Title:Pharmacokinetic Study of Vadadustat and High-Resolution Mass Spectrometric
Characterization of its Novel Metabolites in Equines for the Purpose of Doping
Control
Volume: 23
Issue: 10
Author(s): Hideaki Ishii*, Mariko Shibuya, Kanichi Kusano, Yu Sone, Takahiro Kamiya, Ai Wakuno, Hideki Ito, Kenji Miyata, Fumio Sato, Taisuke Kuroda, Masayuki Yamada and Gary Ngai-Wa Leung
Affiliation:
- Drug Analysis Department, Laboratory of Racing Chemistry, 1731-2 Tsuruta-machi, Utsunomiya, Tochigi, Zip 320-0851, Japan
- Department of Pharmaceutical Sciences, Tohoku University Hospital, 1-1 Seiryo-machi, Aoba-ku, Sendai, Miyagi, Zip 980-8574,
Japan
Keywords:
Vadadustat, HIF stabilizer, doping control, equine, metabolic study, LC/ESI-HRMS.
Abstract:
Background: Vadadustat, a hypoxia-inducible factor prolyl hydroxylase (HIF-PHD) inhibitor, is a substance
which carries a lifetime ban in both horse racing and equestrian competition. A comprehensive metabolic
study of vadadustat in horses has not been previously reported.
Objective: Metabolism and elimination profiles of vadadustat in equine plasma and urine were studied for the purpose
of doping control.
Methods: A nasoesophageal administration of vadadustat (3 g/day for 3 days) was conducted on three thoroughbred
mares. Potential metabolites were comprehensively detected by differential analysis of full-scan mass spectral data
obtained from both in vitro studies with liver homogenates and post-administration samples using liquid chromatography
high-resolution mass spectrometry. The identities of metabolites were further substantiated by product ion
scans. Quantification methods were developed and validated for the establishment of the excretion profiles of the
total vadadustat (free and conjugates) in plasma and urine.
Results: A total of 23 in vivo and 14 in vitro metabolites (12 in common) were identified after comprehensive analysis.
We found that vadadustat was mainly excreted into urine as the parent drug together with some minor conjugated
metabolites. The elimination profiles of total vadadustat in post-administration plasma and urine were successfully
established by using quantification methods equipped with alkaline hydrolysis for cleavage of conjugates such as
methylated vadadustat, vadadustat glucuronide, and vadadustat glucoside.
Conclusion: Based on our study, for effective control of the misuse or abuse of vadadustat in horses, total vadadustat
could successfully be detected for up to two weeks after administration in plasma and urine.