ABCG2 polymorphism is associated with the low-density lipoprotein cholesterol response to rosuvastatin

Seventeen years of statin pharmacogenetics: a systematic review

AIM

We evaluated the evidence of pharmacogenetic associations with statins in a systematic review.

METHODS

Two separate outcomes were considered of interest: modification of low-density lipoprotein cholesterol (LDL-C) response and modification of risk for cardiovascular events.

RESULTS

In candidate gene studies, 141 loci were claimed to be associated with LDL-C response. Only 5% of these associations were positively replicated. In addition, six genome-wide association studies of LDL-C response identified common SNPs in APOE, LPA, SLCO1B1, SORT1 and ABCG2 at genome-wide significance. None of the investigated SNPs consistently affected the risk reduction for cardiovascular events.

CONCLUSION

Only five genetic loci were consistently associated with LDL-C response. However, as effect sizes are modest, there is no evidence for the value of genetic testing in clinical practice.

Function-impairing polymorphisms of the hepatic uptake transporter SLCO1B1 modify the therapeutic efficacy of statins in a population-based cohort

BACKGROUND

The efficacy of statins, which are used commonly in primary and secondary prevention of cardiovascular diseases, shows a wide range of interindividual variability. Genetic variants of OATP1B1, a hepatic uptake transporter, can modify access of statins to its therapeutic target, thereby potentially altering drug efficacy. We studied the impact of genetic variants of OATP1B1 on the lipid-lowering efficacy of statins in a population-based setting.

MATERIALS AND METHODS

The basis of the analysis was the Study of Health in Pomerania, a cohort of 2732 men and women aged 20-81 years. Included in the statistical analysis to evaluate the impact of OATP1B1 on therapeutic efficacy of statins were 214 individuals diagnosed with dyslipidaemia during initial recruitment and receiving statins during the 5-year follow-up.

RESULTS

Analysing the impact of the OATP1B1 genotype, we observed a trend for lower statin-induced total cholesterol reduction in carriers of the SLCO1B1 512C variant. Restricting the analysis to patients receiving simvastatin, pravastatin, lovastatin and fluvastatin indicated a statistically significant association of the OATP1B1 genotype on lipid parameters at the 5-year follow-up. No such effect was observed for atorvastatin. Calculation of achievement of treatment goals according to the NCEP-ATPIII guidelines showed a lower rate of successful treatment when harbouring the mutant allele for patients taking simvastatin (46.7 vs. 73.9%). A similar trend was observed for pravastatin (34.4 vs. 70.4%).

CONCLUSION

Genetic variants of OATP1B1 leading to impaired hepatic uptake of statins translated into reduced drug efficacy in a population-based cohort.

Achievement of specified lipid and high-sensitivity C-reactive protein levels with two statins in Chinese patients with hypercholesterolaemia

Background

Statins reduce plasma low-density lipoprotein cholesterol (LDL-C) and high-sensitivity C-reactive protein (hsCRP) levels. Rosuvastatin 10 mg daily appears to be more potent in reducing LDL-C than simvastatin 40 mg, but the relative effect of these two statin doses on hsCRP is unknown.

Methods

Chinese hyperlipidaemic patients with high cardiovascular risk or familial hypercholesterolaemia (FH) were treated with rosuvastatin 10 mg and simvastatin 40 mg daily in an open-label crossover study. Lipid profiles were measured off treatment and after at least 4 weeks treatment with each of the two statins and hsCRP levels were measured on treatment with both statins.

Results

Both treatments were well tolerated in 247 patients (age 55.7 ± 11.1 years; 100 male; 140 with FH) with good treatment compliance. There were statistically significant differences (P < 0.001) for rosuvastatin versus simvastatin for LDL-C reduction (−52.4 ± 11.9 % vs. -47.7 ± 10.8 %) and on-treatment LDL-C (2.62 ± 0.99 mmol/L vs. 2.86 ± 0.97 mmol/L), respectively, but the on-treatment hsCRP levels (1.33 ± 1.37 mg/L vs. 1.41 ± 1.57 mg/L, P > 0.05) were not significantly different. The lipid target (LDL-C <2.6 mmol/L) was achieved by 52.9 % with rosuvastatin compared with 42.6 % with simvastatin (P < 0.05). The proportions of patients attaining hsCRP targets of <2 and <1 mg/L were similar with the two statins (57.1 % and 74.6 % for rosuvastatin vs. 57.1 % and 80.1 % for simvastatin, P > 0.05).

Conclusion

A significantly greater proportion of patients achieved LDL-C targets with rosuvastatin 10 mg compared to simvastatin 40 mg in Chinese patients with hypercholesterolaemia, but there was no significant difference in achieving hsCRP target levels with the two statins.

Marked Alteration of Rosuvastatin Pharmacokinetics in Healthy Chinese with ABCG2 34G>A and 421C>A Homozygote or Compound Heterozygote

Rosuvastatin, a 3-hydroxy-3-methylglutaryl-coenzyme A reductase inhibitor used to lower blood low-density lipoprotein cholesterol, is a substrate of the membrane ABCG2 exporter. ABCG2 variants have been shown to alter rosuvastatin disposition. The objective of this study is to determine the impact of ABCG2 34/421 compound haplotypes on rosuvastatin pharmacokinetics in healthy Chinese volunteer subjects. Eight hundred healthy Chinese males were genotyped by polymerase chain reaction-pyrosequencing for ABCG2 34G>A, ABCG2 421C>A, SLCO1B1 521T>C, and CYP2C9*3 variants. Sixty-two male subjects with wild-type SLCO1B1 c.521TT and CYP2C9*3 were recruited for this pharmacokinetic study of rosuvastatin. A single oral dose of 10 mg rosuvastatin was administrated to each subject, and blood samples were collected before and at various time points after drug administration. Plasma concentration of rosuvastatin was determined by high-performance liquid chromatography-tandem mass spectrometry, and pharmacokinetic analysis was carried out using the WinNonlin program. In Chinese males, high allele frequency of ABCG2 c.34G>A (0.275) and c.421C>A (0.282) was observed, resulting in a considerable portion (23.3%) of subjects being ABCG2 34/421 compound heterozygotes. Compared with subjects with ABCG2 wild-type (c.34GG/421CC), plasma rosuvastatin Cmax and area under the curve, AUC0-∞, were significantly higher, while the apparent oral clearance, CL/F, was significantly lower in subjects with c.34AA, c.421AA, and c.34GA/421CA genotypes. Both t1/2 and Tmax were similar among subjects with different genotypes. A high frequency of ABCG2 c.34G>A and c.421C>A variants was present in Chinese males, and the disposition of rosuvastatin was significantly affected by both variants. These data suggest that it is advisable to genotype these variants when prescribing rosuvastatin to Chinese subjects, leading to a precise dose for each individual.

