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

Analytical advances in horseracing medication and doping control from 2018 to 2023

The analytical approaches taken by laboratories to implement robust and efficient regulation of horseracing medication and doping control are complex and constantly evolving. Each laboratory's approach will be dictated by differences in regulatory, economic and scientific drivers specific to their local environment. However, in general, laboratories will all be undertaking developments and improvements to their screening strategies in order to meet new and emerging threats as well as provide improved service to their customers. In this paper, the published analytical advances in horseracing medication and doping control since the 22nd International Conference of Racing Analysts and Veterinarians will be reviewed. Due to the unprecedented impact of COVID-19 on the worldwide economy, the normal 2-year period of this review was extended to over 5 years. As such, there was considerable ground to cover, resulting in an increase in the number of relevant publications included from 107 to 307. Major trends in publications will be summarised and possible future directions highlighted. This will cover developments in the detection of 'small' and 'large' molecule drugs, sample preparation procedures and the use of alternative matrices, instrumental advances/applications, drug metabolism and pharmacokinetics, the detection and prevalence of 'endogenous' compounds and biomarker and OMICs approaches. Particular emphasis will be given to research into the potential threat of gene doping, which is a significant area of new and continued research for many laboratories. Furthermore, developments in analytical instrumentation relevant to equine medication and doping control will be discussed.

In silico and in vitro human metabolism of IOX2, a performance-enhancing doping agent

IOX2 is a potent inhibitor of prolyl hydroxylase 2, a key enzyme in the regulation of hypoxia-inducible factor (HIF) and oxygen homeostasis. As such, it can be used to enhance athletic performance and is currently banned by the World Anti-Doping Agency (WADA). Detection of metabolites is critical to demonstrate drug use in doping. However, there is currently little data on IOX2 human metabolism. Our aim was to identify relevant biomarkers of IOX2 use in humans. For this purpose, IOX2 was incubated with 10-donor-pooled human hepatocytes for 3 h, incubates were analyzed by liquid chromatography-high-resolution tandem mass spectrometry (LC-HRMS/MS), and LC-HRMS/MS data were screened with Compound Discoverer (Thermo Scientific) for a comprehensive identification of IOX2 metabolites. Additionally, IOX2 human metabolites were predicted with GLORYx open-access software (University of Hamburg, Germany) to assist in the LC-HRMS/MS analysis and data mining. Thirteen metabolites were identified, oxidation at the quinolinyl group, O-glucuronidation, and combinations being predominant biotransformations. The results were consistent with previous animal studies and a single case of oral microdose administration. We suggest hydroxyquinolinyl-IOX2 as major biomarker of IOX2 use in biological samples, glucuronide hydrolysis being critical to increase IOX2 and hydroxyquinolinyl-IOX2 detectability in urine.

Comprehensive metabolic investigation of dopamine reuptake inhibitor HDMP-28 in equine liver microsomes and Cunninghamella elegans for doping control

A dopamine reuptake inhibitor is a type of medication or substance that works by blocking the reuptake of dopamine in the brain. Dopamine reuptake inhibitors offer multiple effects, including increased alertness, improved mood, and therapeutic potential for conditions like depression, ADHD, and Parkinson's disease. HDMP-28, or methylnaphthidate, is a potent synthetic stimulant from the phenyltropane class. It surpasses methylphenidate in both dopamine reuptake inhibition and half-life. As a dopamine reuptake inhibitor, it boosts dopamine levels by hindering reuptake into nerve cells, resulting in heightened stimulation and increased energy. In order to comprehensively address both the tangible and potential repercussions of the unauthorized utilization of the aforementioned substance in sports, it is imperative to establish analytical methodologies for the identification of the parent drug and its primary metabolites. Additionally, a comprehensive analysis of the metabolic characteristics of HDMP-28 in both human and animal subjects has yet to be published. This study explores the metabolic conversion of HDMP-28 mediated by equine liver microsomes and Cunninghamella elegans. An extraction and detection method was developed, optimized, and validated for doping assessment in equine urine and plasma. Liquid chromatography-high-resolution mass spectrometry was employed to determine metabolite structures. The study identified 31 (22 phase I and 9 phase II) metabolites of HDMP-28, including hydroxylated, hydrogenated, and hydrolyzed analogs. Glucuronic acid-conjugated metabolites were also detected. This manuscript describes metabolites based on the in vitro studies, which might not be the same in vivo. These findings aid in the detection and understanding of the illicit use of HDMP-28 in equestrian sports.

