The inhibition of CYP1A2, CYP2C9, and CYP2D6 by pterostilbene in human liver microsomes.

This study used human liver microsomes to assess pterostilbene's effect on the metabolic activity of cytochrome P450 (CYP) 1A2, CYP2C9, and CYP2D6. The metabolism of their substrates (phenacetin, tolbutamide, and dextromethorphan) was assayed by quantifying their relevant metabolites by HPLC. The IC50 value was used to express the strength of inhibition, and the value of a volume per dose index (VDI) was used to indicate the metabolic ability of the enzyme. In this study, pterostilbene inhibited CYP1A2, CYP2C9, and CYP2D6's metabolic activities in vitro. CYP2C9's activity was most significantly inhibited by pterostilbene; its IC50 value was 0.12±0.04 µM. The IC50 value of CYP1A2 and CYP2D6 was 56.3±10.4 µM and 62.33±11.4 µM, respectively. The finding that suggests that pterostilbene has the potential to interact with CYP2C9 substrates in vivo. These results warrant clinical studies to assess the in vivo significance of these interactions.

Single-Dose Pharmacokinetics, Safety, and Tolerability of Avadomide (CC-122) in Subjects With Mild, Moderate, or Severe Renal Impairment.

CC-122 (Avadomide) is a nonphthalimide analogue of thalidomide that has multiple pharmacological activities including immune modulation of several immune cell subsets, antigrowth activity, antiproliferative activity, and antiangiogenic activity. CC-122 as monotherapy and in combination with other agents is being evaluated for multiple indications including hematologic malignancies and advanced solid tumors. Given that renal clearance is one of the major routes of elimination for CC-122 and its clearance/exposure could be affected by renal impairment, a total of 50 subjects with various degrees of renal function were enrolled in an open-label, single-dose study to evaluate the impact of renal impairment on CC-122 pharmacokinetic disposition. The study showed that following administration of a single oral dose of 3 mg CC-122, renal impairment reduced both the apparent total plasma clearance and renal clearance of CC-122, but it had less impact on CC-122 absorption, as demonstrated by similar Tmax and Cmax among groups with various degrees of renal function. Compared with exposure in subjects with normal renal function, total plasma exposure to CC-122 increased by ∼20%, ∼50%, and ∼120% in subjects with mild, moderate, and severe renal insufficiency, respectively. Results from this study combined with modeling/simulation suggest that dose adjustments are necessary in patients with moderate or severe but not with mild renal impairment. Finally, a single dose of 3 mg CC-122 was safe and well tolerated by healthy subjects and subjects with mild, moderate, and severe renal impairment.

Dose-Related Modulatory Effects of Polymeric Black Tea Polyphenols (PBPs) on Initiation and Promotion Events in B(a)P and NNK-Induced Lung Carcinogenesis.

Our understanding of dose-related effects of polymeric black tea polyphenols (PBPs), the most abundant polyphenols in black tea, is limited. In the present study, the effect of various doses of black tea (0.75, 1.5, and 3%)-derived PBP-rich extract on biochemical parameters and lung carcinogenicity in A/J mice was investigated. Pretreatment with PBPs showed the dose-related decrease in B(a)P-induced expression and activity of CYP1A1 in the liver while CYP1A2 expression and activity in the lung. Dose-dependent significant increase in PBP-mediated over-expression and activity of GSTs (alpha in the liver while pi in the lung) were observed in polyphenol-treated groups. Significant dose-related decrease in number and intensity of BPDE-DNA adducts were observed in liver and lung. Black tea (1.5%, 3%)-derived PBPs showed dose-mediated decrease in lung tumor incidence and multiplicity which was further correlated with different molecular markers like cell proliferation and apoptosis in B(a)P and NNK model. In conclusion, dose-dependent chemopreventive effects of PBPs, both anti-initiating (induction of phase II and inhibition of carcinogen-induced phase-I enzymes leading to decrease in BPDE-DNA adducts) and anti-promoting (decreased cell proliferation and increased apoptosis lowering incidence and/or multiplicity of lung lesions), were observed in A/J mice without significant toxicity.

Acute Decompensated Heart Failure After Initiation of Amiodarone in a Patient With Anderson-Fabry Disease.

