Screening CYP3A single nucleotide polymorphisms in a Han Chinese population with a genotyping chip

Effect of recombinant CYP3A4 variants and interaction on imatinib metabolism in vitro

The aim of this study was to investigate the catalytic activity of 26 Cytochrome P450 3A4 (CYP3A4) variants and drug interactions on imatinib metabolism in recombinant insect microsomes. This study was designed with an appropriate incubation system and carried out in the constant temperature water. By using ultra-performance liquid chromatography tandem mass spectrometry (UPLC-MS/MS) to measure the quantities of its metabolite N-desmethyl imatinib, to elucidate the impacts of the CYP3A4 genetic polymorphism and drug interactions on the metabolism of imatinib. Consequently, as compared to CYP3A4.1, the intrinsic clearance (CLint) values of the variations were dramatically changed, rising from 2.34 % to 120.57 %. CYP3A4.14 showed an increase in CLint in comparison to CYP3A4.1, and the remaining 24 variants demonstrated decreases in catalytic activity for the metabolism of imatinib. In addition, the metabolism of imatinib was decreased to varied degrees by ketoconazole, itraconazole, and fluconazole in CYP3A4.1 and CYP3A4.18. Moreover, most of CYP3A4 variants showed similar trend of enzyme activity under different substrates of imatinib and cabozantinib, except 6 variants (CYP3A4.3,.4,.10,.15,.29 and.31). The first study of the effects of 26 CYP3A4 variants on imatinib metabolism will contribute to the clinical evaluation of imatinib and help personalize therapy in clinical settings.

Functional evaluation of vandetanib metabolism by CYP3A4 variants and potential drug interactions in vitro

AIM

To investigate the enzymatic properties of cytochrome P450 3A4 (CYP3A4) variants and their ability to metabolize vandetanib (VNT) in vitro, and to study potential drug interactions in combination with VNT.

METHOD

Recombinant CYP3A4 cell microsomes were prepared using a Bac-to-Bac baculovirus expression system. Enzymatic reactions were carried out, and the metabolites were determined by ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS).

RESULTS

The activities of 27 CYP3A4 variants were determined to assess the degree of VNT metabolism that occurred. Analysis indicated that there was enhanced intrinsic clearance (V_max/K_m, CLint) for eight variants (CYP3A4.2, 3, 9, 15, 16, 29, 32, and 33), while there was a significant decrease in CYP3A4.5, 7, 8, 10-14, 17-20, 23, 24, 28, 31, and 34. Compared with CYP3A4.1, no significant differences were found for CYP3A4.6 and 30. Furthermore, the relative clearances were compared between VNT and cabozantinib, which were all metabolized by CYP3A4 with the same indications. When combined with ketoconazole, which is a CYP inhibitor, obvious differences were observed in the potency of VNT between different variants, including CYP3A4.2, 15, and 18.

CONCLUSION

This comprehensive assessment of CYP3A4 variants provides significant insights into the allele-specific metabolism of VNT and drug interactions in vitro. We hope that these comprehensive data will provide references and predictions for the clinical application of VNT.

Effects of 27 CYP3A4 protein variants on saxagliptin metabolism in vitro

Saxagliptin is a dipeptidyl peptidase 4 (DPP-4) inhibitor widely used in patients with type 2 diabetes. It can increase the amount of insulin after meals and lower blood sugar. CYP450 3A4 (CYP3A4) can metabolize about 30%-40% of therapeutic drugs. Individual differences caused by CYP3A4 genetic polymorphisms can lead to treatment failure, unpredictable side effects, or severe drug toxicity. The aim of this study was to evaluate the catalytic activities of 27 CYP3A4 variants on saxagliptin metabolism in vitro, which were identified in human CYP alleles. We successfully constructed 27 kinds of wild-type and variant vectors of pFast-dual-OR-3A4 by overlap extension PCR and prepared 27 kinds of CYP3A4 highly expressed cell microsomes by baculovirus insect cell expression system. The ultra-performance liquid chromatography tandem mass spectrometry (UPLC-MS/MS) was used to detect the concentrations of the metabolite of saxagliptin (5-hydroxysaxagliptin) and the internal standard. Compared with the wild-type CYP3A4.1, the intrinsic clearance values of most varieties decreased to 1.91%-77.08%. Most of these varieties showed a decrease in V_max and an increase in Km values compared with wild type. We are the first to report the vitro metabolic data of 27 CYP3A4 variants of the metabolism of saxagliptin which can deepen our understanding of individualized drug use by combining previous studies about the effects of CYP3A4 variants of drug metabolism. With further in vivo studies, we hope it can guide individualized drug use in the clinic when the variants with low metabolic activity to saxagliptin were sequenced in the human body.