Effects of radiation therapy on tumor microenvironment: an updated review

ABSTRACT

Cancer is a major threat to human health and causes death worldwide. Research on the role of radiotherapy (RT) in the treatment of cancer is progressing; however, RT not only causes fatal DNA damage to tumor cells, but also affects the interactions between tumor cells and different components of the tumor microenvironment (TME), including immune cells, fibroblasts, macrophages, extracellular matrix, and some soluble products. Some cancer cells can survive radiation and have shown strong resistance to radiation through interaction with the TME. Currently, the complex relationships between the tumor cells and cellular components that play major roles in various TMEs are poorly understood. This review explores the relationship between RT and cell-cell communication in the TME from the perspective of immunity and hypoxia and aims to identify new RT biomarkers and treatment methods in lung cancer to improve the current status of unstable RT effect and provide a theoretical basis for further lung cancer RT sensitization research in the future.

Investigation of in vitro generated metabolites of LGD-4033, a selective androgen receptor modulator, in homogenized camel liver for anti-doping applications

RATIONALE

The use of selective androgen receptor modulators (SARM) in sports is prohibited by the World Anti-Doping Agency (WADA) due to their potential as performance-enhancing drugs, offering an unfair advantage. LGD-4033 is a SARM known for its similarities to anabolic steroids and can be easily purchased online, leading to increased availability and misuse. Adverse analytical findings have revealed the presence of SARMs in dietary supplements. Although LGD-4033 misuse has been reported in human sports over the years, concerns also arise regarding its illicit use in animal sports, including camel racing. Although various studies have investigated the metabolism of LGD-4033 in humans, horse, and other species, there is limited research specifically dedicated to racing camels.

METHODS

This study focuses on the in vitro metabolism of LGD-4033 in homogenized camel liver using liquid chromatography-high-resolution mass spectrometry (LC-HRMS) to identify and characterize the metabolites.

RESULTS

The findings indicated the presence of 12 phase I metabolites and 1 phase II metabolite. Hydroxylation was responsible for the formation of the main phase I metabolites that were identified. A glucuronic acid conjugate of the parent drug was observed in this study, but no sulfonic acid conjugate was found. The possible chemical structures of these metabolites, along with their fragmentation patterns, were identified using MS.

CONCLUSIONS

These findings provide valuable insights into the metabolism of LGD-4033 in camels and aid in the development of effective doping control methods for the detection of SARMs in camel racing.

Metabolic study of selective androgen receptor modulator LY2452473 in thoroughbred horses for doping control

RATIONALE

Since 2010, there has been an increasing number of adverse analytical findings related to selective androgen receptor modulators (SARMs) in competitive sports. It emphasizes the importance of comprehensive doping control analytical procedures that are capable of detecting SARM misuse.

METHODS

In this study, it is described how LY2452473, a SARM, was metabolized in thoroughbred horses after a single-dose oral administration and in vitro with equine liver microsome preparations. An investigation of the metabolism of LY2452473 in horses' urine, plasma, and hair matrices was carried out during the study. The plausible structures of the detected metabolites were postulated using high-performance liquid chromatography-high resolution mass spectrometry.

RESULTS

Under the experimental conditions 15 metabolites (12 phase I and three conjugates of phase I) were detected (M1-M15). The major phase I metabolites identified were formed by hydroxylation. Side-chain dissociated and methylated metabolites were also detected. In phase II, the glucuronic acid and sulfonic acid conjugates of hydroxy LY2452473 were detected as the major metabolites. In vitro analysis has confirmed the presence of all metabolites found in vivo except for the methylated analogs M11 and M12. A peak concentration of LY2452473 (0.5 pg/mg) in proximal hair segments was achieved 4 weeks after administration, according to hair analysis.

CONCLUSIONS

Data obtained will aid in identifying LY2452473 and related substances faster. Furthermore, the results will assist in checking for the illegal use of these substances in competitive sports.

