How paediatric drug development and use could benefit from OMICs: A c4c expert group white paper.

The safety and efficacy of pharmacotherapy in children, particularly preterms, neonates and infants, is limited by a paucity of good-quality data from prospective clinical drug trials. A specific challenge is the establishment of valid biomarkers. OMICs technologies may support these efforts by complementary information about targeted and nontargeted molecules through systematic characterization and quantitation of biological samples. OMICs technologies comprise at least genomics, epigenomics, transcriptomics, proteomics, metabolomics and microbiomics in addition to the patient's phenotype. OMICs technologies are in part hypothesis-generating, allowing an in depth understanding of disease pathophysiology and pharmacological mechanisms. Application of OMICs technologies in paediatrics faces major challenges before routine adoption. First, developmental processes need to be considered, including a subdivision into specific age groups as developmental changes clearly impact OMICs data. Second, compared to the adult population, the number of patients is limited as are the type and amount of necessary biomaterial, especially in neonates and preterms. Thus, advanced trial designs and biostatistical methods, noninvasive biomarkers, innovative biobanking concepts including data and samples from healthy children, as well as analytical approaches (eg liquid biopsies) should be addressed to overcome these obstacles. The ultimate goal is to link OMICs technologies with innovative analysis tools, such as artificial intelligence at an early stage. The use of OMICs data based on a feasible approach will contribute to the identification complex phenotypes and subpopulations of patients to improve the development of medicines for children with potential economic advantages.

Effects of angiotensin II receptor blockers on serum levels of epoxyeicosatrienoic acids and dihydroxyeicosatrienoic acids in patients admitted to a cardiovascular center.

PURPOSE: Several clinical studies have demonstrated that angiotensin-converting enzyme inhibitors, but not angiotensin II receptor blockers (ARBs), reduce the risk of non-fatal myocardial infarction and cardiovascular mortality. We found that ARBs inhibited the activity of various cytochrome enzymes in arachidonic acid metabolism, resulting in decreased in vitro production of epoxyeicosatrienoic acids (EETs), which exhibit vasodilation and anti-inflammatory effects, and their subsequent metabolites, dihydroxyeicosatrienoic acids (DHETs). The present study examined the effects of ARBs on serum levels of EETs and DHETs in patients admitted to a cardiovascular center. METHODS: A total of 223 patients were enrolled, of which 107 were exposed to ARBs in this study. ARB-free individuals were defined as the control group (n = 116). Serum levels of EETs and DHETs were measured by liquid chromatography-tandem mass spectrometry. Multiple linear regression analyses were carried out to identify covariates for total serum levels of EETs and DHETs. RESULTS: A significant negative association was observed between ARB use and serum EET and DHET levels (p = 0.034), whereas a significant positive association was observed between the estimated glomerular filtration rate (eGFR) and serum EET and DHET levels (p = 0.007). The median serum total EET and DHET level in the ARB group tended to become lower than that in the control group, although the difference was not significant. CONCLUSION: ARB use and eGFR were significantly associated with total serum levels of EETs and DHETs. Our results suggest that ARBs could affect the concentration of EETs in vivo.

Improved infrastructure and support needed for paediatric clinical trials in Sweden.

AIM: There is a lack of authorised medicines for paediatric patients and improved drug development is necessary. The aim of this study was to evaluate the need for infrastructure and support for paediatric clinical trials in Sweden. METHODS: A web-based survey was sent to doctors and nurses involved in the care of neonates, children and adolescents assessing the current situation and future needs for paediatric clinical trials in Sweden. Questions regarding premises, competence, organisation, support for paediatric clinical trials and Good Clinical Practice Training were addressed. RESULTS: In total, 137 individuals responded to the survey (109 doctors and 28 nurses). Overall, 61% of the respondents had previous experience of paediatric clinical trials. Some respondents had access to trial units, but only 34% had used the trial unit for support. Half of the responders were interested in recurrent paediatric Good Clinical Practice training. Doctors responded that clinical work often had to be prioritised and emphasised the need for research time. CONCLUSION: This study clearly shows the commitment for clinical trials among doctors and nurses involved in paediatric care in Sweden, but also that administrative, logistic and economic support in a sustainable setting and an expanded national collaboration are needed.

Male Anabolic Androgenic Steroid Users with Personality Disorders Report More Aggressive Feelings, Suicidal Thoughts, and Criminality.