A 54-year-old man with the lysosomal storage disorder Anderson-Fabry disease (AFD) and cardiac involvement was placed on amiodarone for treatment of symptomatic paroxysmal atrial fibrillation. Shortly thereafter, he developed symptoms of acute decompensated heart failure, requiring hospital admission. Endomyocardial biopsy demonstrated findings consistent with AFD and possible amiodarone toxicity. Amiodarone was discontinued, and the patient's heart failure resolved with return to baseline status. Amiodarone is known to alter lysosomal pH and enzyme activity, and this case illustrates how it should be used with considerable caution in patients with AFD.

Co-Prescription of Strong CYP1A2 Inhibitors and the Risk of Tizanidine-Associated Hypotension: A Retrospective Cohort Study.

Tizanidine, a widely used muscle relaxant that can lower blood pressure, is metabolized by the cytochrome P450 1A2 (CYP1A2). We studied 1,626 patients prescribed tizanidine and 5,012 prescribed cyclobenzaprine concurrently with a strong CYP1A2 inhibitor. The primary outcome was severe hypotension, defined as systolic blood pressure (SBP) ≤ 70 mmHg during periods of drug co-exposure. Severe hypotension occurred more often in the tizanidine group (2.03%; n = 33) than the cyclobenzaprine group (1.28%; n = 64); odds ratio (OR) = 1.60; P = 0.029. This difference remained statistically significant after adjustment for a log-transformed propensity score that included age, sex, race, Charlson's comorbidity index, and concurrent use of antihypertensive medications (OR = 1.57; P = 0.049). A sensitivity analysis that defined hypotension as SBP < 90 mmHg also yielded higher rates of hypotension among patients prescribed tizanidine. In conclusion, CYP1A2 inhibition increases the risk of hypotensive episodes associated with the use of tizanidine in routine clinical practice.

In Vivo Assessment of the Effect of CYP1A2 Inhibition and Induction on Pomalidomide Pharmacokinetics in Healthy Subjects.

Pomalidomide is an immunomodulatory drug, and the dosage of 4 mg per day taken orally on days 1-21 of repeated 28-day cycles has been approved in the European Union and the United States to treat patients with relapsed/refractory multiple myeloma. In vitro data showed that pomalidomide is a substrate of multiple cytochrome P450 (CYP) isozymes and that its oxidative metabolism is mediated primarily by CYP1A2 and CYP3A4, with minor contributions from CYP2C19 and CYP2D6. The effect of CYP1A2 inhibition by fluvoxamine (a strong CYP1A2 inhibitor) and CYP1A2 induction by smoking on pomalidomide pharmacokinetics in healthy subjects has been assessed in 2 separate phase 1 open-label, single-dose studies. Following administration of a single oral dose of 4 mg pomalidomide, the plasma exposure when coadministered with fluvoxamine was 225.1% and 123.7% of that when administered alone for the total plasma exposure (AUC0-inf ) and the plasma peak exposure (Cmax ), respectively. In smokers with elevated CYP1A2 activity demonstrated by high caffeine clearance (a marker of CYP1A2 induction), the AUC0-inf was 32.3% lower, whereas the Cmax was 14.4% higher than that in nonsmokers. In addition, pomalidomide was safe and well tolerated as a single oral dose of 4 mg in healthy male smokers and nonsmokers ≥ 40 to ≤ 80 years old, and a single oral dose of 4 mg pomalidomide coadministered with multiple oral 50-mg doses of the CYP1A2 inhibitor fluvoxamine compared with pomalidomide alone was safe and well tolerated by the healthy male subjects.

Drinking Ethanol Has Few Acute Effects on CYP2C9, CYP2C19, NAT2, and P-Glycoprotein Activities but Somewhat Inhibits CYP1A2, CYP2D6, and Intestinal CYP3A: So What?