Investigation of in vitro generated metabolites of GLPG0492 using equine liver microsomes for doping control

An effective alternative to testosterone therapy is selective androgen receptor modulators, a class of compounds that has a tissue-specific effect on muscle and bone. These drugs, which enhance performance, pose a severe abuse risk in competitive sports. GLPG0492 is one of the selective androgen receptor modulators discovered in recent decades. This compound has a unique tissue-specific action for muscle and bone against steroid receptors and acts as a partial agonist for androgen receptors. This study examined GLPG0492 and its metabolites in vitro using equine liver microsomes. Liquid chromatography-high-resolution mass spectrometry was utilized to determine the probable structures of detected metabolites. This study identified 39 metabolites of GLPG0492 (21 phase I and 18 phase II). The hydroxylation of GLPG0492 results in monohydroxylated and dihydroxylated metabolites. Additionally, the study detected dissociated side chains (3-methyl and 4-(hydroxymethyl)) and corresponding hydroxylated metabolites. A series of glucuronic acid- and sulfonic acid-conjugated analogs of GLPG0492 were detected during phase II of the study. The findings might help in the detection of GLPG0492 and the elucidation of its illegal use in equestrian sports.

Identification of in vitro metabolites of boldenone using Camel liver microsomes – A HR-LCMS approach

Anabolic steroids are widely abused in animal sports to improve their performance. The present study identifies the possible metabolites of boldenone in camel liver. A high-resolution accurate QE mass spectrometer was used to identify the parent boldenone and its metabolites. To investigate the phase 1 biotransformation of boldenone in camel, sodium phosphate buffer and NADPH were used. Chromatographic separation was carried out on a Thermo Hypersil C18 column using acetonitrile and formic acid as mobile phases. The current study, helped in unequivocal detection of six metabolites (Phase 1) for boldenone. The 17b-boldenone is an 3-oxo-Delta (1), Delta(4)-steroid substituted by an oxo group at position 3 and a beta-hydroxy group at position 17. It is prone to oxidation, which results in three hydroxylated metabolites with protonated parent ion of m/z 303.1954 (C19H27O3)+. Androsta-1,4-diene-3,17-dione [M+H]+ of m/z 285.1848 (C19H25O2+), hydroxyandrosta-1,4-diene-3,17-dione [M+H]+ of m/z 301.1797 (C19H25O3+) in addition to 17-hydroxy-androsta-1-en-3-one [M+H]+ of m/z 289.2162 (C19H29O2+) were also identified. The structures of the detected metabolites were identified based on their accurate mass, fragmentation pattern, and chromatographic retention time. In this research, camel liver was successfully used for in vitro experiments as an alternative to liver microsomes.

Pharmacokinetic Study of Vadadustat and High-Resolution Mass Spectrometric Characterization of its Novel Metabolites in Equines for the Purpose of Doping Control

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.

Long-term monitoring of IOX4 in horse hair and its longitudinal distribution with segmental analysis using liquid chromatography/electrospray ionization Q Exactive high-resolution mass spectrometry for the purpose of doping control

IOX4, a hypoxia-inducible factor stabilizer, is classified as a banned substance for horses in both horse racing and equestrian sports. We recently reported the pharmacokinetic profiles of IOX4 in horse plasma and urine and also identified potential monitoring targets for the doping control purpose. In this study, a long-term longitudinal analysis of IOX4 in horse hair after a nasoesophageal administration of IOX4 (500 mg/day for three days) to three thoroughbred mares is presented for the first time for controlling the abuse/misuse of IOX4. Six bunches of mane hair were collected at 0 (pre), 1, 2, 3, and 6 month(s) post-administration. Our results showed that the presence of IOX4 was identified in all post-administration horse hair samples but no metabolite could be detected. The detection window for IOX4 could achieve up to 6-month post-administration (last sampling point) by monitoring IOX4 in hair. In order to evaluate the longitudinal distribution of IOX4 over six months, a validated quantification method of IOX4 in hair was developed for the analysis of the post-administration samples. Segmental analysis of 2-cm cut hair across the entire length of post-administration hair showed that IOX4 could be quantified up to the level of 1.84 pg/mg. In addition, it was found that the movement of the incorporated IOX4 band in the hair shaft over six months varied among the three horses due to individual variation and a significant diffusion of IOX4 band up to 10 cm width was also observed in the 6-month post-administration hair samples.

Characterization of equine liver microsome-generated metabolites of growth hormone secretagogue small molecule ibutamoren

RATIONALE

Interest in growth hormone secretagogues has intensified during the past several years based on capable, ever-widening investigational applications of recombinant growth hormone in animals and humans. Ibutamoren is a potent, long-acting, selective and orally active non-peptide growth hormone secretagogue, which has a great potential for abuse as a performance-enhancing agent in sports.

METHODS

To support drug metabolism and pharmacokinetic studies of chiral pharmaceuticals, it is necessary to combine the resolving power of high-performance liquid chromatography with the sensitivity of mass spectrometric techniques. This paper describes the metabolic conversion of ibutamoren using equine liver microsomes and metabolite characterization using a QExactive high-resolution mass spectrometer.

