Pharmacokinetic characterization of carnosol from rosemary (Salvia Rosmarinus) in male C57BL/6 mice and inhibition profile in human cytochrome P450 enzymes.

Rosemary (Salvia Rosmarinus) is a rich source of dietary diterpenes with carnosol as one of the major polyphenols used to standardize rosemary extracts approved as a food preservative, however, at present there is not any information on the murine pharmacokinetic profile of carnosol or its potential for drug interactions. The present study utilizes cell-free, cell-based, and animal-based experiments to define the pharmacokinetic profile of the food based phytochemical carnosol. Mice were administered carnosol (100 mg/kg body weight) by oral gavage and plasma levels were analyzed by LC-MS/MS to establish a detailed pharmacokinetic profile. The maximum plasma concentration exceeded 1 µM after a single administration. The results are significant as they offer insights on the potential for food-drug interactions between carnosol from rosemary and active pharmaceutical ingredients. Carnosol was observed to inhibit selected CYP450 enzymes and modulate metabolic enzymes and transporters in in vitro assays.

Cytochrome P450-Mediated Metabolic Characterization of a Mono-Carbonyl Curcumin Analog WZ35.

WZ35 is a monocarbonyl analog of curcumin, which had been proved advantage over curcumin in chemical stability and antitumor activity. However, its pharmacokinetic profile has not been determined. In the present study, an ultraperformance liquid chromatography-tandem mass spectrometry assay was developed to detect concentration of WZ35 in rat plasma. Subsequently, pharmacokinetic study showed that the oral bioavailability of WZ35 is 10.56%. Cytochrome P450 (CYP450) plays a major role in metabolizing exogenous substance. The concentration of WZ35 was sharply decreased while incubating with microsome. It's indicated that WZ35 is a substrate of CYP450s. Molecular docking assay showed that WZ35 can combine with CYP2B6 and CYP2C9 to form much more stable complex. The lowest docking energy was generated in complex with CYP2E1. The inhibition of CYP450s by WZ35 was also evaluated. Pan inhibitions of WZ35 on rat CYP3A2, CYP2B1, CYP2C11, CYP2D1, and -CYP2E1 were observed by detecting probe substrates (midazolam, bupropion, tolbutamide, dextromethorphan, chlorzoxazone) and metabolites accordingly. On an average, 80% activities of enzymes were blocked. Mechanistically, the inhibitions of WZ35 on CYP3A2, CYP2B1, CYP2E1 were in a time-dependent manner according to the results of IC50 shift assay. The collective data demonstrated that the oral bioavailability of monocarbonyl analog of curcumin has significantly improved compared to curcumin. It's both the substrate and inhibitor of CYP450s through in a time-dependent mechanism.

Application of Osmotic Pumps for Sustained Release of 1-Aminobenzotriazole and Inhibition of Cytochrome P450 Enzymes in Mice: Model Comparison with the Hepatic P450 Reductase Null Mouse.

The effectiveness of controlled release 1-aminobenzotriazole (ABT) administration to inhibit cytochrome P450 (P450) enzymes has been evaluated in mice. To maximize the duration of P450 inhibition in vivo, ABT was administered via an osmotic pump. The degree of P450 inhibition was compared with that achieved with a single bolus dose of ABT. Two-hour prior subcutaneous treatment of mice with ABT (50 mg/kg) inhibited antipyrine clearance by 88%. A less pronounced inhibitory effect (29% reduction in clearance) was observed when ABT was administered 24-hours before antipyrine administration, indicating partial restoration of P450 activity during this longer pretreatment time. The duration of ABT in mice was very short (mean residence time = 1.7 hours) after subcutaneous bolus administration. When the inhibitor was delivered by an osmotic pump, maximum blood concentrations of the inhibitor were observed 24 hours after device implantation and were maintained at steady state for 6 days. Inhibition of P450 activity, as measured by antipyrine clearance, was confirmed at 24 hours and 120 hours after pump implantation, highlighting the utility of this method as a longer-term model for P450 inhibition in mice. The magnitude of P450 inhibition in ABT-treated mice was compared with that in hepatic P450 reductase null mice and both models were comparable. In vivo ABT administration by an osmotic pump offers an effective approach for longer-term P450 inhibition in mice and avoids the necessity for multiple dosing of the inhibitor.