We quantified the effect of acute ethanol exposure (initial blood concentrations 0.7 g/L) on major drug metabolizing enzymes and p-glycoprotein. Sixteen healthy Caucasians participated in a randomized crossover study with repeated administration of either vodka or water. Enzyme/transporter activity was assessed by a cocktail of probe substrates, including caffeine (CYP1A2/NAT2), tolbutamide (CYP2C9), omeprazole (CYP2C19), dextromethorphan (CYP2D6), midazolam (CYP3A), and digoxin (P-glycoprotein). The ratio of AUC0-t of dextromethorphan for ethanol/water coadministration was 1.95 (90% confidence interval (CI) 1.48-2.58). The effect was strongest in individuals with a CYP2D6 genotype predicting high activity (n = 7, ratio 2.66, 90% CI 1.65-4.27). Ethanol increased caffeine AUC0-t 1.38-fold (90% CI 1.25-1.52) and reduced intestinal midazolam extraction 0.77-fold (90% CI 0.69-0.86). The other probe drugs were not affected by ethanol. The results suggest that acute ethanol intake typically has no clinically important effect on the enzymes/transporters tested.

A drug-drug interaction study to assess the effect of the CYP1A2 inhibitor fluvoxamine on the pharmacokinetics of dovitinib (TKI258) in patients with advanced solid tumors.

PURPOSE: Dovitinib is an orally available multi tyrosine kinase inhibitor which inhibits VEGFR 1-3, FGFR 1-3, and PDGFR. This study was performed to investigate the potential drug-drug interaction of dovitinib with the CYP1A2 inhibitor fluvoxamine in patients with advanced solid tumors. METHODS: Non-smoking patients of ≥ 18 years with advanced solid tumors, excluding breast cancer, were included. Patients were treated with a dose of 300 mg in 5 days on/2 days off schedule. Steady-state pharmacokinetic assessments of dovitinib were performed with or without fluvoxamine. RESULTS: Forty-five patients were enrolled; 24 were evaluable for drug-drug interaction assessment. Median age was 60 years (range 30-85). At steady state the geometric mean for dovitinib (coefficient of variation%) of the area under the plasma concentration-time curve (AUC0-72h) and maximum concentration (C max) were 2880 ng/mL h (47%) and 144 ng/mL (41%), respectively. Following administration of dovitinib in combination with fluvoxamine the geometric mean of dovitinib AUC0-72h and C max were 8290 ng/mL h (60%) and 259 ng/mL (45%), respectively. The estimated geometric mean ratios for dovitinib AUC0-72h and C max (dovitinib + fluvoxamine vs. dovitinib alone) were 2.88 [90% confidence interval (CI) 2.58, 3.20] and 1.80 (90% CI 1.66, 1.95). This effect is considered a moderate drug-drug interaction. CONCLUSIONS: Fluvoxamine co-administration resulted in a 80% increase in C max and a 188% increase in AUC0-72h of dovitinib. Given the increase in exposure to dovitinib observed, patients are at risk of dovitinib related toxicity. Dovitinib should, therefore, not be co-administered with moderate and strong CYP1A2 inhibitors, without dose reduction.

In vitro metabolism of 4, 5-dimethoxycanthin-6-one by human liver microsomes and its inhibition on human CYP1A2.

AIMS: P. quassioides is a traditional Chinese medicine used for the treatment of gastroenteritis, snakebite, infection and hypertension in China. 4, 5-dimethoxycanthin-6-one is one of the main active canthinone alkaloid isolated from P. quassioides. The aim of this work was to identify the cytochrome P (CYP) 450 enzymes responsible for the metabolism of 4, 5-dimethoxycanthin-6-one (DCO) and to evaluate the inhibitory effect of DCO on CYP activity in human liver microsomes (HLM) in vitro. MATERIALS AND METHODS: the CYP isoforms responsible for DCO metabolism and the inhibitory effects of DCO on CYP activity was studied in HLM. KEY FINDINGS: The in vitro metabolic enzyme of DCO was CYP3A4 (mediated the formation of metabolites M1-M5), CYP2C9 (mediated the formation of metabolites M1-M3, M6 and M8) and CYP2D6 (mediated the formation of metabolite M3) in HLM. Furthermore, the present work found that DCO uncompetitively inhibited CYP1A2-mediated phenacetin O-deethylation with an IC50 value of 1.7µM and a Ki value of 2.6µM. SIGNIFICANCE: The results suggested that the metabolic interaction should be existed when the substrate drugs of CYP1A2 were co-administered with DCO or traditional Chinese medicine containing it, such as the extract of P. quassioides and Kumu injection.

