A universal surrogate peptide to enable LC-MS/MS bioanalysis of a diversity of human monoclonal antibody and human Fc-fusion protein drug candidates in pre-clinical animal studies.

For the development of human antibody Fc (fraction crystallizable) region-containing therapeutic protein candidates, which can be either monoclonal antibodies (mAbs) or pharmacologically active proteins/peptides fused to the Fc region of human Immunoglobulin G (IgG), reliable quantification of these proteins in animal pharmacokinetic study plasma samples is critical. LC-MS/MS has emerged as a promising assay platform for this purpose. LC-MS/MS assays used for bioanalysis of human antibody Fc region-containing therapeutic protein candidates frequently rely upon quantification of a 'signature' surrogate peptide whose sequence is unique to the protein analyte of interest. One drawback of the signature peptide approach is that a new LC-MS/MS assay must be developed for each new human Fc region-containing therapeutic protein. To address this issue, we propose an alternative 'universal surrogate peptide' approach for the quantification of human antibody Fc region-containing therapeutic protein candidates in plasma samples from all nonclinical species. A single surrogate tryptic peptide was identified in the Fc region of most human antibody Fc-containing therapeutic protein candidates. An LC-MS-MS method based upon this peptide was shown to be capable of supporting bioanalysis of a diversity of human Fc region-containing therapeutic protein candidates in plasma samples of all commonly used animal species.