Use of Human Plasma Samples to Identify Circulating Drug Metabolites that Inhibit Cytochrome P450 Enzymes.

Drug interactions elicited through inhibition of cytochrome P450 (P450) enzymes are important in pharmacotherapy. Recently, greater attention has been focused on not only parent drugs inhibiting P450 enzymes but also on possible inhibition of these enzymes by circulating metabolites. In this report, an ex vivo method whereby the potential for circulating metabolites to be inhibitors of P450 enzymes is described. To test this method, seven drugs and their known plasma metabolites were added to control human plasma at concentrations previously reported to occur in humans after administration of the parent drug. A volume of plasma for each drug based on the known inhibitory potency and time-averaged concentration of the parent drug was extracted and fractionated by high-pressure liquid chromatography-mass spectrometry, and the fractions were tested for inhibition of six human P450 enzyme activities (CYP1A2, CYP2C8, CYP2C9, CYP2C19, CYP2D6, and CYP3A4). Observation of inhibition in fractions that correspond to the retention times of metabolites indicates that the metabolite has the potential to contribute to P450 inhibition in vivo. Using this approach, norfluoxetine, hydroxyitraconazole, desmethyldiltiazem, desacetyldiltiazem, desethylamiodarone, hydroxybupropion, erythro-dihydrobupropion, and threo-dihydrobupropion were identified as circulating metabolites that inhibit P450 activities at a similar or greater extent as the parent drug. A decision tree is presented outlining how this method can be used to determine when a deeper investigation of the P450 inhibition properties of a drug metabolite is warranted.

In vivo use of the CYP inhibitor 1-aminobenzotriazole to increase long-term exposure in mice.

1-Aminobenzotriazole (ABT) is a well-known in vivo nonspecific inhibitor of cytochrome P450 (CYP) enzymes. An effective dosing regimen of ABT for a multiple-administration study is needed to conduct pharmacological studies for proof-of-concept, although it has been established for single-administration study, to characterize the pharmacokinetics of drug candidates. This study demonstrated a suitable dosing vehicle of ABT for continuous administration and increased exposure to antipyrine, which is a nonspecific probe of CYP, using ABT for a long period in mice. The dosing vehicle of ABT was 0.5% (w/v) hydroxypropyl methylcellulose and 0.5% (v/v) Tween 80 in N,N-dimethylacetamide/20% hydroxypropyl-ß-cyclodextrin aqueous solution (2:8, v/v) based on the duration of apparent solubility. After implantation of an ALZET osmotic pump with ABT, the plasma concentrations of ABT were maintained at more than 4.1 µg/ml over 336 h. Compared with the vehicle group, the CLtot of antipyrine with ABT decreased to approximately one-fourth, and the BA of antipyrine with ABT increased up to 3-fold. In addition, the enhancement of exposure of antipyrine by ABT was maintained over the 336 h. The body weight, food consumption and hematological parameters of mice did not change with ABT administration for 16 days. These findings demonstrated that pretreatment of ABT can increase long-term exposure using continuous administration with the ALZET osmotic pump in mice with no overt toxicity. It is concluded that the in vivo use of 1-aminobenzotriazole can be applied to pharmacological studies for proof-of-concept, thus contributing to the selection of drug candidates at an early drug discovery stage. Copyright © 2016 John Wiley & Sons, Ltd.

In vitro and in vivo characterization of CYP inhibition by 1-aminobenzotriazole in rats.

