engagement and PD biomarker to monitor therapeutic progress.