Effects of phenotypic and genotypic factors on the lipid responses to niacin in Chinese patients with dyslipidemia

The acyl-CoA:diacylglycerol acyltransferase (DGAT) enzymes DGAT1 and DGAT2 catalyze the final step in triglycerides biosynthesis. This study examined the relationships of baseline phenotypes and the common polymorphisms in DGAT1 and DGAT2 with the lipid responses to niacin.Lipid responses in Chinese patients with dyslipidemia treated with the extended release (ER) niacin/laropiprant combination 1000/20 mg for 4 weeks and then 2000/40 mg for 8 weeks (n = 121, the primary study) or with ER niacin 1500 mg for at least 4 weeks (n = 68, the replication study) were analyzed according to genotypes of DGAT1 rs7003945 T>C and DGAT2 rs3060 T>C polymorphisms.Treatment with ER niacin improved all lipid parameters in both studies. Absolute and percentage changes in lipids were related to their baseline levels, particularly for low-density lipoprotein cholesterol (LDL-C). The DGAT2 rs3060 T>C polymorphism was associated with lower baseline LDL-C, apoB, high-density lipoprotein cholesterol (HDL-C), and apoAI in patients on statin therapy in the primary study. Subjects with the DGAT2 rs3060 T>C variant had less reduction in LDL-C in the primary study and smaller changes in triglyceride and HDL-C in the replication study but these associations became non-significant after adjusting for baseline lipid values. The DGAT1 rs7003945 T>C polymorphism was not related to lipid baseline values or changes in either study. Concomitant statin therapy and lower body weight were also associated with greater reduction in LDL-C.Baseline lipid levels were the main determinants of lipid responses especially for LDL-C. The DGAT2 rs3060 polymorphism might influence the lipid responses depending on baseline phenotype, but this association did not persist after adjustment for the baseline lipid levels.

Intestinal and hepatic drug transporters: pharmacokinetic, pathophysiological, and pharmacogenetic roles

The efficacy and safety of pharmacotherapies are determined by the complex processes involved in the interactions between drugs with the human body, including pharmacokinetic aspects. Among pharmacokinetic factors, it has been recognized that drug transporters play critical roles for absorption, distribution and excretion of drugs, regulating the membrane transport of drugs. The vast amounts of information on drug transporters collected in the past 20 years have been organized according to biochemical, molecular, genetic, and clinical analyses. Novel technologies, public databases, and regulatory guidelines have advanced the use of such information in drug development and clinical practice. In this review, we selected some clinically important drug transporters expressed in the intestine and liver, and introduced the research history and current knowledge of their pharmacokinetic, pathophysiological, and pharmacogenetic implications.

Quantitative Analysis of the ABCG2 c.421C>A Polymorphism Effect on In Vivo Transport Activity of Breast Cancer Resistance Protein (BCRP) Using an Intestinal Absorption Model

ABCG2 c.421C>A is one of the most frequent polymorphisms in ABCG2, which encodes the breast cancer resistance protein (BCRP). Clinical pharmacogenetic studies have shown that the plasma area under the concentration-time curve (AUC) values after oral administration of BCRP substrate drugs are significantly higher in subjects homozygous for the c.421C>A polymorphism (421AA) than in wild-type subjects (421CC). The aim of this study was to quantitatively estimate the in vivo decrease of BCRP function caused by the c.421C>A polymorphism based on clinical pharmacokinetic data. Assuming that the pharmacokinetic alteration is accounted for by intestinal BCRP, the ratio of the transport activity of the mutated BCRP to that of the wild-type was optimized by comparing calculations from an intestinal absorption model and clinical pharmacokinetic data. In conclusion, the in vivo intestinal BCRP transport activity in 421AA subjects is estimated to be approximately 23% of that in the 421CC subjects.

In Vitro Screening of Environmental Chemicals Identifies Zearalenone as a Novel Substrate of the Placental BCRP/ABCG2 Transporter

The BCRP (ABCG2) transporter is responsible for the efflux of chemicals from the placenta to the maternal circulation. Inhibition of BCRP activity could enhance exposure of offspring to environmental chemicals leading to altered reproductive, endocrine, and metabolic development. The purpose of this study was to characterize environmental chemicals as potential substrates and inhibitors of the human placental BCRP transporter. The interaction of BCRP with a panel of environmental chemicals was assessed using the ATPase and inverted plasma membrane vesicle assays as well as a cell-based fluorescent substrate competition assay. Human HEK cells transfected with wild-type BCRP or the Q141K genetic variant, as well as BeWo placental cells that endogenously express BCRP were used to further test inhibitor and substrate interactions. To varying degrees, the eleven chemicals inhibited BCRP activity in activated ATPase membranes and inverted membrane vesicles. Further, genistein, zearalenone, and tributyltin increased the retention of the fluorescent BCRP substrate, Hoechst 33342, between 50-100% in BeWo cells. Additional experiments characterized the mycotoxin and environmental estrogen, zearalenone, as a novel substrate and inhibitor of BCRP in WT-BCRP and BeWo cells. Interestingly, the BCRP genetic variant Q141K exhibited reduced efflux of zearalenone compared to the wild-type protein. Taken together, screening assays and direct quantification experiments identified zearalenone as a novel human BCRP substrate. Additional in vivo studies are needed to directly determine whether placental BCRP prevents fetal exposure to zearalenone.

Effect of CYP2C19 polymorphism on the pharmacokinetics of rosuvastatin in healthy Taiwanese subjects

CYP2C19 contributes to N-desmethyl rosuvastatin formation in "in vitro" models. Approximately 80% of Taiwanese are CYP2C19 extensive metabolizers (EMs, CYP2C19*1/*1, *1/*2, or *1/*3). We studied the potential effect of CYP2C19 genotypes on rosuvastatin pharmacokinetics in healthy Taiwanese subjects following single and multiple daily oral doses of rosuvastatin calcium (20 mg). Geometric mean ratios for poor metabolizers (PMs): EMs for rosuvastatin were 0.974 and 0.872 for area under the curve and maximum plasma concentration on day 1 (1.01 and 0.965 on day 17) and for N-desmethyl rosuvastatin, 1.21 and 1.07 on day 1 (1.14 and 1.09 on day 17), respectively. Changes of lipid profiles from baseline to day 18 for PMs and EMs were -52.4% and -53.3% (low-density lipoprotein cholesterol), and -34.2% and -30.0% (total cholesterol), respectively. Rosuvastatin was generally well-tolerated by both PMs and EMs. These results suggest that CYP2C19 polymorphism does not affect rosuvastatin pharmacokinetics in healthy Taiwanese in a clinically meaningful way.

Polymorphisms of the drug transporters ABCB1, ABCG2, ABCC2 and ABCC3 and their impact on drug bioavailability and clinical relevance

INTRODUCTION

Human ATP-binding cassette (ABC) transporters act as translocators of numerous substrates across extracellular and intracellular membranes, thereby contributing to bioavailability and consequently therapy response. Genetic polymorphisms are considered as critical determinants of expression level or activity and subsequently response to selected drugs.

AREAS COVERED

Here the influence of polymorphisms of the prominent ABC transporters P-glycoprotein (MDR1, ABCB1), breast cancer resistance protein (BCRP, ABCG2) and the multidrug resistance-associated protein (MRP) 2 (ABCC2) as well as MRP3 (ABCC3) on the pharmacokinetic of drugs and associated consequences on therapy response and clinical outcome is discussed.