Evaluation of Recombinant CYP3A4 Variants on the Metabolism of Oxycodone In Vitro

Cytochrome P450 3A4 is a highly polymorphic enzyme and metabolizes approximately 40%-60% of therapeutic drugs. Its genetic polymorphism may significantly affect the expression and function of CYP3A4 resulting in alterations of the pharmacokinetics and pharmacodynamics of the CYP3A4-mediated drugs. The purpose of this study was to evaluate the catalytic activities of 30 CYP3A4 nonsynonymous variants and wild type toward oxycodone in vitro. CYP3A4 proteins were incubated with oxycodone for 30 min at 37 °C and the reaction was terminated by cooling to -80 °C immediately. Ultraperformance liquid chromatography tandem mass-spectrometry was used to analyze noroxycodone, and kinetic parameters Km, Vmax, and intrinsic clearance (Vmax/Km) of noroxycodone were also determined. Compared with CYP3A4.1, 24 CYP3A4 variants (CYP3A4.2-.5, -.7-.16, -.18 and -.19, -.23 and -.24, -.28 and -.29, and -.31-.34) exhibited significantly decreased relative clearance values (from 4.82% ± 0.31% to 80.98% ± 5.08%), whereas CYP3A4.6, -.17, -.20, -.21, -.26, and -.30 displayed no detectable enzyme activity. As the first study of these alleles for oxycodone metabolism in vitro, results of this study may provide insight into establishing the genotype-phenotype relationship for oxycodone and serve as a reference for clinical administrators and advance the provision of personalized precision medicine.

Functional characteristics of CYP3A4 allelic variants on the metabolism of loperamide in vitro

Background

Cytochrome P450 3A4 (CYP3A4) appears to be genetically polymorphic, which in turn contributes to interindividual variability in response to therapeutic drugs. Loperamide, identified as a CYP3A4 substrate, is prone to misuse and abuse and has high risks of life-threatening cardiotoxicity.

Methods

Thus, this study is designed to evaluate the enzymatic characteristics of 29 CYP3A4 alleles toward loperamide in vitro, including the 7 novel CYP3A4 variants (*28-*34). The incubation system (containing CYP3A4 enzyme, cytochrome b5, 0.5-20 μM loperamide, potassium phosphate buffer and nicotinamide adenine dinucleotide phosphate) was subject to 40-mins incubation at 37°C and the concentrations of N-demethylated loperamide were quantified by UPLC-MS/MS.

Results

As a result, CYP3A4.6, .17, .20 and .30 showed extremely low activity or no activity and the rest of CYP3A4 variants presented varying degrees of decrements in catalytical activities when compared with CYP3A4.1.

Conclusion

As the first study to identify the properties of these CYP3A4 variants toward loperamide metabolism, our investigation may establish the genotype-phenotype relationship for loperamide, predict an individual's capability in response to loperamide, and provide some guidance of clinical medication and treatment for loperamide.

Assessment of Hepatic Cytochrome P450 3A Activity Using Metabolic Markers in Patients with Renal Impairment

BACKGROUND

The renal function of individuals is one of the reasons for the variations in therapeutic response to various drugs. Patients with renal impairment are often exposed to drug toxicity, even with drugs that are usually eliminated by hepatic metabolism. Previous study has reported an increased plasma concentration of indoxyl sulfate and decreased plasma concentration of 4β-hydroxy (OH)-cholesterol in stable kidney transplant recipients, implicating indoxyl sulfate as a cytochrome P450 (CYP) inhibiting factor. In this study, we aimed to evaluate the impact of renal impairment severity-dependent accumulation of indoxyl sulfate on hepatic CYP3A activity using metabolic markers.

