title: Identification of selected in vitro generated phase-I metabolites of the steroidal selective androgen receptor modulator MK-0773 for doping control purposes.
abstract: Research into developing anabolic agents for various therapeutic purposes has been pursued for decades. As the clinical utility of anabolic-androgenic steroids has been found to be limited because of their lack of tissue selectivity and associated off-target effects, alternative drug entities have been designed and are commonly referred to as selective androgen receptor modulators (SARMs). While most of these SARMs are of nonsteroidal structure, the drug candidate MK-0773 comprises a 4-aza-steroidal nucleus. Besides the intended therapeutic use, SARMs have been found to be illicitly distributed and misused as doping agents in sport, necessitating frequently updated doping control analytical assays. As steroidal compounds reportedly undergo considerable metabolic transformations, the phase-I metabolism of MK-0773 was simulated using human liver microsomal (HLM) preparations and electrochemical conversion. Subsequently, major metabolic products were identified and characterized employing liquid chromatography-high-resolution/high- accuracy tandem mass spectrometry with electrospray (ESI) and atmospheric pressure chemical ionization (APCI) as well as nuclear magnetic resonance (NMR) spectroscopy. MK-0773 produced numerous phase-I metabolites under the chosen in vitro incubation reactions, mostly resulting from mono- and bisoxygenation of the steroid. HLM yielded at least 10 monooxygenated species, while electrochemistry-based experiments resulted predominantly in three monohydroxylated metabolites. Elemental composition data and product ion mass spectra were generated for these analytes, ESI/APCI measurements corroborated the formation of at least two N-oxygenated metabolites, and NMR data obtained from electrochemistry-derived products supported structures suggested for three monohydroxylated compounds. Hereby, the hydroxylation of the A-ring located N- bound methyl group was found to be of particular intensity. In the absence of controlled elimination studies, the produced information enables the implementation of new target analytes into routine doping controls and expands the focus of anti-doping efforts concerning this new anabolic agent.
authors.affiliation: Bayer CropScience AG, Alfred-Nobel-Str. 50, 40789 Monheim, Germany. andreas.lagojda@bayer.com.
authors.forename: Andreas
authors.initials: A
authors.lastname: Lagojda
authors.affiliation: Bayer CropScience AG, Alfred- Nobel-Str. 50, 40789 Monheim, Germany. dirk.kuehne@bayer.com.
authors.forename: Dirk
authors.initials: D
authors.lastname: Kuehne
authors.affiliation: Center for Preventive Doping Research - Institute of Biochemistry, German Sport University Cologne, Am Sportpark Müngersdorf 6, 50933 Cologne, Germany. European Monitoring Center for Emerging Doping Agents, Cologne/Bonn, Germany. o.krug@biochem.dshs-koeln.de.
authors.forename: Oliver
authors.initials: O
authors.lastname: Krug
authors.affiliation: Center for Preventive Doping Research - Institute of Biochemistry, German Sport University Cologne, Am Sportpark Müngersdorf 6, 50933 Cologne, Germany. a.thomas@biochem.dshs-koeln.de.
authors.forename: Andreas
authors.initials: A
authors.lastname: Thomas
authors.affiliation: Westfälische Wilhelms-Universität Münster, Institute of Inorganic and Analytical Chemistry, Corrensstr. 30, 48419 Münster, Germany. tina.wigger@uni-muenster.de.
authors.forename: Tina
authors.initials: T
authors.lastname: Wigger
authors.affiliation: Westfälische Wilhelms- Universität Münster, Institute of Inorganic and Analytical Chemistry, Corrensstr. 30, 48419 Münster, Germany. uk@uni-muenster.de.
authors.forename: Uwe
authors.initials: U
authors.lastname: Karst
authors.affiliation: Center for Preventive Doping Research - Institute of Biochemistry, German Sport University Cologne, Am Sportpark Müngersdorf 6, 50933 Cologne, Germany. schaenzer@dshs-koeln.de.
authors.forename: Wilhelm
authors.initials: W
authors.lastname: Schänzer
authors.affiliation: Center for Preventive Doping Research - Institute of Biochemistry, German Sport University Cologne, Am Sportpark Müngersdorf 6, 50933 Cologne, Germany. European Monitoring Center for Emerging Doping Agents, Cologne/Bonn, Germany. thevis@dshs-koeln.de.
authors.forename: Mario
authors.initials: M
authors.lastname: Thevis
mesh_terms: D045930:Anabolic Agents; D000728:Androgens; D004300:Doping in Sports; D006801:Humans; D006900:Hydroxylation; D011944:Receptors, Androgen; D021241:Spectrometry, Mass, Electrospray Ionization; D015813:Substance Abuse Detection
chemical_list: D045930:Anabolic Agents; D000728:Androgens; D011944:Receptors, Androgen