EXPERT OPINION

ABC transporter genetic variants were assumed to affect interindividual differences in pharmacokinetics and subsequently clinical response. However, decades of medical research have not yielded in distinct and unconfined reproducible outcomes. Despite some unique results, the majority were inconsistent and dependent on the analyzed cohort or study design. Therefore, variability of bioavailability and drug response may be attributed only by a small amount to polymorphisms in transporter genes, whereas transcriptional regulation or post-transcriptional modification seems to be more critical. In our opinion, currently identified genetic variants of ABC efflux transporters can give some hints on the role of transporters at interfaces but are less suitable as biomarkers to predict therapeutic outcome.

Pharmacokinetic interaction between rosuvastatin and metformin in healthy Korean male volunteers: a randomized, open-label, 3-period, crossover, multiple-dose study

PURPOSE

Rosuvastatin is indicated for hypercholesterolemia or dyslipidemia and metformin mainly for type 2 diabetes. These 2 drugs are frequently prescribed in combination due to the high comorbidity of the 2 diseases. However the nature of pharmacokinetic interaction between the 2 drugs has not been previously investigated. The purpose of our study was to investigate the pharmacokinetic interaction between rosuvastatin and metformin in healthy Korean male volunteers.

METHODS

This was a randomized, open-label, 6-sequence, 3-period, crossover, multiple-dose study. Eligible subjects, aged 20 to 50 years and within 20% of the ideal body weight, received 1 of the following 3 treatments for each period once daily for 5 consecutive days with a 10-day washout period between the treatments: monoadministration of rosuvastatin 10 mg tablet, monoadministration of metformin 750 mg tablet, and coadministration of rosuvastatin 10 mg tablet with metformin 750 mg tablet. Blood samples were collected up to 72 hours after the last dose and pharmacokinetic parameters for rosuvastatin and metformin were compared between combination and monotherapy. Adverse events were investigated and evaluated based on subject interviews and physical examinations.

FINDINGS

Among the 36 enrolled subjects, 31 completed the study. The coadministration of rosuvastatin with metformin produced a significant pharmacokinetic interaction in rosuvastatin Css,max, with the 90% CI for the geometric mean ratio (coadministration:monoadministration) being 110.27% to 136.39% (P = 0.0029), whereas no significant interaction was observed in rosuvastatin AUCtau, yielding the 90% CI of 104.41% to 118.95%. When metformin was coadministered with rosuvastatin, no significant pharmacokinetic interaction was observed for Css,max and AUCtau of metformin, yielding the 90% CIs of the geometric mean ratio for coadministration to monoadministration as 87.38% to 102.54% and 86.70% to 99.08%, respectively. Overall, 19 mild and 1 moderate adverse events occurred in 12 subjects, with no significant differences in the incidence among the 3 treatments.

IMPLICATIONS

Although the Css,max of rosuvastatin was significantly influenced by coadministration with metformin, the degree of interaction seen was considered clinically insignificant, with no significant interaction observed in the other pharmacokinetic measures between the 2 drugs. These results imply that drug effects of rosuvastatin and metformin will also not be significantly influenced by coadministration of the 2 drugs. All treatments were well tolerated and no serious adverse events occurred. ClinicalTrials.gov identifier: NCT01526317.

Expression and activity of ABCG2, but not ABCB1 or OATP1B1, are associated with cholesterol levels: evidence from in vitro and in vivo experiments

Aim: This study investigated whether cholesterol levels influence the expression and function of drug transporters and whether statin treatments could alter this by reducing plasma low-density lipoprotein cholesterol levels. Patients & methods: The mRNA expression and function of OATP1B1, ABCB1 and ABCG2 were assessed in peripheral blood mononuclear cells (PBMCs) of healthy subjects and from patients with familial hypercholesterolemia (FH) before and after statin treatment by real-time PCR and flow cytometric assay, respectively. The effects of statin exposure and cholesterol depletion in PBMCs and in cell lines were assessed. Results: ABCG2 expression and activity in PBMCs in patients with FH were 2-fold and 26-fold higher, respectively, than those of the healthy subjects (p < 0.001 for both). Statin treatment decreased ABCG2 expression and function in patients with FH. Depletion of cholesterol ex vivo reduced ABCG2 expression in PBMCs and reduced ABCG2 activity in liver and colon cells. Conclusion: This study suggested that statins may downregulate ABCG2 expression and function through reducing low-density lipoprotein cholesterol levels.

Original submitted 25 November 2013; Revision submitted 21 March 2014

Pharmacogenomics, lipid disorders, and treatment options

Statins form the backbone of lipid-lowering therapy in the prevention of cardiovascular disease. Numerous studies have evaluated the effect of genomics on the clinical efficacy and adverse effects of statins. Several gene variants that can be linked to either the pharmacokinetics or pharmacodynamics of statins have been identified as potentially important, although there are some discrepant findings among studies. Effect sizes are modest for lipid-lowering efficacy and perhaps somewhat larger for risk of myopathy, although results are inconsistent. Pharmacogenomics of nonstatin lipid-lowering agents have not been evaluated to the same extent, given their relatively limited use, although there are some promising candidate genes for further study. Finally, with several new classes of lipid-lowering therapies soon becoming available, there may be a potential application for pharmacogenomics to identify patients ideally suited to receive-or those who should avoid-specific medications.

Effects of polymorphisms in ABCG2, SLCO1B1, SLC10A1 and CYP2C9/19 on plasma concentrations of rosuvastatin and lipid response in Chinese patients

AIM

This study examined whether the ABCG2 421C>A polymorphism and variants in other genes potentially related to the pharmacokinetics of rosuvastatin influenced the plasma concentration of rosuvastatin in Chinese patients with hypercholesterolemia.

PATIENTS & METHODS

Overnight fasting blood samples were collected from 291 patients who had received a rosuvastatin 10 mg night-time dose for at least 4 weeks. Plasma concentrations of rosuvastatin and N-desmethyl rosuvastatin were quantified using liquid chromatography tandem mass spectrometry.

RESULTS

In subjects with the ABCG2 421AA genotype (n = 39), the mean plasma concentrations of rosuvastatin and its metabolite were 63 and 41% greater than the values in those with the 421CA genotype (n = 108) and 120 and 99% greater than in those with the 421CC genotype (n = 129). The plasma concentrations of rosuvastatin were associated (r = -0.194; p = 0.001) with the percentage reduction in low-density lipoprotein cholesterol with rosuvastatin, but the association was not significant after adjusting for the ABCG2 421C>A polymorphism. The SLCO1B1 521T>C polymorphism was associated with increased plasma concentrations of rosuvastatin and impaired N-demethylation of rosuvastatin, but had no impact on its lipid-lowering effect. Polymorphisms in CYP2C9, CYP2C19 and SLC10A1 had minimal effects.

CONCLUSION

These findings suggest that the increased plasma concentrations of rosuvastatin in Chinese patients are associated with increased lipid-lowering effects and lower doses of rosuvastatin should be effective in subjects with the ABCG2 421C>A variant.