Background and objectives: Anabolic androgenic steroids (AAS) are mainly used for aesthetic and performance-enhancing reasons. Their use is a growing public health problem and concern for society because of their adverse effects. The primary aim of this study was to identify psychiatric and personality disorders and to measure anxiety and depression in AAS users. Materials and Methods: Fifty-six males who actively contacted the Anti-Doping Hot-Line and wished to stop using AAS were included. Structured Clinical Interviews Diagnosis-I and -II were used to diagnose psychiatric and personality disorders. The Brief Scale for Anxiety and Montgomery Asberg Depression Rating Scale (subscales from the Comprehensive Psychopathological Rating Scale) were used to measure changes in anxiety and depression. Structured Clinical Interviews Diagnosis-I and -II were performed at one time point. Anxiety and depression were measured at inclusion and after six months. Urine samples were collected for an analysis of AAS and drugs of abuse. Results: All participants reported some adverse effects that they associated with AAS use. In total, 56% and 52% of the cohort fulfilled the criteria for Structured Clinical Interviews Diagnosis-I and -II diagnoses, respectively. A significantly increased risk of reporting aggressive feelings/behaviors (Odds Ratio (OR) = 4.9; Confidence Interval (CI) 0.99-25, p = 0.04), suicidal thoughts/attempts (OR = 4.6, CI 95; 0.99-21, p = 0.04) and criminality (OR = 6.5, CI 1-39, p = 0.03) was found among individuals with AAS use fulfilling the criteria for personality disorders compared with those without such AAS use. The Brief Scale for Anxiety score decreased from the median of 15 at inclusion to 10 at the follow-up visit six months later (p = 0.01, n = 19). Conclusions: Our findings indicate that among individuals with AAS use, those with a personality disorder report more aggressive behaviors, suicidal thoughts/suicidal attempts, and criminality than those without a personality disorder.

Individual variations in fentanyl pharmacokinetics and pharmacodynamics in preterm infants.

AIM: Fentanyl pharmacokinetics and pharmacodynamics are lacking in preterm infants. Our aim was to study these and their relation with a new formulation of fentanyl 5 µg/mL for procedural pain. METHODS: Preterm infants were given 0.5 (n = 20, median gestational age 26.5; range 23.3-34.1 weeks) and 2 µg/kg (n = 8, 27.4; 25.3-30.7 weeks) fentanyl, respectively, before skin-breaking procedures or tracheal intubation. Blood samples were collected after ten minutes, two, four, eight and 24 hours. Physiologic parameters were monitored and pain scores assessed. RESULTS: The median fentanyl concentrations were 0.18, 0.15, 0.15 and 0.57, 0.37, 0.35 ng/mL at 15-31 minutes, two and four hours and the half-lives were 1.6 to 20.5 or 4.1 to 32.6 hours for the low- and high-dose groups, respectively. A significant correlation was seen between weight at study inclusion and half-life (Spearman's r = -0.9, p < 0.001), volume of distribution (r = -0.8, p < 0.01) and clearance (r = -0.9, p < 0.01) in the low-dose group (n = 9). Pain assessment results were not correlated to pharmacokinetic variables. Fentanyl was well tolerated. CONCLUSION: The inter-individual variation of fentanyl pharmacokinetics is large in preterm infants, and the dose of 0.5 µg/kg seems not effective for skin-breaking procedures.

Combined effect of telmisartan and fluvastatin on arachidonic acid metabolism in human liver microsomes.

1. Epoxyeicosatrienoic acids (EETs), metabolites of arachidonic acid (AA) via cytochrome P450s, have a protective effect on the cardiovascular system involving vasodilation. We have previously demonstrated that telmisartan (TEL) inhibits EETs production from AA in vitro. 2. The objectives of the study were to examine the inhibitory effect of fluvastatin (FLU), an inhibitor of CYP2C9, and the combined effect of TEL and FLU on the production of EETs using human liver microsomes. The combined effect of TEL and FLU was evaluated using two methods, the fixed concentration method and the fixed ratio method. 3. FLU significantly reduced total eicosanoids (sum of EETs and their subsequent metabolites dihydroxyeicosatrienoic acids) production at > 0.25 µM. The results of the fixed concentration method indicated that the addition of the other inhibitor resulted in significant reduction of the production of total eicosanoids in a concentration-dependent manner. In the fixed ratio method, the combination of TEL and FLU over all concentration ratios tested did not produce a horizontal shift in the dose response curves. 4. Our results showing an additive combined effect of TEL and FLU on AA metabolism, suggest that concomitant treatment with TEL and FLU would theoretically affect the vascular tone mediated by EETs from AA.