METHODS

Sixty-six subjects were enrolled in this study; based on estimated glomerular filtration rate (eGFR), they were classified as having mild, moderate, or severe renal impairment. The plasma concentration of indoxyl sulfate was quantified using liquid chromatography-mass spectrometry (LC-MS). Urinary and plasma markers (6β-OH-cortisol/cortisol, 6β-OH-cortisone/cortisone, 4β-OH-cholesterol) for hepatic CYP3A activity were quantified using gas chromatography-mass spectrometry (GC-MS). The total plasma concentration of cholesterol was measured using the enzymatic colorimetric assay to calculate the 4β-OH-cholesterol/cholesterol ratio. The correlation between variables was assessed using Pearson's correlation test.

RESULTS

There was a significant negative correlation between MDRD eGFR and indoxyl sulfate levels. The levels of urinary 6β-OH-cortisol/cortisol and 6β-OH-cortisone/cortisone as well as plasma 4β-OH-cholesterol and 4β-OH-cholesterol/cholesterol were not correlated with MDRD eGFR and the plasma concentration of indoxyl sulfate.

CONCLUSION

Hepatic CYP3A activity may not be affected by renal impairment-induced accumulation of plasma indoxyl sulfate.

Odanacatib Pharmacokinetics Comparison Between Chinese and Non-Chinese Postmenopausal Women

Odanacatib (ODN), an oral selective inhibitor of cathepsin K, was an investigational agent previously in development for the treatment of osteoporosis. In this phase 1 open-label study, 12 healthy Chinese postmenopausal women received single-dose ODN 50 mg on day 1 and multiple-dose ODN 50 mg once weekly on days 15, 22, 29, and 36 under fasted conditions. Pharmacokinetic (PK) parameters were evaluated on days 1 and 36. Multiple-dose area under the concentration-time profile (AUC_0-168h ) and maximum plasma concentration (C_max ) were compared with historical data from 9 non-Chinese postmenopausal women who also received ODN 50 mg once weekly for 4 weeks. Median time to C_max (t_max ) was 3 and 4 hours following single- and multiple-dose administration, respectively. The arithmetic mean ± SD terminal half-life was 81.0 ± 14.0 and 106.7 ± 14.4 hours following single- and multiple-dose administration, respectively. Comparison of multiple-dose PK parameters showed that the geometric mean ratios (Chinese/non-Chinese) and 95%CIs for AUC_0-168h and C_max were 0.81 (0.55-1.19) and 0.87 (0.69-1.11), respectively. All adverse events were mild, none were serious, and none led to discontinuation. Single- and multiple-dose PKs of ODN 50 mg in Chinese postmenopausal women were generally similar to those previously reported in non-Chinese postmenopausal women.

Systematic screening for CYP3A4 genetic polymorphisms in a Han Chinese population

Aim: To systematically investigate the genetic polymorphisms of the CYP3A4 gene in a Han Chinese population. Materials & methods: The promoter and exons of CYP3A4 gene in 1114 unrelated, healthy Han Chinese subjects were amplified and genotyped by direct sequencing. Results: In total, five previously reported alleles (*1G, *4, *5, *18B and *23) were detected, of which one allele (*23) was reported for the first time in Han Chinese population. Additionally, seven novel exonic variants were also identified and designated as new alleles CYP3A4*28–*34. Conclusion: This study provides the most comprehensive data of CYP3A4 polymorphisms in Han Chinese population and detects the largest number of novel CYP3A4 alleles in one ethnic group.

Effect of CYP3A4 genetic polymorphisms on the genotoxicity of 4,4'-methylene-bis(2-chloroaniline)-exposed workers

OBJECTIVES

We investigated the relationship between 4,4'-methylene-bis(2-chloroaniline) (MBOCA) exposure and micronucleus (MN) frequency, and how this association was affected by genetic polymorphism of the cytochrome P450 enzyme (CYP3A4).

