Method for predicting human intestinal first-pass metabolism of UGT substrate compounds

1. As intestinal glucuronidation has been suggested to generate the low oral bioavailability (F) of drugs, estimating its effects would be valuable for selecting drug candidates. Here, we investigated the absorption and intestinal availability (F_aF_g) in animals, and intrinsic clearance via UDP-glucuronosyltransferase (UGT) in intestinal microsomes (CL_int,UGT) for three drug candidates possessing a carboxylic acid group, in an attempt to estimate the impact of intestinal glucuronidation on F and select potential drug candidates with high F in humans.

2. The F_aF_g values of the three test compounds were low in rats and monkeys (0.16–0.51), and high in dogs (≥0.81). Correspondingly, the CL_int,UGT values were high in rats and monkeys (101–731 µL/min/mg), and low in dogs (≤?59.6 µL/min/mg). A good inverse correlation was observed between F_aF_g and CL_int,UGT, suggesting that intestinal glucuronidation was a major factor influencing F_aF_g of these compounds.

3. By applying this correlation to F_aF_g in humans using human CL_int,UGT values (26.9–114 µL/min/mg), compounds 1–3 were predicted to have relatively high F_aF_g.

4. Our approach is expected to be useful for estimating the impact of intestinal glucuronidation on F in animals and semiquantitatively predicting human F for drug candidates.

     

In vitro and in vivo metabolism and detection of 3‐HO‐PCP,a synthetic phencyclidine,in human samples and pooled human hepatocytes using high resolution mass spectrometry

The new psychoactive substance (NPS) 3‐HO‐PCP, a phencyclidine (PCP) analog, was detected in a law enforcement seizure and in forensic samples in Denmark. Compared with PCP, 3‐HO‐PCP is known to be a more potent dissociative NPS, but no toxicokinetic investigations of 3‐HO‐PCP are yet available. Therefore, 3‐HO‐PCP was quantified in in vivo samples, and the following were investigated: plasma protein binding, in vitro and in vivo metabolites, and metabolic targets. All samples were separated by liquid chromatography and analyzed by mass spectrometry. The unbound fraction in plasma was determined as 0.72 ± 0.09. After in vitro incubation with pooled human hepatocytes, four metabolites were identified: a piperidine‐hydroxyl‐and piperidine ring opened N‐dealkyl‐COOH metabolite, and O‐glucuronidated‐ and O‐sulfate‐conjugated metabolites. In vivo, depending on the sample and sample preparation, fewer metabolites were detected, as the O‐sulfate‐conjugated metabolite was not detected. The N‐dealkylated‐COOH metabolite was the main metabolite in the deconjugated urine sample. in vivo analytical targets in blood and brain samples were 3‐HO‐PCP and the O‐glucuronidated metabolite, with 3‐HO‐PCP having the highest relative signal intensity. The drug levels of 3‐HO‐PCP quantified in blood were 0.013 and 0.095 mg/kg in a living and a deceased subject, respectively. The 3‐HO‐PCP concentrations in deconjugated urine in a sample from a living subject and in post‐mortem brain were 7.8 and 0.16 mg/kg, respectively. The post mortem results showed a 1.5‐fold higher concentration of 3‐HO‐PCP in the brain tissue than in the post mortem blood sample.     

In-depth metabolic study of nonsteroidal selective androgen receptor modulator GSK2881078 in thoroughbred horses and horse liver microsomes for doping control

Nonsteroidal selective androgen receptor modulators (SARMs) are a novel class of compounds that have not yet been clinically approved; however, they appear to have a better anabolic/androgenic ratio than steroids and cause slighter side effects. Sports drug testing laboratories are required to maintain continuously updated doping control analytical methods in light of the widespread misuse of SARMs in elite and amateur sports. This paper describes the metabolic conversion of SARM GSK2881078 in thoroughbred horses following oral administration and in vitro with equine liver microsomes. A liquid chromatography–high-resolution mass spectrometry method was used to postulate the plausible structures of the detected metabolites. A total of five (M1–M5) in vivo metabolites and six (M1–M6) in vitro metabolites were detected under experimental conditions. Phase I metabolites mainly result from hydroxylation. Methoxylated and side-chain dissociated metabolites were also detected. Neither sulfonic acid nor glucuronic acid conjugated metabolites were observed in this study. Data reported here could aid in the detection of nonsteroidal SARM GSK2881078 and reveal its illicit use in competitive sports.     

