Metabolic studies of hypoxia-inducible factor stabilisers IOX2, IOX3 and IOX4 (in vitro) for doping control

Metabolic studies of hypoxia-inducible factor stabilisers IOX2, IOX3 and IOX4 (in vitro) for doping control / Moses Philip, Binoy Mathew, Tajudheen K. Karatt, Zubair Perwad, Michael Benedict Subhahar, Abdul Khader Karakka Kal. - (Drug Testing and Analysis (2021) 17 January)

  • PMID: 33458935
  • DOI: 10.1002/dta.3000


The transcriptional activator hypoxia-inducible factor (HIF) is a vital arbitrator in the performance of cellular responses lacking oxygen supply in aerobic organisms. Because these compounds are capable of enhancing the organism's capacity for molecular oxygen transport, they possess great potential for abuse as a performance-enhancing agent in sports. A comprehensive study of the metabolic conversion of the most popular HIF stabilisers such as IOX2, IOX3 and IOX4 using equine liver microsomes (in vitro) is reported. The parents and their metabolites were identified and characterised by liquid chromatography-mass spectrometry in negative ionisation mode using a QExactive high-resolution mass spectrometer. Under the current experimental condition, a total of 10 metabolites for IOX2 (three phase I and seven phase II), nine metabolites for IOX3 (four phase I and five phase II) and five metabolites for IOX4 (three phase I and two phase II) were detected. The outcome of the present study is as follows: (1) all the three IOX candidates are prone to oxidation, results in subsequent monohydroxylated, and some dihydroxylated metabolites. (2) Besides oxidation, there is a possibility of hydrolysis and de-alkylation, which results in corresponding carboxylic acid and amide, respectively. (3) The glucuronide and sulphate conjugate of the parent drugs as well as the monohydroxylated analogues were observed in this study. The characterised in vitro metabolites can potentially serve as target analytes for doping control analysis.


Research / Study
17 January 2021
Karakka Kal, Abdul Khader
Karatt, Tajudheen K.
Mathew, Binoy
Perwad, Zubair
Philip, Moses
Subhahar, Michael Benedict
United Arab Emirates
Equestrian (FEI) - International Equestrian Federation
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United Arab Emirates Central Veterinary Research Laboratory
Analytical aspects
Animal doping
Mass spectrometry analysis
Testing method development
Doping classes
S2. Peptide Hormones, Growth Factors
Hypoxia-inducible factor (HIF) activating agents
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18 March 2021
Date of last modification
30 March 2021
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