In silico prediction of inhibition of promiscuous breast cancer resistance protein (BCRP/ABCG2)

BACKGROUND

Breast cancer resistant protein has an essential role in active transport of endogenous substances and xenobiotics across extracellular and intracellular membranes along with P-glycoprotein. It also plays a major role in multiple drug resistance and permeation of blood-brain barrier. Therefore, it is of great importance to derive theoretical models to predict the inhibition of both transporters in the process of drug discovery and development. Hitherto, very limited BCRP inhibition predictive models have been proposed as compared with its P-gp counterpart.

METHODOLOGY/PRINCIPAL FINDINGS

An in silico BCRP inhibition model was developed in this study using the pharmacophore ensemble/support vector machine scheme to take into account the promiscuous nature of BCRP. The predictions by the PhE/SVM model were found to be in good agreement with the observed values for those molecules in the training set (n= 22, r2 =0.82, qCV2=0.73, RMSE= 0.40, s = 0.24), test set (n =97, q2=0.75-0.89, RMSE= 0.31, s= 0.21), and outlier set (n= 16, q2 =0.72-0.91, RMSE= 0.29, s=0.17). When subjected to a variety of statistical validations, the developed PhE/SVM model consistently met the most stringent criteria. A mock test by HIV protease inhibitors also asserted its predictivity.

CONCLUSIONS/SIGNIFICANCE

It was found that this accurate, fast, and robust PhE/SVM model can be employed to predict the BCRP inhibition of structurally diverse molecules that otherwise cannot be carried out by any other methods in a high-throughput fashion to design therapeutic agents with insignificant drug toxicity and unfavorable drug-drug interactions mediated by BCRP to enhance clinical efficacy and/or circumvent drug resistance.

Association between statin-induced creatine kinase elevation and genetic polymorphisms in SLCO1B1, ABCB1 and ABCG2

PURPOSE

Treatment with statins requires close monitoring of serum creatine kinase (CK) levels to prevent myopathy, a common and potentially serious dose-dependent adverse effect of these drugs. We have investigated the correlation between elevated CK levels and polymorphisms in the genes encoding transporters involved in statin disposition.

METHODS

Patients with and without statin-induced elevated serum CK levels were genotyped for polymorphisms in SLCO1B1 (SLCO1B1 A388G and SLCO1B1 T521C), ABCB1 (ABCB1 C1236T and ABCB1 C3435T) and ABCG2 (ABCG2 C421A).

RESULTS

Patients carrying SLCO1B1 T521C or ABCB1 C1236T single nucleotide polymorphisms (SNPs) had an odds ratio (OR) for statin-induced elevated serum CK levels of 8.86 (p<0.01) and 4.67 (p<0.05), respectively, while patients carrying the SLCO1B1 A388G SNP had an OR of 0.24 (p<0.05). An arbitrary score based on genotype combination discriminated patients with and without CK elevation at a specificity of 97 % and a sensitivity of 39 %.

CONCLUSION

Genotyping of the SLCO1B1, ABCB1 and ABCG2 genes deserves consideration as a clinical approach to improve statin safety while concomitantly reducing the burden of blood tests for CK measurements.

The pharmacogenomics of statins

The statin class of cholesterol-lowering drugs have been used for decades to successfully lower plasma cholesterol concentrations and cardiovascular risk. Adverse effects of statins are generally considered mild, but increase with age of patients and polypharmacy. One aspect of statin therapy that is still difficult for prescribers to predict is the individual's response to statin therapy. Recent advances in the field of pharmacogenomics have indicated variants of candidate genes that affect statin efficacy and safety. In this review, a number of candidates that affect statin pharmacokinetics and pharmacodynamics are discussed. Some of these candidates, in particular those involved in import and efflux of statins, have now been linked to increased risk of side effects. Furthermore, pharmacogenomic studies continue to reveal new players that are involved in the fine-tuning of the complex regulation of cholesterol homeostasis and response to statins.

Managing hypercholesterolemia and preventing cardiovascular events in elderly and younger Chinese adults: focus on rosuvastatin

Coronary heart disease (CHD) is the leading cause of death worldwide. The efficacy and safety of statins in primary and secondary prevention of CHD is confirmed in several large studies, and rosuvastatin is the latest statin on market. We review the published literature on rosuvastatin in Chinese people. The pharmacokinetics of rosuvastatin in Chinese is somewhat different from that in Caucasians, but this does not influence the linear relationship between dosage and efficacy and with no drug accumulation. Rosuvastatin 5–20 mg/day is effective and safe in decreasing low-density lipoprotein cholesterol in both younger and elderly patients with hypercholesterolemia, even in very elderly patients. Rosuvastatin also shows anti-inflammatory and antiatherosclerosis features, such as reducing carotid intima-media thickness and plaque area. Rosuvastatin can also improve the prognosis of Chinese CHD patients, such as in the case of acute myocardial infarction. Its adverse-event rate is low and comparable to other statins. In conclusion, rosuvastatin is effective and safe for younger or elderly Chinese patients.

Clinical impact of genetic variants of drug transporters in different ethnic groups within and across regions

Drug transporters, together with drug metabolic enzymes, are major determinants of drug disposition and are known to alter the response to many commonly used drugs. Substantial frequency differences for known variants exist across geographic regions for certain drug transporters. To deliver efficacious medicine with the right dose for each patient, it is important to understand the contribution of genetic variants for drug transporters. Recently, mutual pharmacokinetic data usage among Asian regions, which are thought to be relatively similar in their own genetic background, is expected to accelerate new drug applications and reduce developmental costs. Polymorphisms of drug transporters could be key factors to be considered in implementing multiethnic global clinical trials. This review addresses the current knowledge on genetic variations of major drug transporters affecting drug disposition, efficacy and toxicity, focusing on the east Asian populations, and provides insights into future directions for precision medicine and drug development in east Asia.

Evaluation of the pharmacokinetics and drug interactions of the two recently developed statins, rosuvastatin and pitavastatin

INTRODUCTION

Statins are the cornerstone of lipid-lowering therapy to reduce the risk of coronary heart disease. Rosuvastatin and pitavastatin are the two recently developed statins with less potential for drug interaction resulting in improved safety profiles.

AREAS COVERED

This review summarizes the pharmacokinetics and drug interactions of rosuvastatin and pitavastatin. The materials reviewed were identified by searching PubMed for publications using 'rosuvastatin', 'pitavastatin', 'statins', 'pharmacokinetics' and 'drug interaction' as the search terms.

EXPERT OPINION

Rosuvastatin and pitavastatin have favorable pharmacokinetic and safety profiles as their disposition does not depend on or is only marginally influenced by cytochrome P450 (CYP) enzymes, thus potentially reducing the risk of drug-drug interactions of these two statins with other drugs known to inhibit CYP enzymes. However, drug transporters play a significant role in the disposition of rosuvastatin and pitavastatin and drug interactions may occur through these. Genetic polymorphisms in drug transporters may also affect the pharmacokinetics, drug interactions and/or the lipid-lowering effect of these statins to a different extent.

