Detection of the myostatin-neutralizing antibody Domagrozumab in serum by means of Western blotting and LC-HRMS

The TGF-beta cytokine myostatin is considered to be one of the key regulators of skeletal muscle mass. Consequently, specific inhibitors of the growth factor and its signaling pathways are promising therapeutics for the treatment of muscle wasting disorders as well as potential performance-enhancing agents in sports. Domagrozumab is a humanized monoclonal antibody that neutralizes the circulating cytokine, thus preventing receptor activation. Within this study, two complementary detection assays for Domagrozumab from serum were developed by using ammonium sulfate precipitation and immunoaffinity purification either in combination with tryptic digestion and LC-HRMS or Western blotting. While the LC-HRMS assay is highly specific for diagnostic peptides originating from both the heavy and the light chain of the antibody, the second assay is capable of generically detecting intact therapeutic proteins comprising a human Fc domain and exhibiting high specificity for dimeric myostatin/GDF-11. Following optimization, both assays were comprehensively characterized. They can readily be modified to include further protein drugs and will expand the range of available tests for emerging myostatin inhibitors.