METHODS

We divided the study population into an exposed group (n=44 with total urine MBOCA ≥20 μg/g creatinine) and a control group (n=47 with total urine MBOCA <20 μg/g creatinine). Lymphocyte MN frequency (MNF) and micronucleated cell (MNC) frequency were measured by the cytokinesis-block MN assay method. MNF reported as the number of micronuclei in binucleated cells per 1000 cells, and MNC reported as the number of binucleated cells with the presence of MN per 1000 cells. CYP3A4 alleles were measured by PCR-based restriction fragment length polymorphism (PCR-RFLP).

RESULTS

The mean MNF (6.11 vs 4.46 MN/1000 cells, p<0.001) and MNC (5.75 vs 4.15 MN/1000 cells, p<0.001) in the exposed workers was significantly higher than that in the controls. The CYP3A4 polymorphism A/A+A/G influenced the difference in the mean MNF (5.97 vs 4.38 MN/1000 cells, p<0.001) and MNC (5.60 vs 4.15 MN/1000 cells, p<0.001) between the MBOCA-exposed and control groups. After adjusting risk factors, the MNF level in the MBOCA-exposed workers was 0.520 MN cells/1000 cells (p<0.001) higher than the control group among the CYP3A4 A/A+A/G genotype. Similarly, the MNC level in the MBOCA-exposed workers was 0.593 MN/1000 cells (p<0.001) higher than the control group among the CYP3A4 A/A+A/G genotype. However, the difference in adjusted MNF and MNC between the exposed and control groups was not significant for the CYP3A4 polymorphism with the G/G genotype.

CONCLUSIONS

We recommend that lymphocytes MNF and MNC are good indicators to evaluate MBOCA genotoxicity. Individuals with the CYP3A4 polymorphism A/A and A/G genotypes appear to be more susceptible to MBOCA genotoxicity.

Fast Versus Slow Strategy of Switching Patients With Schizophrenia to Aripiprazole From Other Antipsychotics

This study aimed to compare strategies differing in the speed of switching schizophrenic patients to aripiprazole from other antipsychotic agents, with dual administration for 2 weeks and then tapering off the current antipsychotic in fast (within 1 week) versus slow (within 4 weeks) strategies. This 8-week, open-label, randomized, parallel study assigned patients with a primary Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition, diagnosis of schizophrenia or schizoaffective disorder to either the fast-switching (n = 38) or slow-switching (n = 41) group. Efficacy assessments at 5 time points included Positive and Negative Syndrome Scale and Clinical Global Impression scale. Safety assessments included extrapyramidal symptoms, metabolic profile, serum prolactin level, QTc interval, and adverse events. Drug concentrations and cytochrome P450 CYP2D6 and CYP3A4 genotypes were also measured. The fast- and slow-switching groups were comparable in demographical and clinical features at baseline and dropout rate. In the intention-to-treat analysis using mixed-effects models, there were significant within-group decreases over time in the Positive and Negative Syndrome Scale total scores (P = 0.03) and its subscores except for positive subscores, whereas no between-group differences were found. A reduction in body weight (P = 0.01) and lower levels of total cholesterol (P = 0.03), triglycerides (P = 0.03), and prolactin (P = 0.01) were noted in both groups but no increase in extrapyramidal symptoms or prolongation of QTc. The blood concentrations of aripiprazole in all patients were in a therapeutic range at day 56, with CYP2D6*10 polymorphisms being associated with aripiprazole concentrations. In conclusion, there is no significant difference between the fast- and slow-switching strategy in terms of improvements in clinical symptoms and metabolic profile in this 8-week study.