Interindividual variability in hepatic organic anion-transporting polypeptides and P-glycoprotein (ABCB1) protein expression: quantification by liquid chromatography tandem mass spectroscopy and influence of genotype, age, and sex

Interindividual variability in protein expression of organic anion-transporting polypeptides (OATPs) OATP1B1, OATP1B3, OATP2B1, and multidrug resistance-linked P-glycoprotein (P-gp) or ABCB1 was quantified in frozen human livers (n = 64) and cryopreserved human hepatocytes (n = 12) by a validated liquid chromatography tandem mass spectroscopy (LC-MS/MS) method. Membrane isolation, sample workup, and LC-MS/MS analyses were as described before by our laboratory. Briefly, total native membrane proteins, isolated from the liver tissue and cryopreserved hepatocytes, were trypsin digested and quantified by LC-MS/MS using signature peptide(s) unique to each transporter. The mean ± S.D. (maximum/minimum range in parentheses) protein expression (fmol/µg of membrane protein) in human liver tissue was OATP1B1- 2.0 ± 0.9 (7), OATP1B3- 1.1 ± 0.5 (8), OATP2B1- 1 1.7 ± 0.6 (5), and P-gp- 0.4 ± 0.2 (8). Transporter expression in the liver tissue was comparable to that in the cryopreserved hepatocytes. Most important is that livers with SLCO1B1 (encoding OATP1B1) haplotypes *14/*14 and *14/*1a [i.e., representing single nucleotide polymorphisms (SNPs), c.388A > G, and c.463C > A] had significantly higher (P < 0.0001) protein expression than the reference haplotype (*1a/*1a). Based on these genotype-dependent protein expression data, we predicted (using Simcyp) an up to ∼40% decrease in the mean area under the curve of rosuvastatin or repaglinide in subjects harboring these variant alleles compared with those harboring the reference alleles. SLCO1B3 (encoding OATP1B3) SNPs did not significantly affect protein expression. Age and sex were not associated with transporter protein expression. These data will facilitate the prediction of population-based human transporter-mediated drug disposition, drug-drug interactions, and interindividual variability through physiologically based pharmacokinetic modeling.

Hepatic basolateral efflux contributes significantly to rosuvastatin disposition II: characterization of hepatic elimination by basolateral, biliary, and metabolic clearance pathways in rat isolated perfused liver

Basolateral efflux clearance (CLBL) contributes significantly to rosuvastatin (RSV) elimination in sandwich-cultured hepatocytes (SCH). The contribution of CLBL to RSV hepatic elimination was determined in single-pass isolated perfused livers (IPLs) from wild-type (WT) and multidrug resistance-associated protein 2 (Mrp2)-deficient (TR(-)) rats in the absence and presence of the P-glycoprotein and breast cancer resistance protein (Bcrp) inhibitor, elacridar (GF120918); clearance values were compared with SCH. RSV biliary clearance (CLBile) was ablated almost completely by GF120918 in TR(-) IPLs, confirming that Mrp2 and Bcrp primarily are responsible for RSV CLBile. RSV appearance in outflow perfusate was attributed primarily to CLBL, which was impaired in TR(-) IPLs. CLBL was ≈ 6-fold greater than CLBile in the linear range in WT IPLs in the absence of GF120918. Recovery of unchanged RSV in liver tissue increased in TR(-) compared with WT (≈ 25 versus 6% of the administered dose) due to impaired CLBL and CLBile. RSV pentanoic acid, identified by high-resolution liquid chromatography-tandem mass spectroscopy, comprised ≈ 40% of total liver content and ≈ 16% of the administered dose in TR(-) livers at the end of perfusion, compared with ≈ 30 and 3% in WT livers, consistent with impaired RSV excretion and "shunting" to the metabolic pathway. In vitro-ex vivo extrapolation between WT SCH and IPLs (without GF120918) revealed that uptake clearance and CLBL were 4.2- and 6.4-fold lower, respectively, in rat SCH compared with IPLs; CLBile translated almost directly (1.1-fold). The present IPL data confirmed the significant role of CLBL in RSV hepatic elimination, and demonstrated that both CLBL and CLBile influence RSV hepatic and systemic exposure.

Hepatic basolateral efflux contributes significantly to rosuvastatin disposition I: characterization of basolateral versus biliary clearance using a novel protocol in sandwich-cultured hepatocytes

Transporters responsible for hepatic uptake and biliary clearance (CLBile) of rosuvastatin (RSV) have been well characterized. However, the contribution of basolateral efflux clearance (CLBL) to hepatic and systemic exposure of RSV is unknown. Additionally, the appropriate design of in vitro hepatocyte efflux experiments to estimate CLBile versus CLBL remains to be established. A novel uptake and efflux protocol was developed in sandwich-cultured hepatocytes (SCH) to achieve desired tight junction modulation while maintaining cell viability. Subsequently, studies were conducted to determine the role of CLBL in the hepatic disposition of RSV using SCH from wild-type (WT) and multidrug resistance-associated protein 2 (Mrp2)-deficient (TR(-)) rats in the absence and presence of the P-glycoprotein and breast cancer resistance protein (Bcrp) inhibitor elacridar (GF120918). RSV CLBile was nearly ablated by GF120918 in TR(-) SCH, confirming that Mrp2 and Bcrp are responsible for the majority of RSV CLBile. Pharmacokinetic modeling revealed that CLBL and CLBile represent alternative elimination routes with quantitatively similar contributions to the overall hepatocellular excretion of RSV in rat SCH under baseline conditions (WT SCH in the absence of GF120918) and also in human SCH. Membrane vesicle experiments revealed that RSV is a substrate of MRP4 (Km = 21 ± 7 µM, Vmax = 1140 ± 210 pmol/min per milligram of protein). Alterations in MRP4-mediated RSV CLBL due to drug-drug interactions, genetic polymorphisms, or disease states may lead to changes in hepatic and systemic exposure of RSV, with implications for the safety and efficacy of this commonly used medication.

Clinical and pharmacogenetic predictors of circulating atorvastatin and rosuvastatin concentrations in routine clinical care

BACKGROUND

A barrier to statin therapy is myopathy associated with elevated systemic drug exposure. Our objective was to examine the association between clinical and pharmacogenetic variables and statin concentrations in patients.

METHODS AND RESULTS

In total, 299 patients taking atorvastatin or rosuvastatin were prospectively recruited at an outpatient referral center. The contribution of clinical variables and transporter gene polymorphisms to statin concentration was assessed using multiple linear regression. We observed 45-fold variation in statin concentration among patients taking the same dose. After adjustment for sex, age, body mass index, ethnicity, dose, and time from last dose, SLCO1B1 c.521T>C (P<0.001) and ABCG2 c.421C>A (P<0.01) were important to rosuvastatin concentration (adjusted R(2)=0.56 for the final model). Atorvastatin concentration was associated with SLCO1B1 c.388A>G (P<0.01) and c.521T>C (P<0.05) and 4β-hydroxycholesterol, a CYP3A activity marker (adjusted R(2)=0.47). A second cohort of 579 patients from primary and specialty care databases were retrospectively genotyped. In this cohort, genotypes associated with statin concentration were not differently distributed among dosing groups, implying providers had not yet optimized each patient's risk-benefit ratio. Nearly 50% of patients in routine practice taking the highest doses were predicted to have statin concentrations greater than the 90th percentile.