1-Aminobenzotriazole (ABT) is a non-isoform specific, time-dependent inhibitor of cytochrome P450 (CYP) enzymes used extensively in preclinical studies to determine the relative contribution of oxidative metabolism. Although ABT has been widely used, the extent and duration of its inhibitory effect is not well understood. The purpose of this study is to characterize ABT inhibition of CYP in rats at both the hepatic and intestinal levels. In vivo studies using midazolam (p.o. and i.v.), as a probe for CYP activity, demonstrated that CYP inhibition was not complete even at the highest dose (300 mg/kg). Additional in vivo studies demonstrated that even at 26 h following ABT administration, there was significant CYP inhibition remaining. In vitro studies, conducted in both rat liver microsomes and rat hepatocytes, confirm that ABT is a time-dependent inhibitor of rat CYP orthologs. However, in rat liver microsomes, there was more than 15% CYP activity remaining following a 60 min preincubation at 2 mm ABT and 5-10% of CYP activity was remaining in rat hepatocytes suspended in rat plasma following a 60 min preincubation at 2 mm ABT. 1-Aminobenzotriazole is a useful tool in elucidating the oxidative component of metabolism in preclinical species; however, conclusions made from the preclinical use of ABT should not operate under the assumption that CYP enzymatic activity is completely inhibited. Copyright © 2016 John Wiley & Sons, Ltd.

Evaluating bioanalytical capabilities of paper spray ionization for abiraterone drug quantification in patient plasma.

Paper spray ionization (PSI) is a direct, fast, and low-cost ambient ionization technique which may have clinical utility for qualitative and quantitative analysis of therapeutic drugs and metabolites from patient specimens. We developed and validated a PSI-mass spectrometry (PSI-MS/MS) method according to the US-FDA guidelines for bioanalytical studies to measure the prostate cancer drug abiraterone directly from patient plasma. The established linearity range was 3.1-156.8 ng/mL with a precision (%CV) and an accuracy (%) range of 0.5-10.7 and 93.5-103.2, respectively. The mean internal standard normalized matrix factor for abiraterone was just below 1 with highest %CV of 10.2 at the low-level quality control. In benchmarking the performance of this assay against a published LC-MS/MS assay, we showed they were mostly equivalent, with the exception of accuracy with clinical samples. We found the quantitative values observed for abiraterone measured directly from patient plasma using PSI-MS/MS showed positive bias. Upon investigation, we concluded the increased values were due to summed quantitation of isomeric abiraterone conjugates and metabolites which are separable by LC-MS/MS, but not with the current PSI-MS/MS configuration. Despite demonstrating the utility of PSI-MS/MS for rapid bioanalysis, this study also highlighted a limitation encountered with the direct analysis of abiraterone in clinical samples.

Inhibitory effects of type 2 diabetes serum components in P450 inhibition assays can potential diagnose asymptomatic diabetic mice.

Human cytochrome P450 (or CYP) inhibition rates were investigated in sera from high fat diet (HFD)-induced type 2 diabetes (T2D), T2D recovered, and asymptomatic mice models to verify whether P450 inhibition assays could be used for the detection of disease, evaluation of therapeutic effect, and early diagnosis of T2D. In T2D mice, the blood glucose levels markedly increased; while blood glucose levels of recovered mice exceeded 200 mg dL-1, these eventually returned to the levels seen in control mice. In asymptomatic mice fed with short term HFD (stHFD), no changes in blood glucose levels were observed. The inhibition rates of CYP1A2, CYP2A13, and CYP2C18 in T2D mice significantly increased. Whereas in recovered mice, these changes returned to the same levels noted in the control mice. Changes in the inhibition rates of CYP2A13 and CYP2C18 in stHFD mice were similar to those in T2D mice. A receiver operating characteristic (ROC) curve analysis showed high area under the ROC curve (AUC) values (0.879-1.000) of CYP2A13 and CYP2C18 in T2D and stHFD mice, indicating their high diagnostic accuracy. Collectively, this study validates the P450 inhibition assay as a method for the therapeutic evaluation and early diagnosis of T2D mouse models.

In Vitro and In Vivo Correlation of Hepatic Fraction of Metabolism by P450 in Dogs.

