Detection and method validation of peginesatide in human serum by means of LC-MS/MS

Erythropoiesis-stimulating agents (ESAs) have frequently been confessed to be illicitly used in elite sports due to their endurance enhancing effects. Recently, peginesatide, the first representative of a new generation of ESAs, referred to as Erythropoietin (EPO)-mimetic peptides, obtained approval in the USA under the trade name Omontys® for the treatment of anemic patients on dialysis. Lacking sequence homology with EPO, it consists of a pegylated homodimeric peptide of approximately 45 kDa, and thus, specific approaches for the determination of peginesatide in blood had to be developed as conventional detection assays for EPO would not succeed in detecting the EPO-mimetic peptides. Therefore, a mass spectrometric detection method in human serum was developed targeting a proteotypic pentapeptide fragment after protein precipitation, subtilisin digestion, and cation-exchange purification. Eventually, the method was validated for qualitative purposes and proved to be specific, sensitive (limit of detection 1 ng/mL), and both precise and linear over a wide range of expected blood concentrations. Thus, the assay not only demonstrated its fitness for purpose for an application in routine doping control analysis but also allows for a detection of therapeutic doses of peginesatide in human serum for approximately one week when considering plasma maximum concentrations of about 1,000 ng/mL after a single intravenous administration of 0.05 mg/kg bodyweight to healthy volunteers and an observed half-live of around one day. Verf.-Referat