Pharmacokinetics and metabolism of a sulphamide NK2 antagonist in rat,dog and human

1. UK-224,671 is a sulphamide-containing NK₂ antagonist with moderate lipophilicity and basicity. 2. The physicochemical properties of UK-224,671 are reflected in its pharmacokinetics following intravenous (i.v.) administration. The compound partitioned extensively into red blood cells in all species examined and the blood clearance was moderate to low with respect to liver blood flow and distribution into tissues was extensive. 3. UK-224,671 exhibited species differences in oral bioavailability. In dog, the compound exhibited moderate bioavailability (55%), whereas in rat and man oral bioavailability was < 10%. 4. In rat and dog, the major excreted form after i.v. administration was unchanged UK224,671 in both urine and faeces. In addition, of three metabolites observed, the most abundant was the N-descyclopropylmethyl (UK-280,045). 5. The profile of radioactivity in rat following oral administration of [¹⁴C]-UK-224,671 was not consistent with a 10% absorbed compound with 40% of the dose present as metabolites. This suggests that the low bioavailability of UK-224,671 in rat is due to a combination of moderate intestinal permeability and extensive first-pass metabolism by the gut and does not result from poor gastrointestinal absorption per se.     

Liver size and indices of drug metabolism in alcoholics

Summary The role of liver size in drug metabolism was investigated in 34 chronic alcoholics and 28 controls by comparing antipyrine half-life with biopsy content and total amount of hepatic cytochrome P-450 (P-450) and liver weight. Liver size was significantly greater in alcoholics than in controls. Total P-450 was increased and antipyrine metabolism was enhanced in alcoholics with normal histology of the liver. In subjects with alcoholic hepatitis or cirrhosis, the antipyrine half-life was prolonged and P-450 was decreased. Alcoholics with fatty liver had a reduced P-450 content, but the total amount of P-450 and the antipyrine half-life were normal. The results demonstrate in alcoholics that an enlarged liver of normal histological appearance is associated with enhanced drug metabolism. In subjects with fatty liver the drug metabolizing capacity per unit weight of liver is often impaired, but the increase in liver size leads to undisturbed total oxidizing capacity and normal in vivo metabolism. In alcoholic hepatitis drug metabolism is impaired in spite of hepatomegaly. In cirrhosis the enlargement of the liver appears to compensate for the decreased P-450 content resulting in only slightly decreased total P-450, and the severely impaired in vivo drug metabolism may be due to derangement of blood flow.     

Organ-on-a-chip: Determine feasibility of a human liver microphysiological model to assess long-term steroid metabolites in sports drug testing

A fundamental challenge in preventive doping research is the study of metabolic pathways of substances banned in sport. However, the pharmacological predictions obtained by conventional in vitro or in vivo animal studies are occasionally of limited transferability to humans according to an inability of in vitro models to mimic higher order system physiology or due to various species-specific differences using animal models. A more recently established technology for simulating human physiology is the “organ-on-a-chip” principle. In a multichannel microfluidic cell culture chip, 3-dimensional tissue spheroids, which can constitute artificial and interconnected microscale organs, imitate principles of the human physiology. The objective of this study was to determine if the technology is suitable to adequately predict metabolic profiles of prohibited substances in sport. As model compounds, the frequently misused anabolic steroids, stanozolol and dehydrochloromethyltestosterone (DHCMT) were subjected to human liver spheroids in microfluidic cell culture chips. The metabolite patterns produced and circulating in the chip media were then assessed by LC-HRMS/(MS) at different time points of up to 14 days of incubation at 37°C. The overall profile of observed glucurono-conjugated stanozolol metabolites excellently matched the commonly found urinary pattern of metabolites, including 3′OH-stanozolol-glucuronide and stanozolol-N-glucuronides. Similarly, but to a lower extent, the DHCMT metabolic profile was in agreement with phase-I and phase-II biotransformation products regularly seen in postadministration urine specimens. In conclusion, this pilot study indicates that the “organ-on-a-chip” technology provides a high degree of conformity with traditional human oral administration studies, providing a promising approach for metabolic profiling in sports drug testing.     