Scaffold Hopping and Optimization of Maleimide Based Porcupine Inhibitors.

Porcupine is an O-acyltransferase that regulates Wnt secretion. Inhibiting porcupine may block the Wnt pathway which is often dysregulated in various cancers. Consequently porcupine inhibitors are thought to be promising oncology therapeutics. A high throughput screen against porcupine revealed several potent hits that were confirmed to be Wnt pathway inhibitors in secondary assays. We developed a pharmacophore model and used the putative bioactive conformation of a xanthine inhibitor for scaffold hopping. The resulting maleimide scaffold was optimized to subnanomolar potency while retaining good physical druglike properties. A preclinical development candidate was selected for which extensive in vitro and in vivo profiling is reported.

Discovery and Optimization of Chromeno[2,3-c]pyrrol-9(2H)-ones as Novel Selective and Orally Bioavailable Phosphodiesterase 5 Inhibitors for the Treatment of Pulmonary Arterial Hypertension.

Phosphodiesterase 5 (PDE5) inhibitors have been used as clinical agents to treat erectile dysfunction and pulmonary arterial hypertension (PAH). Herein, we detail the discovery of a novel series of chromeno[2,3-c]pyrrol-9(2H)-one derivatives as selective and orally bioavailable inhibitors against phosphodiesterase 5. Medicinal chemistry optimization resulted in 2, which exhibits a desirable inhibitory potency of 5.6 nM with remarkable selectivity as well as excellent pharmacokinetic properties and an oral bioavailability of 63.4%. In addition, oral administration of 2 at a dose of 5.0 mg/kg caused better pharmacodynamics effects on both mPAP (mean pulmonary artery pressure) and RVHI (index of right ventricle hypertrophy) than sildenafil citrate at a dose of 10.0 mg/kg. These activities along with its reasonable druglike properties, such as human liver microsomal stability, cytochrome inhibition, hERG inhibition, and pharmacological safety, indicate that 2 is a potential candidate for the treatment of PAH.

Inhibition of Procarcinogen Activating Enzyme CYP1A2 Activity and Free Radical Formation by Caffeic Acid and its Amide Analogues.

OBJECTIVES: Caffeic acid (CAF) and its amide analogues, ethyl 1-(3',4'-dihydroxyphenyl) propen amide (EDPA), phenethyl 1-(3',4'-dihydroxyphenyl) propen amide (PEDPA), phenmethyl 1- (3',4'-dihydroxyphenyl) propen amide (PMDPA) and octyl 1-(3',4'-dihydroxyphenyl) propen amide (ODPA) were investigated for the inhibition of procarcinogen activating enzyme. METHODS: CYP1A2 and scavenging activity on formation of nitric oxide, superoxide anion, DPPH radical and hydroxyl radical. RESULTS: It was found that they inhibited CYP1A2 enzyme by uncompetitive inhibition. Apparent Ki values of CAF, EDPA, PEDPA, PMDPA and ODPA were 0.59, 0.39, 0.45, 0.75 and 0.80 µM, respectively suggesting potent inhibitors of CYP1A2. Moreover, they potentially scavenged nitric oxide radical with IC 50 values of 0.12, 0.22, 0.28, 0.22 and 0.51 mM, respectively. The IC50 values of superoxide anion scavenging were 0.20, 0.22, 0.44, 2.18 and 2.50 mM, respectively. 1, 1- diphenyl-2- picrylhydrazyl (DPPH) radical-scavenging ability, shown as IC50 values, were 0.41, 0.29, 0.30, 0.89 and 0.84 mM, respectively. Moreover, the hydroxyl radical scavenging in vitro model was shown as IC50 values of 23.22, 21.06, 17.10, 17.21 and 15.81 µM, respectively. CONCLUSION: From our results, caffeic acid and its amide analogues are in vitro inhibitors of human CYP1A2 catalytic activity and free radical formation. They may be useful to be developed as potential chemopreventive agents that block CYP1A2-mediated chemical carcinogenesis.

Effects of suberoylanilide hydroxamic acid on rat cytochrome P450 enzyme activities.

