Erythropoietin (EPO) and other erythropoiesis-stimulating agents possess a high 
misuse potential in elite sport due to their ability to increase the oxygen 
transport capacity, which plays a vital role in enhancing endurance performance. 
Currently, a new generation of EPO-mimetic peptides is under development from 
which peginesatide (also referred to as Hematide™), a pegylated homodimeric 
peptide of approximately 45 kDa with no structural relationship to 
erythropoietin, is the most advanced drug candidate undergoing phase-III 
clinical trials. Since preventive doping research aims at the development of 
detection methods before a drug receives clinical approval, a selective and 
sensitive assay has to be established knowing that conventional doping control 
assays for EPO will not succeed in detecting peginesatide. Thus, a pegylated 
EPO-mimetic peptide simulating the structure and properties of the lead drug 
candidate peginesatide was synthesised as a model compound for this new class of 
emerging drugs and characterised by means of gel electrophoresis, 
matrix-assisted laser desorption/ionisation (MALDI) mass spectrometry, as well 
as liquid chromatography/electrospray ionisation tandem mass spectrometry 
(LC/ESI-MS/MS) after proteolytic digestion. Based on these results, a mass 
spectrometric detection method of the product in plasma was developed targeting 
a pentapeptide fragment after protein precipitation and subtilisin digestion. 
Its fitness for purpose was evaluated by the determination of selected method 
characteristics focusing particularly on specificity, recovery (ca. 60%), and 
limit of detection (1 ng/mL).