Reliability of human cryopreserved hepatocytes and liver microsomes as in vitro systems to predict metabolic clearance

A total of 110 drugs, selected to cover a range of physicochemical and pharmacokinetic properties, were used to explore standard approaches to the prediction of in vivo metabolic clearance using drug-depletion profiles from human liver microsomes (HLMs) and cyropreserved hepatocytes. A total of 41 drugs (37% of the compounds tested) showed measurable depletion rates using HLMs (depletion by 20% or more over the time course). The most reliable correlations in terms of bias (average fold error (AFE) = 2.32) and precision (root mean square error (RMSE) = 3501) were observed by comparing in vivo intrinsic clearance (CL_int), calculated using the parallel-tube model and incorporating the fraction unbound in blood, with in vitro CL_int adjusted for microsomal binding. For these reference drugs, 29% of predictions were within two-fold of the observed values and 66% were within five-fold. Compared with HLMs, clearance predictions with cryopreserved hepatocytes (57 drugs) were of similar precision (RMSE = 3608) but showed more bias (AFE = 5.21) with 18% of predictions within two-fold of the observed values and 46% within five-fold. However, with a broad complement of drug-metabolizing enzymes, hepatocytes catalysed measurable CL_int values for a greater proportion (52%) of the reference compounds and were particularly proficient at defining metabolic rates for drugs with predominantly phase 2 metabolic routes.     

The effects of UDP-sugars,UDP and Mg2+on uridine diphosphate glucuronosyltransferase activity in human liver microsomes

1. The UDP-glucuronosyltransferase (UGT) enzymes are important in the metabolism, elimination and detoxification of many xenobiotics and endogenous compounds. As extrapolation of in vitro kinetics of drug metabolizing enzymes to predict in vivo clearance rates becomes more sophisticated, it is important to ensure proper optimization of enzyme assays. The luminal location of the enzyme active site (i.e. latency), and the complexity of UGT kinetics, results in consistent under-prediction of clearance of drugs metabolized by glucuronidation.

2. We examined inhibition of UGT activity in alamethicin-disrupted human liver microsomes (HLM) by uridine diphosphate (UDP), a UGT reaction product, and its reversal by Mg²⁺ ions. We also determined whether UDP-sugars other than the co-substrate UDP-glucuronic acid (UDP-GlcA) affected glucuronidation.

3. We show that other UDP-sugars do not significantly influence glucuronidation. We also demonstrate that UDP inhibits HLM UGT activity and that this is reversed by including Mg²⁺ in the assay. The Mg²⁺ effect can be offset using EDTA, and is dependent on the concentration of UDP-GlcA in the assay.

4. We propose that formation of a Mg²⁺–UDP complex prevents UDP from affecting the enzyme. Our results suggest that 5?mM UDP-GlcA and 10?mM Mg²⁺ be used for UGT assays in fully disrupted HLM.     