The Inhibitory Effect of Telmisartan on the Metabolism of Arachidonic Acid by CYP2C9 and CYP2C8: An in Vitro Study.

Epoxyeicosatorienoic acids (EETs) are generated from arachidonic acid (AA) by CYPs. EETs comprise four regioisomers (14,15-, 11,12-, 8,9-, and 5,6-EET). EETs show potent physiological effects, including vasodilation, anti-inflammation, myocardial preconditioning, and anti-platelet aggregation effects. We recently demonstrated that telmisartan, one of angiotensin II receptor blockers, inhibits AA metabolism by CYP enzymes, including CYP2C8, CYP2C9, and CYP2J2. We conducted studies of AA metabolism using recombinant CYP enzymes to estimate the inhibition constant and the type of inhibition by telmisartan of CYP2C9 and CYP2C8. The contribution ratio (CR) of each CYP enzyme was investigated using human liver microsomes. Dixon and Lineweaver-Burk plots indicated that telmisartan is a mixed inhibitor of both CYP2C9 and CYP2C8; telmisartan did not show a time-dependent inhibition toward these CYP enzymes. Based on the CRs, both CYP2C9 and CYP2C8 are the key enzymes in the metabolism of AA in the human liver. Uptake of telmisartan in the liver by organic anion transporting polypeptide (OATP) 1B3 and the non-linear metabolism in gastrointestinal tract augment the potential of the drug to inhibit the CYP enzymes in the liver.

Co-administration of Fluvastatin and CYP3A4 and CYP2C8 Inhibitors May Increase the Exposure to Fluvastatin in Carriers of CYP2C9 Genetic Variants.

Fluvastatin, which is one of the hydroxymethylglutaryl-CoA (HMG-CoA) reductase inhibitors (statins), is primarily metabolized by CYP2C9 and to a lesser extent by CYP3A4 and CYP2C8. Predictions of drug-drug interactions (DDI) are important for the safety of combination therapies with statins, in particular drugs that are metabolized by CYP3A4. Little information is available regarding drug interactions with fluvastatin. Since CYP2C9 is a polymorphic enzyme, we investigated the effect of DDI via CYP2C9, CYP3A4, and CYP2C8 on fluvastatin pharmacokinetics by using a validated prediction method in relation to CYP2C9 variants. The predicted increases in the area under the concentration-time curve (AUC) ratios of fluvastatin in carriers with CYP2C9*1/*2, CYP2C9*1/*3, CYP2C9*2/*2, CYP2C9*2/*3, and CYP2C9*3/*3 versus that found in carriers with CYP2C9*1/*1 were 1.16, 1.35, 1.37, 1.65, and 2.06, respectively. Our in silico model predicted that administration of fluvastatin in conjunction with the potent inhibitors that completely inhibited CYP3A4 and CYP2C8 in carriers with the CYP2C9*3/*3 variant would cause a 3.23- and 2.60-fold increase in the AUC ratios, respectively, when compared to that for the carriers with the CYP2C9*1/*1 taking fluvastatin alone. We also predicted the effect of telmisartan when coadministered with fluvastatin. Our prediction results showed that the interaction between telmisartan and fluvastatin via CYP enzymes were negligible in clinical situations.

Genetic Predisposition to Poor Opioid Response in Preterm Infants: Impact of KCNJ6 and COMT Polymorphisms on Pain Relief After Endotracheal Intubation.

BACKGROUND: Single-nucleotide polymorphisms in genes involved in pain control might predispose to exaggerated sensitivity or difference in opioid analgesic effect. The relevance of the KCNJ6 -1250G>A (rs6517442, c.-1787G>A) and the catecholamine-O-methyltransferase (COMT) c.472G>A (rs4680, ValMet) single-nucleotide polymorphisms were studied in preterm infants needing intubation and randomized to a premedication strategy including remifentanil (n = 17) or morphine (n = 17). METHODS: Pain was scored with Astrid Lindgren and Lund Children's Hospital Pain Assessment Scale every 30 minutes for 6 hours. The pain relief provided by the opioids was compared between the different KCNJ6 and COMT genotypes. RESULTS: Infants homozygous for the KCNJ6 -1250A allele had an increased duration after intubation to achieve a score indicating no pain compared with infants with the A/G or G/G genotypes (182 ± 30, 109 ± 29, and 60 ± 21 minutes, respectively; Logrank = 7.5, P = 0.006). Similarly, the duration was increased in individuals with the COMT Val/Val alleles compared with Val/Met and Met/Met (285 ± 37, 137 ± 25, and 63 ± 15 minutes, respectively; Logrank = 14.4, P = 0.0021). Cox proportional hazards analysis confirmed that the variation in both genes was independently associated with susceptibility to respond to therapy. CONCLUSION: We conclude that the KCNJ6 -1250A and COMT Val alleles are predisposing preterm newborns to diminished opioid-induced pain relief.