CYP3A5*3 and MDR1 C3435T are influencing factors of inter-subject variability in rupatadine pharmacokinetics in healthy Chinese volunteers

Rupatadine (RUP) is an oral antihistamine and platelet-activating factor antagonist and is shown as the substrate of CYP3A5 and P-gp. The significant interindividual differences of CYP3A5 and P-gp often cause bioavailability differences of some clinical drugs. The present study is aimed to evaluate the effect of genetic polymorphisms of CYP3A5 and MDR1 on RUP pharmacokinetics in healthy male Chinese volunteer subjects. Blood samples were collected from 36 subjects before and after a single, oral RUP 10 mg dose. A PCR-RFLP assay was used to genotype CYP3A5*3 and assess MDR1 C3435T variation. A validated LC-MS/MS method quantified plasma RUP concentration. The relationship between RUP plasma concentration, pharmacokinetic parameters, and polymorphic alleles (CYP3A5 and MDR1) were assessed. Plasma RUP concentrations were lower for CYP3A5*1/*1 carriers than for CYP3A5*3/*3 and CYP3A5*1/*3 carriers. Mean C(max), AUC(0-t) and AUC(0-∞) were significantly lower, and the CLz and Vd were significantly higher in the CYP3A5 wild-type group, than in the CYP3A5 mutated group. MDR1 CT and MDR1 TT carriers had lower plasma RUP concentrations than MDR1 CC carriers. The mean C(max), AUC(0-t), AUC(0-∞) and T max were significantly lower in the TT group than in the CC and CT groups. The mean CLz was higher in the TT group than in the CC and CT groups, but not significantly. These results suggest that CYP3A5 and MDR1 may play a key role in the variability of RUP metabolism and transport, respectively. CYP3A5 and MDR1 polymorphisms may be the main explanation for the differences observed in RUP pharmacokinetics, and therefore may provide a rationale for safe and effective clinical use of RUP. Our research lays down a solid theory foundation to guide the safe and effective clinical use of RUP and a route to achieve individualized therapy.

The pharmacokinetics of ilaprazole for gastro-esophageal reflux treatment

INTRODUCTION

Approximately 20% of the Western population is affected by gastro-esophageal reflux disease (GERD). To date, proton pump inhibitors (PPIs) represent the mainstay of GERD medical treatment. However, despite their undoubted benefit, about 40% of GERD patients display an inadequate response to these drugs. Recently, a new PPI, ilaprazole , at oral doses of 10 mg has shown higher suppression of gastric acid secretion, more prolonged plasma half-life, and similar safety compared to 20 mg omeprazole.

AREAS COVERED

This review provides an update on the following points: pharmacokinetic profile and metabolism of ilaprazole in relation to its pharmacodynamic properties; comparative data on the pharmacokinetics and pharmacodynamics of ilaprazole with currently available PPIs; and implications for studies on the therapeutic efficacy of ilaprazole in GERD.

EXPERT OPINION

Different studies show that ilaprazole, a benzimidazole derivative, has an extended plasma half-life in comparison with all other approved PPIs. In addition, ilaprazole metabolism is not significantly influenced by CYP2C19, compared to the available PPIs. Furthermore, the pharmacological characteristics of ilaprazole confer theoretical advantages that are expected to translate into an improved acid control, particularly at night time. However, studies comparing the clinical pharmacokinetics and pharmacodynamics of ilaprazole with those of second-generation PPIs are insufficient. Moreover, further investigations assessing the efficacy of ilaprazole in the management of GERD are required. In healthy volunteers, as well as in patients with gastric or duodenal ulcers, ilaprazole has not shown clinically relevant changes in hematology and biochemistry testing, nor significant treatment-related adverse symptoms.

Pharmacogenetics of pain and analgesia

Pain severity ratings and the analgesic dosing requirements of patients with apparently similar pain conditions may differ considerably between individuals. Contributing factors include those of genetic and environmental origin with epigenetic mechanisms that enable dynamic gene-environment interaction, more recently implicated in pain modulation. Insight into genetic factors underpinning inter-patient variability in pain sensitivity has come from rodent heritability studies as well as familial aggregation and twin studies in humans. Indeed, more than 350 candidate pain genes have been identified as potentially contributing to heritable differences in pain sensitivity. A large number of genetic association studies conducted in patients with a variety of clinical pain types or in humans exposed to experimentally induced pain stimuli in the laboratory setting, have examined the impact of single-nucleotide polymorphisms in various target genes on pain sensitivity and/or analgesic dosing requirements. However, the findings of such studies have generally failed to replicate or have been only partially replicated by independent investigators. Deficiencies in study conduct including use of small sample size, inappropriate statistical methods and inadequate attention to the possibility that between-study differences in environmental factors may alter pain phenotypes through epigenetic mechanisms, have been identified as being significant.