Characterization of the Phase II metabolites of rutaecarpine in rat by liquid chromatography-electrospray ionization-tandem mass spectrometry

From the authors’ previous studies on the Phase I metabolism of rutaecarpine, nine metabolites formed were identified as products of hydroxylation on the aromatic rings in rat liver microsomes. In order to determine the possible metabolic fate of rutaecarpine, the Phase II metabolites of rutaecarpine were characterized in the present study by using liquid chromatography/electrospray ionization-tandem mass spectrometry (LC/ESI-MS). When male Sprague–Dawley rats were treated intravenously with 4?mg?kg^?1 rutaecarpine, 16 different Phase I and II metabolites were identified in urine including four sulfate and four glucuronide conjugates. Phase I metabolites of rutaecarpine were identified as four mono-hydroxylated metabolites (M2–5) and four isobaric di-hydroxylated metabolites (M6–9). These metabolites were identical to the in vitro metabolites except one, which was hydroxylated in the aliphatic moiety. In addition, Phase II metabolites were identified as conjugated with sulfate (S1–4) and glucuronide (G1–4). In faeces, 11 different metabolites were identified. The metabolites M8 and glucuronide conjugated (G1–4) were not detected. Structures of all metabolites were confirmed with CID fragmentation spectra of MS², MS³ and retention times by LC/ESI-MS.     

Venoconstrictor responses to ergosine and ergosinine: Evidence for the isomerization of ergosinine

Ergosine and its D-isolysergic acid derivative ergosinine were investigated on canine saphenous veins both in vivo and in vitro. Following local i.v. infusion in vivo, about 5 times higher doses of ergosinine were necessary to produce the same venoconstrictor response as induced by ergosine. When administered orally, however, both ergot alkaloids were equi-effective. In vitro methiothepin, a 5-HT receptor blocker with high affinity for 5-HT₁ receptors, antagonized venoconstrictor responses to 5-HT and ergosine within the same concentration range, being significantly less potent when tested against norepinephrine. The reverse was true for the α₂-selective adrenoceptor blocker yohimbine, which was significantly more potent against norepinephrine and ergosine than against 5-HT, suggesting that ergosine has affinity to both 5-HT₁-like receptors and α₂-adrenoceptors. Concentration-response curves to norepinephrine were shifted to the right in a parallel fashion when ergosine or ergosinine were present in the organ baths, suggesting competitive antagonism. The blocking potency of ergosinine increased with increasing incubation times in Krebs-Henseleit solution becoming similar to that of ergosine when an incubation time of 2 hr was applied. It is suggested that the pharmacological activity of ergosinine is the consequence of an isomerization into its natural stereoisomer ergosine, which may occur both in vivo and in vitro.     

Intestinal phase-II metabolism of quercetin in HT29 cells, 3D human intestinal tissues and in healthy volunteers: a qualitative comparison using LC-IMS-MS and LC-HRMS

1. Flavonoids are a large class of dietary molecules, among which quercetin is the most ubiquitous, which undergo an extensive intestinal phase-II metabolism. We compared the in vivo metabolism of quercetin in healthy volunteers with two in vitro models, HT29 cells and 3?D human intestinal tissues. Supernatants of the in vitro experiments and the human intestinal fluids (HIF) were analyzed by LC-IMS-MS and LC-HRMS in a qualitative way.

2. Quercetin glucuronides, sulfates and their methyl conjugates were detected in all three systems. The metabolic profiles were found to be different, both in terms of the metabolites produced and their relative proportions. In particular, quercetin sulfates were almost absent in supernatants from HT29 cells incubations while they were a major metabolite in HIF and also found in 3?D intestinal tissues incubations.

3. IMS provided structural information as well as a third dimension of characterization, while HRMS brought increased sensitivity and MS/MS confirmation. HT29 cells are a useful tool to generate phase-II metabolites but do not represent the in vivo situation. 3?D intestinal tissues appear as a more relevant tool to study the intestinal phase-II metabolism of flavonoids.

     

Structural elucidation of in vitro metabolites of bavachinin in rat liver microsomes by LC-ESI-MSn and chemical synthesis

1.?Bavachinin isolated from Psoralea corylifolia has various activities, such as antimicrobial, antiallergic, antitumor and so on. Our previous study showed that natural bavachinin exhibits peroxisome proliferator-activated receptor γ-agonist activity.

2.?In vitro studies on bavachinin metabolism were conducted using rat liver microsomes incubated at 37?°C for 60?min.