1-Aminobenzotriazole (ABT) has been widely used as a nonspecific mechanism-based inhibitor of cytochrome P450 (P450) enzymes. It is extensively used in preclinical studies to determine the relative contribution of oxidative metabolism mediated by P450 in vitro and in vivo. The aim of present study was to understand the translation of fraction metabolized by P450 in dog hepatocytes to in vivo using ABT, for canagliflozin, known to be cleared by P450-mediated oxidation and UDP-glucuronosyltransferases-mediated glucuronidation, and 3 drug discovery project compounds mainly cleared by hepatic metabolism. In a dog hepatocyte, intrinsic clearance assay with and without preincubation of ABT, 3 Lilly compounds exhibited a wide range of fraction metabolized by P450. Subsequent metabolite profiling in dog hepatocytes demonstrated a combination of metabolism by P450 and UDP-glucuronosyltransferases. In vivo, dogs were pretreated with 50 mg/kg ABT or vehicle at 2 h before intravenous administration of canagliflozin and Lilly compounds. The areas under the concentration-time curve (AUC) were compared for the ABT-pretreated and vehicle-pretreated groups. The measured AUCABT/AUCveh ratios were correlated to fraction of metabolism by P450 in dog hepatocytes, suggesting that in vitro ABT inhibition in hepatocytes is useful to rank order compounds for in vivo fraction of metabolism assessment.

Food effects on abiraterone pharmacokinetics in healthy subjects and patients with metastatic castration-resistant prostate cancer.

Food effect on abiraterone pharmacokinetics and safety on abiraterone acetate coadministration with low-fat or high-fat meals was examined in healthy subjects and metastatic castration-resistant prostate cancer (mCRPC) patients. Healthy subjects (n = 36) were randomized to abiraterone acetate (single dose, 1000 mg) + low-fat meal, + high-fat meal, and fasted state. mCRPC patients received repeated doses (abiraterone acetate 1000 mg + 5 mg prednisone twice daily; days 1-7) in a modified fasting state followed by abiraterone acetate plus prednisone within 0.5 hours post-low-fat (n = 6) or high-fat meal (n = 18; days 8-14). In healthy subjects, geometric mean (GM) abiraterone area under plasma concentration-time curve (AUC) increased ∼5- and ∼10-fold, respectively, with low-fat and high-fat meals versus fasted state (GM [coefficient of variation], 1942 [48] and 4077 [37] ng · h/mL vs 421 [67] ng · h/mL, respectively). In mCRPC patients, abiraterone AUC was ∼2-fold higher with a high-fat meal and similar with a low-fat meal versus modified fasting state (GM [coefficient of variation]: 1992 [34] vs 973 [58] ng · h/mL and 1264 [65] vs 1185 [90] ng · h/mL, respectively). Adverse events (all grade ≤ 3) were similar, with high-fat/low-fat meals or fasted/modified fasting state. Short-term dosing with food did not alter abiraterone acetate safety.

Pharmacokinetics of abiraterone in healthy Japanese men: dose-proportionality and effect of food timing.

PURPOSE: Abiraterone acetate (AA) was recently approved for castration-resistant prostate cancer in Japan. Two phase 1 studies were conducted to assess the pharmacokinetics of abiraterone after single-dose administration in Japanese healthy men and to evaluate the effects of food timing on abiraterone pharmacokinetics after single-dose administration of AA in Japanese and Caucasian healthy men. METHODS: In the dose-proportionality study, subjects (n = 30 Japanese) were randomly assigned to receive single doses of 250, 500, and 1,000 mg AA, and in the food-timing study, subjects (n = 22 Japanese and n = 23 Caucasian) randomly received single doses of 1,000 mg AA under fasted (overnight) and three different modified fasting conditions. RESULTS: Mean C(max) and AUC(∞) for abiraterone increased dose-dependently in Japanese healthy men; however, 90 % confidential interval (CI) was outside the predefined dose-proportionality criteria. Based on geometric mean ratios and 90 % CIs (versus overnight fasting condition), abiraterone exposure (AUC) increased significantly with dosing 1 h premeal, 2 h postmeal, or in between two meals 4 h apart by 57 %, 595 %, and 649 %, respectively. CONCLUSION: No clinically meaningful difference was observed in the pharmacokinetics of abiraterone between Caucasian and Japanese subjects.

