Long‐Term Excretion of Roxadustat in Urine

ABSTRACTRoxadustat (FG‐4592), an orally active hypoxia‐inducible factor prolyl hydroxylase stabilizer, has been shown to enhance erythropoiesis by increasing endogenous erythropoietin. It is indicated for the treatment of anemia and chronic kidney disease and is approved for clinical use in several countries, including the European Union, Japan and others. Due to its reasonably anticipated performance‐enhancing effect in athletes, roxadustat is prohibited for use in sports at all times. A few cases of adverse analytical findings in routine doping controls have been reported worldwide, some of which were claimed to be the result of contaminated dietary supplements. The present study offers new data demonstrating the long‐term excretion pattern of roxadustat. Even after a single‐dose administration, roxadustat can remain detectable in urine for 8 months, albeit at very low concentrations (<10 pg/mL). Following three times a week treatment with 70 to 100 mg of roxadustat, the drug was still detectable in the urine of anemic patients for between 9 and 18 months after treatment was discontinued. Lastly, an athlete who admitted use of roxadustat for almost a year (50 mg 3 to 5 times a week) has now tested positive multiple times over the course of 15 months (the first test being 12 months after the drug was discontinued), with an estimated concentration of roxadustat between 3 and 8 pg/mL. Altogether, these findings indicate the unusually prolonged terminal excretion kinetics of roxadustat, a property that testing authorities should consider in their results management process.