Statin-induced myopathy in a usual care setting-a prospective observational study of gender differences.

PURPOSE: The study aims to identify the occurrence and remission of statin-induced myopathy including patient perception and symptom characteristics with a gender perspective. METHODS: The study was designed as a prospective, non-interventional investigation in 192 outpatients receiving statin treatment in usual care with 12 months follow-up. Main outcome measure was myopathy related to statin treatment and classified as probable using WHO criteria for adverse drug reaction (ADR) assessment. RESULTS: Fourteen percent developed myopathy, risk ratio for women 1.52 [95 % CI 1.37; 1.66] as compared to men. The majority graded their pain as "severe." CK values were within normal range. Eighty percent of the women compared to 43 % of the men reported that the muscular symptoms affected their daily life activities to a moderate or severe extent. For those who stopped treatment, mypopathy was the reason for 70 % of the women and 25 % of the men. There was a difference in mean dose between men with and without myopathy, but not in women. Among the patients with myopathy, 76 % reported other ADRs as compared to 21 % of the patients without myopathy (p = 0.002). Twenty-nine percent of the women and 18 % of the men reported other ADRs. CONCLUSION: Women reported a higher frequency of myopathy and other ADRs as well as a larger impact on daily life activities. In men, but not in women, the risk of myopathy was dose-dependent. Patients with myopathy were more susceptible to other statin-induced ADRs which raises the question about common underlying mechanisms.

Effects of Angiotensin II Receptor Blockers on Metabolism of Arachidonic Acid via CYP2C8.

Arachidonic acid (AA) is metabolized to epoxyeicosatrienoic acids (EETs) via cytochrome enzymes such as CYP 2C9, 2C8 and 2J2. EETs play a role in cardioprotection and regulation of blood pressure. Recently, adverse reactions such as sudden heart attack and fatal myocardial infarction were reported among patients taking angiotensin II receptor blockers (ARBs). As some ARBs have affinity for these CYP enzymes, metabolic inhibition of AA by ARBs is a possible cause for the increase in cardiovascular events. In this study, we quantitatively investigated the inhibitory effects of ARBs on the formation of EETs and further metabolites, dihydroxyeicosatrienoic acids (DHETs), from AA via CYP2C8. In incubations with recombinant CYP2C8 in vitro, the inhibitory effects were compared by measuring EETs and DHETs by HPLC-MS/MS. Inhibition of AA metabolism by ARBs was detected in a concentration-dependent manner with IC50 values of losartan (42.7 µM), telmisartan (49.5 µM), irbesartan (55.6 µM), olmesartan (66.2 µM), candesartan (108 µM), and valsartan (279 µM). Losartan, telmisartan and irbesartan, which reportedly accumulate in the liver and kidneys, have stronger inhibitory effects than other ARBs. The lower concentration of EETs leads to less protective action on the cardiovascular system and a higher incidence of adverse effects such as sudden heart attack and myocardial infarction in patients taking ARBs.

Simultaneous Determination Method of Epoxyeicosatrienoic Acids and Dihydroxyeicosatrienoic Acids by LC-MS/MS System.