Impact of inhalational exposure to ethanol fuel on the pharmacokinetics of verapamil, ibuprofen and fluoxetine as in vivo probe drugs for CYP3A, CYP2C and CYP2D in rats.

Occupational toxicology and clinical pharmacology integration will be useful to understand potential exposure-drug interaction and to shape risk assessment strategies in order to improve occupational health. The aim of the present study was to evaluate the effect of exposure to ethanol fuel on in vivo activities of cytochrome P450 (CYP) isoenzymes CYP3A, CYP2C and CYP2D by the oral administration of the probe drugs verapamil, ibuprofen and fluoxetine. Male Wistar rats exposed to filtered air or to 2000 ppm ethanol in a nose-only inhalation chamber during (6 h/day, 5 days/week, 6 weeks) received single oral doses of 10 mg/kg verapamil or 25 mg/kg ibuprofen or 10 mg/kg fluoxetine. The enantiomers of verapamil, norverapamil, ibuprofen and fluoxetine in plasma were analyzed by LC-MS/MS. The area under the curve plasma concentration versus time extrapolated to infinity (AUC(0-∞)) was calculated using the Gauss-Laguerre quadrature. Inhalation exposure to ethanol reduces the AUC of both verapamil (approximately 2.7 fold) and norverapamil enantiomers (>2.5 fold), reduces the AUC(0-∞) of (+)-(S)-IBU (approximately 2 fold) and inhibits preferentially the metabolism of (-)-(R)-FLU. In conclusion, inhalation exposure of ethanol at a concentration of 2 TLV-STEL (6 h/day for 6 weeks) induces CYP3A and CYP2C but inhibits CYP2D in rats.

A semi-automated LC-MS/MS method for the determination of LCI699, a steroid 11ß-hydroxylase inhibitor, in human plasma.

A novel liquid chromatographic method with tandem mass spectrometric detection (LC-MS/MS) for the determination of LCI699 was developed and validated with dynamic ranges of 0.0500-50.0 ng/mL and 1.00-1,000 ng/mL using 0.0500 mL and 0.100mL, respectively, of human plasma. LCI699 and the internal standard, [M+6]LCI699, were extracted from fortified human plasma via protein precipitation. After transfer or dilution of the supernatant followed by solvent evaporation and/or reconstitution, the extract was injected onto the LC-MS/MS system. Optimal chromatographic separation was achieved on an ACE C18 (50 mm × 4.6mm, 3 µm) column with 30% aqueous methanol (containing 0.5% acetic acid and 0.05% TFA) as the mobile phase run in isocratic at a flow rate of 1.0 mL/min. The total analysis cycle time is approximately 3.5 min per injection. The addition of an ion-pair reagent, TFA (0.05%, v/v), to the mobile phases significantly improved the chromatographic retention and resolution of the analyte on silica based reversed-phase column. Although addition of TFA to the mobile phase suppresses the ESI signals of the analyte due to its ion-pairing characteristics in the gas phase of MS source, this negative impact was effectively alleviated by adding 0.5% acetic acid to the mobile phase. The current method was validated for sensitivity, selectivity, linearity, reproducibility, stability and recovery. For the low curve range (0.0500-50.0 ng/mL), the accuracy and precision for the LLOQs (0.0500 ng/mL) were -13.0 to 2.0% bias and 3.4-19.2% CV, respectively. For other QC samples (0.100, 6.00, 20.0 and 40.0 ng/mL), the precision ranged from 1.2 to 9.0% and from 3.8 to 8.8% CV, respectively, in the intra-day and inter-day evaluations. The accuracy ranged from -11.3 to 8.0% and -7.2 to 1.6% bias, respectively, in the intra-day and inter-day batches. For the high curve range (1.00-1,000 ng/mL), the accuracy and precision for the LLOQs (1.00 ng/mL) were 1.0-15.0% bias and 7.4-9.2% CV, respectively. For the other QC samples (3.00, 20.0, 200 and 750 ng/mL), the precision ranged from 0.8 to 7.0% and from 1.9 to 5.2% CV, respectively, in the intra-day and inter-day evaluations. The accuracy ranged from -2.5 to 4.0% and 0.7-1.0% bias, respectively, in the intra-day and inter-day batches. Additional assessments of incurred sample stability (ISS) and incurred sample reanalysis (ISR) were conducted to demonstrate the ruggedness and robustness of the assay method. The absence of adverse matrix effect and carryover was also demonstrated. The validated method was successfully used to support rapid turnaround human pharmacokinetic studies.