CONCLUSIONS

Interindividual variability in statin exposure in patients is associated with uptake and efflux transporter polymorphisms. An algorithm incorporating genomic and clinical variables to avoid high atorvastatin and rosuvastatin levels is described; further study will determine whether this approach reduces incidence of statin myopathy.

Pharmacogenomics of lipid-lowering therapies

Statins are the most widely used group of lipid-lowering drugs and they have been shown to be effective in the prevention of cardiovascular disease, primarily by reducing plasma low-density lipoprotein cholesterol concentrations and possibly through other pleiotropic effects. However, there are large variations in lipid responses to statins and some patients have intolerable muscle adverse drug reactions, which may in part be related to genetic factors. In the last decade, pharmacogenetic studies on statins ranging from the candidate gene approach to the more recent genome-wide association studies have provided evidence that genetic variations play an important role in determining statin responses. This review summarizes the current understanding on the pharmacogenomics of statins and other lipid-lowering drugs in current use.

Pharmacogenetics and cardiovascular disease--implications for personalized medicine

The past decade has seen tremendous advances in our understanding of the genetic factors influencing response to a variety of drugs, including those targeted at treatment of cardiovascular diseases. In the case of clopidogrel, warfarin, and statins, the literature has become sufficiently strong that guidelines are now available describing the use of genetic information to guide treatment with these therapies, and some health centers are using this information in the care of their patients. There are many challenges in moving from research data to translation to practice; we discuss some of these barriers and the approaches some health systems are taking to overcome them. The body of literature that has led to the clinical implementation of CYP2C19 genotyping for clopidogrel, VKORC1, CYP2C9; and CYP4F2 for warfarin; and SLCO1B1 for statins is comprehensively described. We also provide clarity for other genes that have been extensively studied relative to these drugs, but for which the data are conflicting. Finally, we comment briefly on pharmacogenetics of other cardiovascular drugs and highlight β-blockers as the drug class with strong data that has not yet seen clinical implementation. It is anticipated that genetic information will increasingly be available on patients, and it is important to identify those examples where the evidence is sufficiently robust and predictive to use genetic information to guide clinical decisions. The review herein provides several examples of the accumulation of evidence and eventual clinical translation in cardiovascular pharmacogenetics.

Drug-drug interaction studies: regulatory guidance and an industry perspective

Recently, the US Food and Drug Administration and European Medicines Agency have issued new guidance for industry on drug interaction studies, which outline comprehensive recommendations on a broad range of in vitro and in vivo studies to evaluate drug-drug interaction (DDI) potential. This paper aims to provide an overview of these new recommendations and an in-depth scientifically based perspective on issues surrounding some of the recommended approaches in emerging areas, particularly, transporters and complex DDIs. We present a number of theoretical considerations and several case examples to demonstrate complexities in applying (1) the proposed transporter decision trees and associated criteria for studying a broad spectrum of transporters to derive actionable information and (2) the recommended model-based approaches at an early stage of drug development to prospectively predict DDIs involving time-dependent inhibition and mixed inhibition/induction of drug metabolizing enzymes. We hope to convey the need for conducting DDI studies on a case-by-case basis using a holistic scientifically based interrogative approach and to communicate the need for additional research to fill in knowledge gaps in these areas where the science is rapidly evolving to better ensure the safety and efficacy of new therapeutic agents.

Effect of the ATP-binding cassette transporter ABCG2 on pharmacokinetics: experimental findings and clinical implications

INTRODUCTION

The ATP-binding cassette transporter ABCG2 can actively extrude a broad range of endogenous and exogenous substrates across biological membranes. Thereby, ABCG2 limits oral drug bioavailability, mediates hepatobiliary and renal excretion and participates functionally in the blood-brain barrier.

AREAS COVERED

The paper provides a review of the clinical evidence of the role of ABCG2 in the bioavailability and brain disposition of drugs. It also sheds light on the value of experimental/preclinical data in predicting the role of ABCG2 in pharmacokinetics in humans.

EXPERT OPINION

Experimental studies indicate that ABCG2 may limit the oral bioavailability and brain penetration of many drugs. ABCG2 has also been recognized as an important determinant of the disposition of some drugs in humans. For example, loss-of-function variants of ABCG2 affect the pharmacokinetics and pharmacodynamics of rosuvastatin in a clinically significant manner. Moreover, clinically relevant pharmacokinetic drug-drug interactions have been attributed to ABCG2 inhibition. However, examples from human studies are still rare compared with the overwhelming evidence from experimental studies. The large degree of functional redundancy of ABCG2 with other transporters such as P-glycoprotein may explain the rare occurrence of ABCG2-dependent drug-drug interactions in humans. Providing clinicians with consolidated information on the clinically relevant interactions of drugs with ABCG2 remains a matter of future exploration.

Interindividual variability in the hepatic expression of the human breast cancer resistance protein (BCRP/ABCG2): effect of age, sex, and genotype

Breast cancer resistance protein (BCRP), an efflux transporter expressed at the bile canalicular membrane, is responsible for the biliary clearance of many drugs. Data on the interindividual variability of hepatic BCRP expression are needed for in vitro to in vivo extrapolation of the biliary clearance of a BCRP substrate drug. Therefore, we measured the expression of BCRP in human livers (n = 65) by liquid chromatography coupled with tandem mass spectrometry. A calibration curve was generated using a synthetic signature peptide (SSLLDVLAAR) as the calibrator and the corresponding synthetic stable isotope-labeled peptide as the internal standard. The analytical method was accurate and precise. BCRP expression in 50 livers, where it was measurable, was 137.9 ± 42.1 atmol/µg of membrane protein (range 69.7-246.4 atmol/µg of membrane protein). BCRP expression was not associated with age (7-70 years), sex, or mRNA expression. BCRP expression in livers with the variant C421A (rs2231142) allele (14 heterozygotes, two homozygotes; among these, eight livers were below lower limit of quantification) was significantly lower than that in the wild-type livers (p < 0.002). Integration of these data with data on the hepatic expression of other transporters will allow refinement of physiologically based pharmacokinetic models to predict the pharmacokinetics, hepatic exposure, and drug-drug interactions of drugs (and/or their metabolites).

Individualized risk for statin-induced myopathy: current knowledge, emerging challenges and potential solutions

Skeletal muscle toxicity is the primary adverse effect of statins. In this review, we summarize current knowledge regarding the genetic and nongenetic determinants of risk for statin induced myopathy. Many genetic factors were initially identified through candidate gene association studies limited to pharmacokinetic (PK) targets. Through genome-wide association studies, it has become clear that SLCO1B1 is among the strongest PK predictors of myopathy risk. Genome-wide association studies have also expanded our understanding of pharmacodynamic candidate genes, including RYR2. It is anticipated that deep resequencing efforts will define new loci with rare variants that also contribute, and sophisticated computational approaches will be needed to characterize gene-gene and gene-environment interactions. Beyond environment, race is a critical covariate, and its influence is only partly explained by geographic differences in the frequency of known pharmacodynamic and PK variants. As such, admixture analyses will be essential for a full understanding of statin-induced myopathy.