Identification of human cytochrome P450 enzymes involved in the metabolism of a novel к-opioid receptor agonist, nalfurafine hydrochloride

Nalfurafine hydrochloride (TRK-820) exhibits strong к-opioid agonistic activity and is a new antipruritic agent for uremic pruritus. This study was performed to identify the human hepatic cytochrome P450 isoforms involved in the metabolic conversion of nalfurafine to the decyclopropylmethylated form, de-CPM, using human liver microsomes and E. coli membrane fractions expressing human P450 isoforms. Samples were analysed by liquid chromatography with a radioactivity detector and liquid chromatography-tandem mass spectrometry. The metabolism of nalfurafine by human liver microsomes exhibited a biphasic kinetic profile. Experiments examining the metabolism by E. coli membrane fractions expressing human P450 isoforms indicated that CYP1A1, 2C8, 2C19 and 3A4 had the ability to produce de-CPM. In experiments with human liver microsomes that examined the inhibition of nalfurafine metabolism by anti-human P450 antibodies, anti-CYP3A4 antibody predominantly, and anti-CYP2C8 and 2C19 antibodies moderately, inhibited de-CPM formation. From these results, CYP3A4 appeared to be the major isoform involved in the metabolic decyclopropylmethylation of nalfurafine, while CYP2C8 and 2C19 most likely play a minor role in the formation of de-CPM.

Pain, analgesia and genetics

OBJECTIVES

In the clinical setting, there is marked intersubject variability in the intensity of pain reported by patients with apparently similar pain states, as well as widely differing analgesic dosing requirements between individuals to produce satisfactory pain relief with tolerable side-effects. Genetic and environmental factors as well as their interaction are implicated, and these are discussed in this review.

KEY FINDINGS

Pioneering work undertaken in mice more than a decade ago, showed a strong genetic contribution to levels of nociception/hypersensitivity as well as levels of antinociception produced by commonly available analgesic agents. To date more than 300 candidate 'pain' genes have been identified as potentially contributing to heritable differences in pain sensitivity and analgesic responsiveness in animals and humans, with this information available in a publicly accessible database http://www.jbldesign.com/jmogil/enter.html. Since then, many genetic association studies have been conducted in humans to investigate the possibility that single nucleotide polymorphisms (SNPs) in an individual gene may explain drug inefficacy or excessive toxicity experienced by a small subset of the whole population who have the rare allele for a particular SNP.

SUMMARY

Despite the fact that SNPs in more than 20 genes that affect pain sensitivity or contribute to interindividual variability in responses to analgesic medications have been identified in the human genome, much of the data is conflicting. Apart from deficiencies in the design and conduct of human genetic association studies, recent research from other fields has implicated epigenetic mechanisms that facilitate dynamic gene-environment communication, as a possible explanation.

Effect of CYP3A4*1G on the fentanyl consumption for intravenous patient-controlled analgesia after total abdominal hysterectomy in Chinese Han population

WHAT IS KNOWN AND OBJECTIVE

  Clinical investigations into postoperative intravenous patient-controlled analgesia (PCA) have indicated interindividual differences in fentanyl consumption. Cytochrome P450 3A4 (CYP3A4) is the main metabolism enzyme of fentanyl, and single nucleotide polymorphisms within the CYP3A4 gene may contribute to the variability of fentanyl analgesic efficacy. The aim of this study was to investigate whether the most common genetic variation in Chinese, CYP3A4*1G, has an impact on the fentanyl consumption for intravenous PCA in Chinese Han women undergone abdominal total hysterectomy.