3.?Structures of eight metabolites of the incubation mixtures were cautiously characterized using electrospray tandem mass spectra and three synthetic compounds. The results indicated that eight metabolites of bavachinin were biotransformed mainly through oxidation.

4.?The metabolic pathways of bavachinin were elucidated in vitro. These results contribute to the understanding of bavachinin’s in vivo metabolism.     

液相色谱-串联质谱法在药物代谢研究中应用最新进展

液相色谱-质谱联用技术因其具有高分离能力、高灵敏度、应用范围广和较强的专属性等特点,已成为一种重要的现代分离分析技术。串联质谱法比单极质谱具有更高的灵敏度和选择性,可以得到更多的结构信息。本文首先介绍了液相色谱-串联质谱法中串联质谱基本原理、常见质谱质量分析器及其特点、串联质谱的连接方式和数据采集方法等。然后将其在药物代谢研究中的主要应用作简要介绍,主要包括利用串联质谱测定药物的代谢动力学参数,利用几种串联质谱应用方式对药物代谢物的结构进行鉴定,概括了每种方式的优劣,总结了串联质谱在药物代谢物结构鉴定中的应用策略,并对其在药物代谢未来的应用进行了展望。     

In vitro and in vivo glucuronidation of midazolam in humans

AIMS

Midazolam (MDZ) is a benzodiazepine used as a CYP3A4 probe in clinical and in vitro studies. A glucuronide metabolite of MDZ has been identified in vitro in human liver microsome (HLM) incubations. The primary aim of this study was to understand the in vivo relevance of this pathway.

METHODS

An authentic standard of N-glucuronide was generated from microsomal incubations and isolated using solid-phase extraction. The structure was confirmed using proton nuclear magnetic resonance (NMR) and ¹H-¹³C long range correlation experiments. The metabolite was quantified in vivo in human urine samples. Enzyme kinetic behaviour of the pathway was investigated in HLM and recombinant UGT (rUGT) enzymes. Additionally, preliminary experiments were performed with 1′-OH midazolam (1′-OH MDZ) and 4-OH-midazolam (4-OH MDZ) to investigate N-glucuronidation.

RESULTS

NMR data confirmed conjugation of midazolam N-glucuronide (MDZG) standard to be on the α-nitrogen of the imidazole ring. In vivo, MDZG in the urine accounted for 1–2% of the administered dose. In vitro incubations confirmed UGT1A4 as the enzyme of interest. The pathway exhibited atypical kinetics and a substrate inhibitory cooperative binding model was applied to determine K_m (46 µM, 64 µM), V_max (445 pmol min⁻¹ mg⁻¹, 427 pmol min⁻¹ mg⁻¹) and K_i (58 µM, 79 µM) in HLM and rUGT1A4, respectively. From incubations with HLM and rUGT enzymes, N-glucuronidation of 1′-OH MDZ and 4-OH MDZ is also inferred.

CONCLUSIONS

A more complete picture of MDZ metabolism and the enzymes involved has been elucidated. Direct N-glucuronidation of MDZ occurs in vivo. Pharmacokinetic modelling using Simcyp™ illustrates an increased role for UGT1A4 under CYP3A inhibited conditions.     

CYP450s体外重组技术及在药物代谢和安全性评价中的应用

药物代谢是在代谢酶催化下完成的 ,它决定着药物的药理学和毒理学特性。根据动物实验来预测人体的药物代谢时 ,代谢酶的种属差异性会使这项研究工作变得非常困难。本文对含有人体代谢酶系的重组技术模型的应用进行了介绍和评价。从而有助于预测新药在人体中的代谢机制     

Human phase-I metabolism and prevalence of two synthetic cannabinoids bearing an ethyl ester moiety: 5F-EDMB-PICA and EDMB-PINACA

