Metabolic profile characterization of voxelotor in human urine based on in vivo and in vitro models for doping control

Voxelotor was approved for the treatment of sickle cell anemia as a potent hemoglobin S polymerization inhibitor. Owing to its ability to affect blood components and its potential to enhance athletic performance, voxelotor was included in the prohibited list issued by the World Anti-Doping Agency in 2023, banning its use both in and out of competition. This study aimed to comprehensively investigate the metabolic profile of voxelotor in human urine and identify suitable metabolites for long-term analytical retrospectivity in doping control. A novel strategy for metabolite identification was established by combining in vivo human administration with isotope labeling-based in vitro metabolism analysis. A single microdose of voxelotor was administered orally to five volunteers, and urine samples were collected for up to 28 days post-administration. Concurrently, in vitro incubation of human liver microsomes with voxelotor and D3-voxelotor was conducted, and the microsomal incubates were analyzed via liquid chromatography-high-resolution mass spectrometry. Targeted metabolite searches in human urine samples and automated nontargeted screening of isotope metabolite ion pairs in incubation samples led to the discovery of 9 phase I metabolites and 23 phase II metabolites. Analysis of the urine excretion curves revealed that 4 metabolites, along with voxelotor, were suitable for long-term anti-doping monitoring, with a detection window exceeding 20 days. Using both in vivo and in vitro metabolic models, this study provides comprehensive insight into the metabolic profile of voxelotor in human urine for the first time, enhancing the capacity for doping screening and extending the retrospectivity of voxelotor detection.

Doping control; Long-term metabolites; Mass spectrometry; Metabolic profile; Voxelotor.