Impact of common genetic variation on response to simvastatin therapy among 18 705 participants in the Heart Protection Study

Aims

Statins reduce LDL cholesterol (LDL-C) and the risk of vascular events, but it remains uncertain whether there is clinically relevant genetic variation in their efficacy. This study of 18 705 individuals aims to identify genetic variants related to the lipid response to simvastatin and assess their impact on vascular risk response.

Methods and results

A genome-wide study of the LDL-C and apolipoprotein B (ApoB) response to 40 mg simvastatin daily was performed in 3895 participants in the Heart Protection Study, and the nine strongest associations were tested in 14 810 additional participants. Selected candidate genes were also tested in up to 18 705 individuals. There was 90% power to detect differences of 2.5% in LDL-C response (e.g. 42.5 vs. 40% reduction) in the genome-wide study and of 1% in the candidate gene study. None of the associations from the genome-wide study was replicated, and nor were significant associations found for 26 of 36 candidates tested. Novel lipid response associations with variants in LPA, CELSR2/PSRC1/SORT1, and ABCC2 were found, as well as confirmatory evidence for published associations in LPA, APOE, and SLCO1B1. The largest and most significant effects were with LPA and APOE, but were only 2–3% per allele. Reductions in the risk of major vascular events during 5 years of statin therapy among 18 705 high-risk patients did not differ significantly across genotypes associated with the lipid response.

Conclusions

Common genetic variants do not appear to alter the lipid response to statin therapy by more than a few per cent, and there were similar large reductions in vascular risk with simvastatin irrespective of genotypes associated with the lipid response to simvastatin. Consequently, their value for informing clinical decisions related to maximizing statin efficacy appears to be limited.

Clinical response to statins: mechanism(s) of variable activity and adverse effects

Statins represent a major advance in the treatment of hypercholesterolemia, a significant risk factor for atherosclerosis. There is, however, notable interindividual variation in the cholesterolemic response to statins, and the origin of this variability is poorly understood; pharmacogenetics has attempted to determine the role of genetic factors. Myopathy, further, has been reported in a considerable percentage of patients, but the mechanisms underlying muscle injury have yet to be fully characterized. Most statins are the substrates of several cytochrome P450s (CYP). CYP polymorphisms may be responsible for variations in hypolipidemic activity; inhibitors of CYPs, e.g. of CYP3A4, can significantly raise plasma concentrations of several statins, but consequences in terms of clinical efficacy are not uniform. Pravastatin and rosuvastatin are not susceptible to CYP inhibition but are substrates of the organic anion-transporting polypeptide (OATP) 1B1, encoded by the SLCO1B1 gene. Essentially all statins are, in fact, substrates of membrane transporters: SLCO1B1 polymorphisms can decrease the liver uptake, as well as the therapeutic potential of these agents, and may be linked to their muscular side-effects. A better understanding of the mechanisms of statin handling will help to minimize adverse effects and interactions, as well as to improve their lipid-lowering efficiency.

Problems with the collection and interpretation of Asian-American health data: omission, aggregation, and extrapolation

Asian-American citizens are the fastest growing racial/ethnic group in the United States. Nevertheless, data on Asian American health are scarce, and many health disparities for this population remain unknown. Much of our knowledge of Asian American health has been determined by studies in which investigators have either grouped Asian-American subjects together or examined one subgroup alone (e.g., Asian Indian, Chinese, Filipino, Japanese, Korean, Vietnamese). National health surveys that collect information on Asian-American race/ethnicity frequently omit this population in research reports. When national health data are reported for Asian-American subjects, it is often reported for the aggregated group. This aggregation may mask differences between Asian-American subgroups. When health data are reported by Asian American subgroup, it is generally reported for one subgroup alone. In the Ni-Hon-San study, investigators examined cardiovascular disease in Japanese men living in Japan (Nippon; Ni), Honolulu, Hawaii (Hon), and San Francisco, CA (San). The findings from this study are often incorrectly extrapolated to other Asian-American subgroups. Recommendations to correct the errors associated with omission, aggregation, and extrapolation include: oversampling of Asian Americans, collection and reporting of race/ethnicity data by Asian-American subgroup, and acknowledgement of significant heterogeneity among Asian American subgroups when interpreting data.

The farnesoid X receptor -1G>T polymorphism influences the lipid response to rosuvastatin

The bile acid-activated nuclear receptor farnesoid X receptor (FXR) plays an important role in lipid and glucose metabolism, and in addition, it regulates multiple drug transporters involved in statin disposition. We examined whether a functional single nucleotide polymorphism (SNP) in FXR (-1G>T) influenced the lipid-lowering effect of rosuvastatin. In 385 Chinese patients with hyperlipidemia who had been treated with rosuvastatin 10 mg daily for at least 4 weeks, the association between the FXR -1G>T SNP and lipid response to rosuvastatin was analyzed. The FXR -1G>T SNP was not associated with baseline lipids but was significantly associated with the LDL cholesterol (LDL-C) and total cholesterol response to rosuvastatin. Carriers of the T-variant allele (GT+TT = 68+3) had 4.4% (95% CI: 1.2, 7.5%, P = 0.006) and 2.6% (95% CI: 0.3, 5.0%; P < 0.05) greater reductions in LDL-C and total cholesterol, respectively, compared with those with homozygous wild-type alleles. The association between the FXR polymorphism and the LDL-C response to rosuvastatin remained significant after adjusting for other covariants. This association of the variant allele of the FXR -1G>T polymorphism with a greater LDL-C response to rosuvastatin may suggest that this polymorphism influences the expression of the hepatic efflux transporters involved in biliary excretion of rosuvastatin.

Statin dose in Asians: is pharmacogenetics relevant?

Historically the efficacy and safety of statins has mostly been studied in western populations. Few such studies have been carried out in Asians until recent years. These studies revealed interesting similarities and differences for statin use between Asians and Caucasians. One clinically important question subsequently raised is whether Asians need lower statin doses compared with Caucasians. Many practicing physicians believe that statin doses are lower in Asians because of the generally lower bodyweight and BMI. Whether this belief is based on sound scientific evidence needs to be reviewed. Furthermore, since the decision of optimal dose is based on both efficacy and safety, both of which may be impacted by genetic factors, one may ask whether pharmacogenetics plays a role in the dose difference, if such a difference exists. There is a clinical need to critically and comprehensively article the literature to answer these questions, and summarize future directions of research in the field. This article serves the above purpose.

Eltrombopag increases plasma rosuvastatin exposure in healthy volunteers

WHAT IS ALREADY KNOWN ABOUT THIS SUBJECT

OATP1B1 is important for hepatic uptake of rosuvastatin and BCRP is important for rosuvastatin absorption and elimination. Eltrombopag inhibits OATP1B1 and BCRP in vitro at clinically relevant concentrations. Inhibition of these transporters could change cholesterol-lowering efficacy and increase the risk of exposure-dependent toxicities. To determine if co-administration of eltrombopag with rosuvastatin alters plasma rosuvastatin exposure, an open-label study was conducted in 42 healthy adult subjects.