Potent 11ß-hydroxylase inhibitors with inverse metabolic stability in human plasma and hepatic S9 fractions to promote wound healing.

Topical application of CYP11B1 inhibitors to reduce cutaneous cortisol is a novel strategy to promote healing of chronic wounds. Pyridyl substituted arylsulfonyltetrahydroquinolines were designed and synthesized resulting in a strong inhibitor 34 (IC50 = 5 nM). It showed no inhibition of CYP17 and CYP19 and no mutagenic effects. It exhibited inverse metabolic stability in plasma (t1/2 ≫ 150 min), which is similar to wound fluid in composition, and in liver S9 fractions (t1/2 = 16 min).

A proposed screening paradigm for discovery of covalent inhibitor drugs.

The in vitro and in vivo preclinical ADME properties of 10 clinically late stage or marketed covalent inhibitors were evaluated in order to define advancement criteria for discovery of future drugs in this arena. Our studies revealed the following: After incubating with S9 fractions for 30 minutes, the rat and human in vitro stability for these compounds ranged from 1% to 100%. The blood stability ranged from 30% to 100%. There was a broad range of CYP inhibition with prevalence for time-dependent inhibition of at least one enzyme. The Caco-2 permeability (A→B) ranged from negligible (0.6 x 10(-6) cm/s) to highly permeable (31 x 10(-6) cm/s) and the efflux ratio also varied widely (0.2-30). Most of the compounds were highly protein bound in both rat and human with binding ≥ 90%. Rat plasma clearance for the 10 compounds ranged from slow (11 mL/min/kg) to very rapid (350 mL/min/kg). The Vss ranged from low (0.67 L/kg) to very high (115 L/kg). MRT's also ranged from short (0.5 hr) to long (7.4 hr). The oral exposures also showed a very broad range with CMax's ranging from 0.01-77 µM and exposure levels ranging from 0.03-106 µM.hr. In conclusion, the wide range in in vitro and in vivo ADME data makes these particular ADME assays non-discriminatory in the selection of promising compounds. In our opinion, non-traditional assays such as target mass modification, target confirmation by amino acid sequencing, cellular target occupancy, and target turnover rate data in combination with the pharmacokinetic profiles are the critical considerations for progression of irreversible compounds in early discovery.

Single-dose pharmacokinetic studies of abiraterone acetate in men with hepatic or renal impairment.

Three open-label, single-dose studies investigated the impact of hepatic or renal impairment on abiraterone acetate pharmacokinetics and safety/tolerability in non-cancer patients. Patients (n = 8 each group) with mild/moderate hepatic impairment or end-stage renal disease (ESRD), and age-, BMI-matched healthy controls received a single oral 1,000 mg abiraterone acetate (tablet dose); while patients (n = 8 each) with severe hepatic impairment and matched healthy controls received 125- and 2,000-mg abiraterone acetate (suspension doses), respectively (systemic exposure of abiraterone acetate suspension is approximately half to that of tablet formulation). Blood was sampled at specified timepoints up to 72 or 96 hours postdose to measure plasma abiraterone concentrations. Abiraterone exposure was comparable between healthy controls and patients with mild hepatic impairment or ESRD, but increased by 4-fold in patients with moderate hepatic impairment. Despite a 16-fold reduction in dose, abiraterone exposure in patients with severe hepatic impairment was about 22% and 44% of the Cmax and AUC∞ of healthy controls, respectively. These results suggest that abiraterone pharmacokinetics were not changed markedly in patients with ESRD or mild hepatic impairment. However, the capacity to eliminate abiraterone was substantially compromised in patients with moderate or severe hepatic impairment. A single-dose administration of abiraterone acetate was well-tolerated.