Around 2017, with the appearance of 5F-EDMB-PINACA, synthetic cannabinoids (SCs) carrying an ethyl ester moiety at the linked group started spreading on the market of new psychoactive substances (NPS). In 2020 and 2021, the indole analog of 5F-EDMB-PINACA (5F-EDMB-PICA) and the non-fluorinated analog of this compound (EDMB-PINACA) were analytically characterized. Here, we present suitable urinary markers to prove the consumption of these two ethyl analogs. Ten authentic urine samples for each compound were analyzed by liquid chromatography–quadrupole time-of-flight mass spectrometry (LC-qToF-MS). Anticipated phase-I metabolites detected in urine samples were confirmed in vitro by applying a pooled human liver microsomes (pHLM) assay. Prevalence data were obtained from urines collected for abstinence control and submitted to a screening method for SC metabolites. Ten phase-I metabolites of 5F-EDMB-PICA and 18 of EDMB-PINACA were detected by LC-qToF-MS analysis of authentic urine specimens. The main in-vivo metabolites were built by ester hydrolysis, often coupled to further metabolic processes. Investigation of phase-I biotransformation led to the identification of ester hydrolysis, monohydroxylation, and defluorination products as the most suitable urinary biomarkers for 5F-EDMB-PICA. Metabolites formed by ester hydrolysis coupled to ketone formation and by monohydroxylation are suggested for the detection of EDMB-PINACA. From October 1, 2020 to February 1, 2022, among positive urine samples, 5.4% and 10.1% tested positive 5F-EDMB-PICA and EDMB-PINACA, respectively. Due to common metabolites shared among structurally related SCs, the unequivocal detection of their consumption remains challenging for forensic laboratories and requires sensitive methods to monitor multiple metabolites, ideally including highly specific species.     

美洛昔康片溶出度考察及其体内外相关性

目的:考察2种市售美洛昔康片的体外溶出度,评价其质量及其体内外相关性.方法:采用转篮法测定溶出度,计算累积溶出百分率并与体内吸收百分率进行相关性评价;用Weibull分布模型对溶出曲线进行拟合,提取溶出参数并进行统计分析.结果:2种美洛昔康片的溶出参数之间差异有非常显著意义(P＜0.01).t检验表明同一厂家3批产品的参数之间差异有时也有显著性(P＜0.05).2种片剂的体外溶出与体内吸收之间均具有显著相关性.结论:2个厂家产品的溶出度之间存在差异并且体内外具有相关性,提示在临床用药时应加以注意.     

托特罗定联合奥昔布宁治疗膀胱过度活动症的疗效及对患者焦虑评分的影响

目的：观察托特罗定联合奥昔布宁治疗膀胱过度活动症的疗效,关注治疗后患者焦虑评分,以期为临床工作提供帮助。方法选取医院收治的144例膀胱过度活动症患者作为研究对象,应用随机区组的原则分为观察组和对照组各72例,对照组应用托特罗定进行治疗,观察组应用托特罗定联合奥昔布宁进行治疗,观察治疗效果。同时应用焦虑自评量表评价治疗后患者的焦虑评分。结果观察组总有效率为98．61％明显高于对照组的90．28％,且治疗后焦虑评分明显低于对照组,差异均有统计学意义（P＜0．05）。结论托特罗定联合奥昔布宁治疗膀胱过度活动症患者的疗效明显,同时能更有效地减少患者的焦虑情绪,临床治疗中可以积极应用。     

盐酸氨溴索缓释片体内外相关性研究

目的考察盐酸氨溴索缓释片体外释放度与体内吸收的相关性。方法应用释放度测定法研究盐酸氨溴索缓释片体外释药行为 ,采用HPLC法测定盐酸氨溴索缓释制剂在家犬体内的血药浓度 ,按照Wagner Nelson公式计算药物的吸收分数。 结果 3种自制盐酸氨溴索缓释片与参比制剂生物等效 ,以药物累积吸收百分数 f(t)与相应时刻的体外累积释放百分数F(t)建立的一元线性回归方程 ,参比制剂与 3种自制制剂的体内外相关系数分别为 0 969、0 979、0 970和 0 983。结论盐酸氨溴索缓释片的体外释放度与体内吸收具有显著的相关性。