WHAT THIS STUDY ADDS

Concomitant administration of eltrombopag with rosuvastatin was associated with increased rosuvastatin exposure via inhibition of drug transporters. The therapeutic index of HMG Co-A reductase inhibitors may be reduced by the concomitant use of eltrombopag. In subjects taking eltrombopag, a reduced dose of HMG Co-A reductase inhibitors may be needed.

AIM

Eltrombopag, an oral, nonpeptide thrombopoietin receptor agonist, inhibits the organic anion transporting polypeptide 1B1 (OATP1B1) and breast cancer resistance protein (BCRP) in vitro. OATP1B1 is important for hepatic uptake of rosuvastatin and inhibition of this transporter could reduce cholesterol-lowering efficacy and increase the risk of exposure-dependent toxicities. In contrast, BCRP is an efflux transporter and inhibition of this transporter could increase both hepatic and plasma rosuvastatin concentrations, resulting in increased efficacy and toxicity. To determine if co-administration of eltrombopag with rosuvastatin alters plasma rosuvastatin exposure, an open-label study was conducted in 42 healthy adult subjects.

METHODS

Subjects received rosuvastatin and eltrombopag orally: day 1, rosuvastatin 10 mg single dose; days 6 to 9, eltrombopag 75 mg once daily; day 10, eltrombopag 75 mg once daily and rosuvastatin 10 mg single dose. Adverse event assessments were performed daily and at the follow-up visit. Plasma samples for pharmacokinetic analysis were collected days 1 to 5 and days 10 to 14.

RESULTS

Co-administration of eltrombopag with rosuvastatin increased geometric mean (90% confidence interval) plasma rosuvastatin AUC(0,∞) by 55% (42%, 69%) and C(max) by 103% (82%, 126%) in the overall study population, with a larger interaction in the non-Asian compared with Asian subjects.

CONCLUSIONS

Concomitant administration of eltrombopag with rosuvastatin was associated with increased rosuvastatin exposure. The therapeutic index of HMG Co-A reductase inhibitors may be reduced by the concomitant use of eltrombopag. In subjects taking eltrombopag, a reduced dose of HMG Co-A reductase inhibitors may be needed.

Functional significance of genetic polymorphisms in P-glycoprotein (MDR1, ABCB1) and breast cancer resistance protein (BCRP, ABCG2)

Recent pharmacogenomic/pharmacogenetic (PGx) studies have disclosed important roles for drug transporters in the human body. Changes in the functions of drug transporters due to drug/food interactions or genetic polymorphisms, for example, are associated with large changes in pharmacokinetic (PK) profiles of substrate drugs, leading to changes in drug response and side effects. This information is extremely useful not only for drug development but also for individualized treatment. Among drug transporters, the ATP-binding cassette (ABC) transporters are expressed in most tissues in humans, and play protective roles; reducing drug absorption from the gastrointestinal tract, enhancing drug elimination into bile and urine, and impeding the entry of drugs into the central nervous system and placenta. In addition to PK/pharmacodynamic (PD) issues, ABC transporters are reported as etiologic and prognostic factors (or biomarkers) for genetic disorders. Although a consensus has not yet been reached, clinical studies have demonstrated that the PGx of ABC transporters influences the overall outcome of pharmacotherapy and contributes to the pathogenesis and progression of certain disorders. This review explains the impact of PGx in ABC transporters in terms of PK/PD, focusing on P-glycoprotein and breast cancer resistance protein (BCRP).

Diabetic dyslipidaemia in Asian populations in the Western Pacific Region: what we know and don't know

Approximately 77 million persons with diabetes reside in the Western Pacific Region. This number is estimated to rise to 113 million in 2030 with increasing burden of cardio-renal disease, affecting an increasingly young population. Randomized clinical trials have confirmed the benefits of using statins to reduce low-density lipoprotein cholesterol in preventing cardiovascular disease (CVD) in Caucasians, although similar data are lacking in Asia. Experts from the Western Pacific Region met and reviewed evidence regarding risk association of diabetic dyslipidaemia with cardio-renal disease, effects of lipid lowering, recommended guidelines and clinical practices in Asian populations. There is strong evidence supporting the role of diabetic dyslipidaemia in cardio-renal disease and the benefits of lipid lowering in these populations. The high rate of diabetic kidney disease, its close links with CVD, and the benefits of lipid lowering on renal function are particularly relevant to this population. While most national guidelines use criteria similar to the West in management of diabetic dyslipidaemia, there are consistently low rates of use of lipid-lowering drugs and attaining treatment goals in the region. The group recommends conducting randomized studies, strengthening of the health care system to promote early detection, and intervention of diabetic dyslipidaemia to prevent end organ damage.

Drug transporters in drug efficacy and toxicity

Drug transporters are now widely acknowledged as important determinants governing drug absorption, excretion, and, in many cases, extent of drug entry into target organs. There is also a greater appreciation that altered drug transporter function, whether due to genetic polymorphisms, drug-drug interactions, or environmental factors such as dietary constituents, can result in unexpected toxicity. Such effects are in part due to the interplay between various uptake and efflux transporters with overlapping functional capabilities that can manifest as marked interindividual variability in drug disposition in vivo. Here we review transporters of the solute carrier (SLC) and ATP-binding cassette (ABC) superfamilies considered to be of major importance in drug therapy and outline how understanding the expression, function, and genetic variation in such drug transporters will result in better strategies for optimal drug design and tissue targeting as well as reduce the risk for drug-drug interactions and adverse drug responses.

Rabdomiólise após exercício físico não intenso

Discutiremos um raro caso clínico de rabdomiólise ocorrido após um exercício físico habitual e não intenso, em paciente masculino de 34 anos e os prováveis fatores desencadeantes envolvidos, bem como suas implicações clínicas. Destacando-se a elevação expressiva e não vista em outros trabalhos como da creatinoquinase, enzimas hepáticas, e as medidas clínicas adotadas para a prevenção de complicações renais sérias e com risco grave para o paciente em análise.

Pharmacogenetic analysis of lipid responses to rosuvastatin in Chinese patients

Lipid changes with statin treatments vary greatly between individuals for reasons which are largely unknown. This study was performed to examine the genetic determinants of lipid responses to rosuvastatin in Chinese patients. A total of 125 polymorphisms in 61 candidate genes from 386 Chinese patients were analyzed for association with the lipid responses to rosuvastatin 10 mg daily. The polymorphisms most highly associated with the low-density lipoprotein cholesterol (LDL-C) response were 421C>A in the ATP-binding cassette G2 gene (P=9.2×10), followed by 18281G>A (V257M) in the flavin-containing monooxygenase 3 gene (P=0.0002), 1421C>G in the lipoprotein lipase gene (P=0.002), and rs4420638 in the apolipoprotein E/C-I/C-IV/C-II gene cluster (P=0.004). Patients with familial hypercholesterolemia had 2.6% smaller reductions in LDL-C compared with patients without familial hypercholesterolemia. This study identified some genetic determinants of LDL-C response to rosuvastatin in Chinese patients, which need to be replicated in other populations.