METHODS

A total of 79 female patients (American Society of Anesthesiologist physical status I or II) scheduled to undergo elective abdominal total hysterectomy were enrolled. All patients received combined spinal-epidural anaesthesia with bupivacaine. Intravenous fentanyl PCA was provided postoperatively for satisfactory analgesia. The doses of fentanyl consumption were recorded 2, 4, 24 and 48 h after the initiation of PCA postoperatively. Pain at rest and adverse effects were measured with rating scales. CYP3A4*1G was screened by means of direct sequencing and further confirmed by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP).

RESULTS AND DISCUSSION

Forty-six patients were GG homozygotes, 27 patients were GA heterozygotes, and six patients were AA homozygotes, respectively. The distribution of the CYP3A4*1G allele was consistent with Hardy-Weinberg equilibrium (P>0·05). At 2 and 4 h, the doses of fentanyl required for patients with GA/AA genotypes were 80·0 (45·0, 112·5) μg and 120·0 (80, 173·8)μg, respectively, and significantly lower than those for GG homozygotes [91·3 (80·0, 125·0) μg and 169·0 (112·5, 226·3) μg, respectively, P<0·05]. There was trend of decreasing fentanyl consumption at 24 and 48h in patients with GA/AA genotypes, relative to GG homozygotes, but the difference was not statistical significant (P>0·05).

WHAT IS NEW AND CONCLUSIONS

CYP3A4*1G has an impact on the analgesic effect of fentanyl in Chinese Han subjects. Further validation of our results in a well-powered study would be helpful.

Analysis of CYP3A4 genetic polymorphisms in Han Chinese

Our study aimed to comprehensively investigate the genetic polymorphisms of CYP3A4 in Han Chinese. We sequenced the gene regions of CYP3A4, including its promoter, exons, surrounding introns and 3' untranslated region (3'UTR), from 100 unrelated-healthy Han Chinese individuals. We detected 11 SNPs, three of which are novel. According to in silico functional prediction of novel variants, 20148 A>G in exon 10, resulting in substitution of Tyr319 with Cys (CYP3A4*21), may induce dramatic alteration of protein conformation, and 26908 G>A in 3'UTR may disrupt post-transcriptional regulation. We identified five alleles in Han Chinese, the allele frequencies of CYP3A4*1, *5, *6, *18 and *21 are 97, 0.5, 1, 1 and 0.5%, respectively. Haplotype inference revealed 14 haplotypes, of which the major haplotype CYP3A4*1A constitutes 59% of the total chromosomes. We also examined the possible role of natural selection in shaping the variation of CYP3A4 and confirmed a trend, consistent with the action of positive selection. We systematically screened the genetic polymorphisms of CYP3A4 in Han Chinese, highlighted possible functional impairment of the novel allele and summarized the distinct allele and haplotype frequency distribution, with an emphasis on detecting the footprint of recent positive selection on the CYP3A4 gene in Han Chinese.

Microvalve and micropump controlled shuttle flow microfluidic device for rapid DNA hybridization

We present a novel microfluidic device integrated with microvalves and micropumps for rapid DNA hybridization using shuttle flow. The device is composed of 48 hybridization units containing 48 microvalves and 96 micropumps for the automation of shuttle flow. We used four serotypes of Dengue Virus genes (18mer) to demonstrate that the automatic shuttle flow shortened the hybridization time to 90 s, reduced sample consumption to 1 μL and lowered detection limit to 100 pM (100 amol in a 1 μL sample). Moreover, we applied this device to realize single base discrimination and analyze 48 samples containing different DNA targets, simultaneously. For kinetic measurements of nucleotide hybridization, on-line monitoring of the processes was carried out. This rapid hybridization device has the ability for accommodating the entire hybridization process (i.e., injection, hybridization, washing, detection, signal acquisition) in an automated and high-throughput fashion.