Vorinostat (suberoylanilide hydroxamic acid, SAHA) is the first approved histone deacetylase (HDAC) inhibitor for the treatment of cutaneous T-cell lymphoma after progressive disease following two systemic therapies. The rats were randomly divided into SAHA groups (low, medium and high dosage) and control group. The SAHA group rats were given 12.3, 24.5, and 49 mg/kg SAHA, respectively, by continuous intragastric administration for 7 days. The influence of SAHA on the activities of CYP450 isoforms CYP2B6, CYP1A2, CYP2C19, CYP2D6 and CYP2C9 were evaluated by cocktail method, they were responsed by the changes of pharmacokinetic parameters of bupropion, phenacetin, tolbutamide, metroprolol and omeprazole. The five probe drugs were given to rats through intragastric administration, and the plasma concentration were determined by UPLC-MS/MS. The result of SAHA group compared to control group, there were statistical pharmacokinetics difference for bupropion, phenacetin, tolbutamide and metroprolol. Continuous intragastric administration for 7 days may induce the activities of CYP2C19 of rats, inhibit CYP1A2 and slightly inhibit CYP2B6 and CYP2D6 of rats. This may give advising for reasonable drug use after co-used with SAHA. The results indicated that drug co-administrated with SAHA may need dose adjustment. Furthermore, continuous intragastric administration of SAHA for 7 days, liver cell damaged, causing liver cell edema, in liver metabolism process.

Clinical assessment of drug-drug interactions of tasimelteon, a novel dual melatonin receptor agonist.

Tasimelteon ([1R-trans]-N-[(2-[2,3-dihydro-4-benzofuranyl] cyclopropyl) methyl] propanamide), a novel dual melatonin receptor agonist that demonstrates specificity and high affinity for melatonin receptor types 1 and 2 (MT1 and MT2 receptors), is the first treatment approved by the US Food and Drug Administration for Non-24-Hour Sleep-Wake Disorder. Tasimelteon is rapidly absorbed, with a mean absolute bioavailability of approximately 38%, and is extensively metabolized primarily by oxidation at multiple sites, mainly by cytochrome P450 (CYP) 1A2 and CYP3A4/5, as initially demonstrated by in vitro studies and confirmed by the results of clinical drug-drug interactions presented here. The effects of strong inhibitors and moderate or strong inducers of CYP1A2 and CYP3A4/5 on the pharmacokinetics of tasimelteon were evaluated in humans. Coadministration with fluvoxamine resulted in an approximately 6.5-fold increase in tasimelteon's area under the curve (AUC), whereas cigarette smoking decreased tasimelteon's exposure by approximately 40%. Coadministration with ketoconazole resulted in an approximately 54% increase in tasimelteon's AUC, whereas rifampin pretreatment resulted in a decrease in tasimelteon's exposure of approximately 89%.

Use of three-compartment physiologically based pharmacokinetic modeling to predict hepatic blood levels of fluvoxamine relevant for drug-drug interactions.

Using a three-compartment physiologically based pharmacokinetic (PBPK) model and a tube model for hepatic extraction kinetics, equations for calculating blood drug levels (Cb s) and hepatic blood drug levels (Chb s, proportional to actual hepatic drug levels), were derived mathematically. Assuming the actual values for total body clearance (CLtot ), oral bioavailability (F), and steady-state distribution volume (Vdss ), Cb s, and Chb s after intravenous and oral administration of fluvoxamine (strong perpetrator in drug-drug interactions, DDIs), propranolol, imipramine, and tacrine were simulated. Values for Cb s corresponded to the actual values for all tested drugs, and mean Chb and maximal Chb -to-maximal Cb ratio predicted for oral fluvoxamine administration (50 mg twice-a-day administration) were nearly 100 nM and 2.3, respectively, which would be useful for the predictions of the DDIs caused by fluvoxamine. Fluvoxamine and tacrine are known to exhibit relatively large F values despite having CLtot similar to or larger than hepatic blood flow, which may be because of the high liver uptake (almost 0.6) upon intravenous administration. The present method is thus considered to be more predictive of the Chb for perpetrators of DDIs than other methods.