RESULTS

A total of 32 metabolites for ibutamoren (20 phase I and 12 phase II) were detected. The important findings of the current research are as follows: (1) the growth hormone secretagogue ibutamoren was prone to oxidation, resulting in corresponding hydroxylated metabolites; (2) in ibutamoren, the dissociation of the phenyl ring and 2-amino-2-methylpropanamide side chain was also observed; (3) the glucuronic acid conjugates of mono-, di- and trihydroxylated analogues were detected; and (4) no sulfonic acid conjugated metabolites were observed in this study of ibutamoren.

CONCLUSIONS

The reported data help in the speedy detection of the growth hormone secretagogue ibutamoren and reveal its illegal use in competitive sports.

In vitro studies of hypoxia inducible factor-prolyl hydroxylase inhibitors daprodustat, desidustat, and vadadustat for equine doping control

Performance-enhancing substances and methods have become a serious problem in competitive sports. The hypoxia-inducible factor (HIF) stabilizers can enhance the organism's capacity for molecular oxygen transport and are likely to be abused as performance-enhancing agents in sports. This paper describes the metabolic conversion of the popular hypoxia inducible factor-prolyl hydroxylase (HIF-PH) inhibitors, namely, daprodustat, desidustat, and vadadustat using equine liver microsomes, determined on a QExactive high-resolution mass spectrometer. During this study, a total of 10 metabolites for daprodustat (all are Phase I), 10 metabolites for desidustat (five each for Phase I and Phase II), and 15 metabolites for vadadustat (six for Phase I and nine for Phase II) were detected. The important findings of the current research are as follows: (1) All the three HIF-PH inhibitor drug candidates are prone to oxidation, which results in corresponding hydroxylated metabolites; (2) in desidustat, hydrolysis and dissociation of oxime linkage also observed; (3) the glucuronic acid conjugate (except daprodustat) of the parent drugs as well as the monohydroxylated analogs were observed; (4) sulfonic acid conjugated metabolites were observed only for vadadustat.

Comprehensive metabolic study of IOX4 in equine urine and plasma using liquid chromatography/electrospray ionization Q Exactive high-resolution mass spectrometer for the purpose of doping control

IOX4 is a hypoxia-inducible factor prolyl hydroxylase (HIF-PHD) inhibitor, which was developed for the treatment of anemia by exerting hematopoietic effects. The administration of HIF-PHD inhibitors such as IOX4 to horses is strictly prohibited by the International Federation of Horseracing Authorities and the Fédération Équestre Internationale. To the best of our knowledge, this is the first comprehensive metabolic study of IOX4 in horse plasma and urine after a nasoesophageal administration of IOX4 (500 mg/day, 3 days). A total of four metabolites (three mono-hydroxylated IOX4 and one IOX4 glucuronide) were detected from the in vitro study using homogenized horse liver. As for the in vivo study, post-administration plasma and urine samples were comprehensively analyzed with liquid chromatography/electrospray ionization high-resolution mass spectrometry to identify potential metabolites and determine their corresponding detection times. A total of 10 metabolites (including IOX4 glucuronide, IOX4 glucoside, O-desbutyl IOX4, O-desbutyl IOX4 glucuronide, four mono-hydroxylated IOX4, N-oxidized IOX4, and N-oxidized IOX4 glucoside) were found in urine and three metabolites (glucuronide, glucoside, and O-desbutyl) in plasma. Thus, the respective quantification methods for the detection of free and conjugated IOX4 metabolites in urine and plasma with a biphase enzymatic hydrolysis were developed and applied to post-administration samples for the establishment of elimination profiles of IOX4. The detection times of total IOX4 in urine and plasma could be successfully prolonged to at least 312 h.

Olympic anti-doping laboratory: the analytical technological road from 2016 Rio De Janeiro to 2021 Tokyo

The summer Olympic Games is the major mega sports event since the first modern era Olympiad, held in Athens, Greece in 1896. International Olympic Committee (IOC) has the responsibility of the organization of the summer and winter Games ensuring the broadcast in all corners of earth. The World Anti-Doping Agency (WADA) is the responsible organization of the fight against doping in sports. IOC and WADA support the event's country WADA Accredited Laboratory to incorporate the maximum of the new analytical technologies to become applicable during the event's antidoping testing. The current study reviewed the last 5 years progresses of the antidoping system with emphasis on the laboratory field.