Genetic determinants of statin-associated myopathy

Lipid-lowering drugs, especially 3-hydroxy-3-methylglutaryl coenzyme A inhibitors (statins), are widely used in the treatment of patients with increased risk of cardiovascular disease, with well-documented benefits. However, in rare cases, lipid-lowering drugs may cause myopathy or rhabdomyolysis, the risk of which is increased by certain drug–drug interactions. Polymorphisms of metabolizing pathways, including CYP, and efflux transporters, such as MDR1 and SLCO1B1, may cause intersubject variability in plasma statin levels and therefore may be responsible for susceptibility to myopathy. The aim of this review is to summarize selected genetic polymorphisms that predispose to statin-related myopathy (including combined studies of myopathy and myalgia). Genome-wide studies suggest that there is a strong candidate variant within the SLCO1B1 gene (rs4149056) for statin-associated myopathy in a UK (European) population. An enhanced understanding of statin-related myopathy may lead to safer drug development and use.

Pharmacokinetics of the new proton pump inhibitor ilaprazole in Chinese healthy subjects in relation to CYP3A5 and CYP2C19 genotypes

BACKGROUND

PPIs are widely used in peptic diseases, and this paper is to investigate the kinetic characteristics of a new PPI ilaprazole in Chinese healthy subjects and the association with CYP3A5 and CYP2C19 polymorphisms.

METHODS

21 subjects were selected and treated with 10mg ilaprazole according to their CYP3A5*3 genotypes (including 7 of CYP3A5*1/*1, 7 of *1/*3, and 7 of *3/*3). The plasma concentrations of ilaprazole and its metabolites were monitored by LC-MS/MS method.

RESULTS

The C(max), AUC((0-6)), AUC((0-48)) and AUC((0-infinity)) of ilaprazole were all significantly different across the 3 CYP3A5 genotypes (including 4 of CYP3A5*1/*1, 4 of *1/*3, 3 of *3/*3; P<0.05) in CYP2C19 wild-type subjects (CYP2C19 wt/wts), similar variety of C(max) and AUC((0-6)) among CYP3A5 genotypes (including 3 of CYP3A5*1/*1, 3 of *1/*3, 4 of *3/*3; P<0.05) were also observed in CYP2C19 heterozygous subjects (CYP2C19 wt/mts). The sulfoxidation metabolic index (measure of collective CYP3A activity) indicates that the CYP3A5*1/*1, (high-expressers), *1/*3, (low-expressers), and *3/*3 (no-expressers) groups have medium, lowest and highest activities on ilaprazole metabolism, inconsistent with genotype-based CYP3A5 enzymatic activity. Further analysis showed no correlation between ilaprazole metabolism and CYP2C19 genotypes, evidenced by that the AUC((0-infinity)) of ilaprazole from either CYP3A5*1/*1 or CYP3A5*1/*3 groups was much higher in CYP2C19 wt/wts (n=4) than that in CYP2C19 wt/mts (n=3) (P<0.001), but the C(max) and AUC((0-6)) of ilaprazole from CYP3A5*3/*3 groups, were significantly lower in CYP2C19 wt/wts (n=3) compared to CYP2C19 wt/mts (n=4) (P<0.01).

CONCLUSIONS

There was no demonstrated relationship between ilaprazole metabolism and CYP3A5 polymorphisms.

Toward individualized treatment: prediction of anticancer drug disposition and toxicity with pharmacogenetics

A great deal of effort has been spent in defining the pharmacokinetics and pharmacodynamics of investigational and registered anticancer agents. Often, there is a marked variability in drug handling between individual patients, which contributes to variability in the pharmacodynamic effects of a given dose of a drug. A combination of physiological variables, genetic characteristics (pharmacogenetics) and environmental factors is known to alter the relationship between the absolute dose and the concentration-time profile in plasma. A variety of strategies are now being evaluated in patients with cancer to improve the therapeutic index of anticancer drugs by implementation of pharmacogenetic imprinting through genotyping or phenotyping individual patients. The efforts have mainly focused on variants in genes encoding the drug-metabolizing enzymes thiopurine S-methyltransferase, dihydropyrimidine dehydrogenase, members of the cytochrome P450 family, including the CYP2B, 2C, 2D and 3A subfamilies, members of the UDP glucuronosyltransferase family, as well as the ATP-binding cassette transporters ABCB1 (P-glycoprotein) and ABCG2 (breast cancer resistance protein). Several of these genotyping strategies have been shown to have substantial impact on therapeutic outcome and should eventually lead to improved anticancer chemotherapy.