Epoxyeicosatrienoic acids (EETs) are produced primarily by CYPs from arachidonic acid (AA) and then further metabolized to the corresponding dihydroxyeicosatrienoic acids (DHETs). EETs play important roles in physiological processes such as regulating vasodilation and inflammation. Thus, the drug inhibition of CYP-mediated AA metabolism could reduce production of EETs, potentially resulting in adverse cardiovascular events. The aim of this study was to develop a simple method to simultaneously determine the concentrations of both EETs and DHETs using a conventional LC-MS/MS system to evaluate drug-endogenous substance interactions, including eicosanoids. Eight eicosanoids (5,6-EET, 8,9-EET, 11,12-EET, 14,15-EET, 5,6-DHET, 8,9-DHET, 11,12-DHET, and 14,15-DHET) were detected with their corresponding deuterium-labeled eicosanoids as internal standards. The samples were purified by solid-phase extraction columns. Liquid chromatographic separation was achieved on a C18 column. DHETs and EETs were eluted at 4-7 and 18-26 min, respectively. The weighted (1/y(2)) calibration curves were linear over a range of 5-2000 nmol/L for EETs and 2-2000 nmol/L for DHETs. In quality control (QC) samples, the recoveries of eicosanoids were 95.2-118%. The intra-day precisions were within 6% in all three QC samples, and the inter-day precisions were <16.7% at 50 nmol/L, <8.6% at 200 nmol/L, and <9.8% at 1000 nmol/L. We have applied this method for the determination of the eicosanoid levels in samples from incubation studies of AA by using human recombinant CYP enzyme (rCYP), and confirmed that the method has sensitivity sufficient for assessment of rCYP incubation study.

Losartan competitively inhibits CYP2C8-dependent paclitaxel metabolism in vitro.

The present study aimed to characterize the inhibitory effects of losartan, an angiotensin II receptor blocker, on CYP2C8. Inhibition experiments were based on human lymphoblast-expressed recombinant CYP2C8 (rCYP2C8) and paclitaxel as a CYP2C8 substrate. The disappearance of paclitaxel (initial concentration: 7.5 µmol/L) was monitored over time at different concentrations of losartan (0, 100, 500 and 1000 µmol/L). For Dixon and Cornish-Bowden plots, various concentrations of losartan (final concentration: 0, 50, 100 and 250 µmol/L) and paclitaxel (final concentration: 3.75, 7.5 and 15 µmol/L) were used. Losartan exhibited significant inhibitory effects on paclitaxel disappearance at losartan concentrations of ≥100 µmol/L (p<0.05). Losartan at 50 µmol/L inhibited the disappearance of paclitaxel by about 60%. Both plots showed that losartan exerted competitive inhibition of rCYP2C8, and its apparent Ki value was estimated to be 40.7 µmol/L. The degree of inhibition (R value) for rCYP2C8 after oral administration of losartan (100 mg) was estimated to be 1.2, using the maximum hepatic input total blood concentration (7.3 µmol/L). The present results show that losartan acts as a competitive inhibitor of CYP2C8-dependent drug metabolism in vitro. Subjects with a low clearance of losartan, resulting in a high average systemic blood concentration of losartan after repeated oral administration, should be carefully monitored for possible adverse reactions during co-medication with CYP2C8 substrate drugs.

Expression of UGT2B7 is driven by two mutually exclusive promoters and alternative splicing in human tissues: changes from prenatal life to adulthood and in kidney cancer.

OBJECTIVE: UDP-glucuronosyltransferase 2B7 (UGT2B7) plays a major detoxification role in commonly prescribed drugs and endogenous lipophilic molecules. Additional exons and multiple alternative splicing events (ASEs) at the UGT2B7 locus were recently discovered. MATERIALS AND METHODS: Novel and classical ASEs were quantified in 27 human tissues, as well as in fetal and tumoral tissues. The activity of the alternative UGT2B7 promoters was studied in cell lines. RESULTS: UGT2B7 expression is driven by an alternate promoter 1a associated with transcripts containing exon 1b, which is located ∼44 kb upstream of the known promoter 1 associated with transcripts containing exon 1 required for enzyme activity. The exon 1 was expressed most abundantly in the liver and gastrointestinal tract, whereas exon 1b was expressed predominantly in other extrahepatic tissues. Experimental evidence indicated endogenous translation that yields alternative UGT2B7s derived from the use of exon 1b are enzymatically inactive. Alternate 5' ASE predominates in fetal tissues (kidney, lung) and kidney tumor samples compared with normal adult kidney. These changes further correlate with reduced glucuronidation in neoplastic kidneys. This differential expression pattern was further confirmed using four liver and kidney cell lines and was consistent with the differential usage of alternate promoters in hepatic (promoter 1) and kidney cells (1a). CONCLUSION: UGT2B7 is characterized by two mutually exclusive exons 1, both flanked by a unique 5' promoter region. Data also indicated a switch toward functional enzyme upon maturation in the kidney and reversal of this process in neoplastic cells, considerably modifying the glucuronidation potential across human tissues and cells.

Tissue distribution and relative gene expression of UDP-glucuronosyltransferases (2B7, 2B15, 2B17) in the human fetus.

UDP-glucuronosyltransferases (UGTs) catalyze phase II conjugation reactions and play an important role in the inactivation and elimination of several drugs. It is well known that the UGT activity in fetal livers is low compared with the UGT activity in adult livers. In this study the mRNA expression levels of the three human subfamilies, 2B7, 2B15, and 2B17, were determined in 20 adult and 60 fetal liver tissue specimens. The expression profile in fetal kidneys (N = 43), adrenals (N = 46), and lungs (N = 37) was also determined. All fetal and adult samples were genotyped for the UGT2B17 deletion polymorphism. Adult liver contained 13-36 times higher levels of UGT2B mRNAs as compared with fetal livers. UGT2B7 was most abundant in fetal lungs and kidneys, whereas UGT2B15 and UGT2B17 were predominant in the liver. There was a significant correlation between UGT2B7 expression levels in lungs and kidneys, whereas for the other UGT2Bs no correlation between the different tissues was observed. Fetuses expressing two UGT2B17 alleles (ins/ins) displayed significantly higher levels of UGT2B17 mRNA compared to ins/del fetuses in lungs, whereas in the other tissues no gene dose-effect was observed.

Atorvastatin treatment induces uptake and efflux transporters in human liver.

The metabolism and disposition of statins are highly dependent on different cytochrome P450 enzymes, such as CYP3A4 and CYP2C9, as well as membrane transporters SLCO1B1, SLCO2B1, ABCB1, and ABCG2. Interindividual gene expression differences among these enzymes may explain part of the variability in tolerance and effect for statin treatment. The aim of the present study was to investigate the effect of statin treatment on these genes in human liver tissue. Levels of CYP3A4, CYP2C9, SLCO1B1, SLCO2B1, ABCB1, and ABCG2 mRNA in liver tissue from a previously performed clinical trial in 29 patients randomized to treatment with placebo, 80 mg/day of atorvastatin, or 20 mg/day of fluvastatin for 4 weeks were measured using quantitative polymerase chain reaction. Treatment with atorvastatin (n = 10), but not with fluvastatin (n = 10), resulted in 3-fold higher expression of SLCO2B1 compared with placebo-treated patients (n = 9) (P < 0.05). Atorvastatin increased the expression of both ABCB1 and ABCG2 by more than 2-fold (P < 0.05). No difference was found in CYP2C9, CYP3A4, or SLCO1B1 mRNA expression in patients administered statins or those administered placebo. Premenopausal women (n = 8) had higher expression of CYP3A4 (P < 0.05) and lower expression of CYP2C9 (P < 0.05) compared with postmenopausal women (n = 10) and men (n = 11), respectively. Here we show for the first time that atorvastatin treatment leads to increased expression of the membrane transporters SLCO2B1, ABCB1, and ABCG2 in human liver tissue, which potentially may counteract the efficacy of the treatment, and our findings may cast light on the mechanisms of clinical problems with adverse reactions and drug interactions in statin treatment.

Testosterone challenge and androgen receptor activity in relation to UGT2B17 genotypes.

BACKGROUND: We investigated the androgen receptor (AR) bioluminescense response in serum and urine before and after testosterone challenge in different genotypes of the UGT2B17 enzyme, which catalyses testosterone glucuronidation. MATERIAL AND METHODS: The androgen receptor activity was determined using a yeast-based bioluminescence assay. The androgens were analysed using LC-MS/MS, and the individuals were genotyped for UGT2B17 deletion polymorphism using real-time polymerase chain reaction. RESULTS: The serum concentrations of testosterone and dihydrotestosterone (DHT) were markedly elevated on days 2 and 4 and were still above baseline on day 15 after a dose of 500 mg testosterone enanthate. The androgenic activity in serum increased in parallel and correlated with the hormone concentrations and remained above baseline on day 15. The urinary androgenic activity increased 4-5-fold and was closely related to the unconjugated testosterone and independent of the UGT2B17 genotype. CONCLUSIONS: The AR assay may serve as a complement to the urinary testosterone/epitestosterone (T/E) doping test, because this is profoundly influenced by the UGT2B17 deletion polymorphism. It may also be useful for detection of other illicit androgens in sports, or in the society, or for monitoring and diagnostics of androgen-related disorders.