OATP1B1 388A>G polymorphism and pharmacokinetics of pitavastatin in Chinese healthy volunteers

Physiologically based pharmacokinetic (PBPK) modeling of pitavastatin in relation to SLCO1B1 genetic polymorphism

Pitavastatin, a potent 3-hydroxymethylglutaryl coenzyme A reductase inhibitor, is indicated for the treatment of hypercholesterolemia and mixed dyslipidemia. Hepatic uptake of pitavastatin is predominantly occupied by the organic anion transporting polypeptide 1B1 (OATP1B1) and solute carrier organic anion transporter family member 1B1 (SLCO1B1) gene, which is a polymorphic gene that encodes OATP1B1. SLCO1B1 genetic polymorphism significantly alters the pharmacokinetics of pitavastatin. This study aimed to establish the physiologically based pharmacokinetic (PBPK) model to predict pitavastatin pharmacokinetics according to SLCO1B1 genetic polymorphism. PK-Sim® version 10.0 was used to establish the whole-body PBPK model of pitavastatin. Our pharmacogenomic data and a total of 27 clinical pharmacokinetic data with different dose administration and demographic properties were used to develop and validate the model, respectively. Physicochemical properties and disposition characteristics of pitavastatin were acquired from previously reported data or optimized to capture the plasma concentration-time profiles in different SLCO1B1 diplotypes. Model evaluation was performed by comparing the predicted pharmacokinetic parameters and profiles to the observed data. Predicted plasma concentration-time profiles were visually similar to the observed profiles in the non-genotyped populations and different SLCO1B1 diplotypes. All fold error values for AUC and Cmax were included in the two fold range of observed values. Thus, the PBPK model of pitavastatin in different SLCO1B1 diplotypes was properly established. The present study can be useful to individualize the dose administration strategy of pitavastatin in individuals with various ages, races, and SLCO1B1 diplotypes.

A gene risk score using missense variants in SLCO1B1 is associated with earlier onset statin intolerance

BACKGROUND AND AIMS

The efficacy of statin therapy is hindered by intolerance to the therapy, leading to discontinuation. Variants in SLCO1B1, which encodes the hepatic transporter OATB1B1, influence statin pharmacokinetics, resulting in altered plasma concentrations of the drug and its metabolites. Current pharmacogenetic guidelines require sequencing of the SLCO1B1 gene, which is more expensive and less accessible than genotyping. In this study, we aimed to develop an easy, clinically implementable functional gene risk score (GRS) of common variants in SLCO1B1 to identify patients at risk of statin intolerance.

METHODS AND RESULTS

A GRS was developed from four common variants in SLCO1B1. In statin users from Tayside, Scotland, UK, those with a high-risk GRS had increased odds across three phenotypes of statin intolerance [general statin intolerance (GSI): ORGSI 2.42; 95% confidence interval (CI): 1.29-4.31, P = 0.003; statin-related myopathy: ORSRM 2.51; 95% CI: 1.28-4.53, P = 0.004; statin-related suspected rhabdomyolysis: ORSRSR 2.85; 95% CI: 1.03-6.65, P = 0.02]. In contrast, using the Val174Ala genotype alone or the recommended OATP1B1 functional phenotypes produced weaker and less reliable results. A meta-analysis with results from adjudicated cases of statin-induced myopathy in the PREDICTION-ADR Consortium confirmed these findings (ORVal174Ala 1.99; 95% CI: 1.01-3.95, P = 0.048; ORGRS 1.76; 95% CI: 1.16-2.69, P = 0.008). For those requiring high-dose statin therapy, the high-risk GRS was more consistently associated with the time to onset of statin intolerance amongst the three phenotypes compared with Val174Ala (GSI: HRVal174Ala 2.49; 95% CI: 1.09-5.68, P = 0.03; HRGRS 2.44; 95% CI: 1.46-4.08, P < 0.001). Finally, sequence kernel association testing confirmed that rare variants in SLCO1B1 are associated with the risk of intolerance (P = 0.02).

CONCLUSION

We provide evidence that a GRS based on four common SLCO1B1 variants provides an easily implemented genetic tool that is more reliable than the current recommended practice in estimating the risk and predicting early-onset statin intolerance.

Pharmacogenomics of lipid-lowering agents: the impact on efficacy and safety

Hyperlipidemia is a significant risk factor for cardiovascular disease morbidity and mortality. The lipid-lowering drugs are considered the cornerstone of primary and secondary prevention of atherosclerotic cardiovascular disease. Unfortunately, the lack of efficacy and associated adverse effects, ranging from mild-to-moderate to potentially life-threatening, lead to therapy discontinuation. Numerous reports support the role of gene polymorphisms in drugs' pharmacokinetic parameters and their associated adverse reactions. Therefore, this study aims to understand the pharmacogenomics of lipid-lowering drugs and the impact of genetic variants of key genes on the drugs' efficacy and toxicity. Indeed, genetically guided lipid-lowering therapy enhances overall safety, improves drug adherence and achieves long-term therapy.

Effects of SLCO1B1 and SLCO1B3 Genetic Polymorphisms on Valsartan Pharmacokinetics in Healthy Korean Volunteers

Purpose: This study aimed to examine OATP1B1 (SLCO1B1) and OATP1B3 (SLCO1B3) on the pharmacokinetics of valsartan. Twenty-five subjects were genotyped for 16 single-nucleotide polymorphisms of the SLCO1B1 and SLCO1B3 genes. Methods: After a single dose of 160 mg of valsartan was orally administered to healthy male volunteers, drug concentrations were assayed up to 48 h. The 25 subjects were genotyped for 16 single-nucleotide polymorphisms (SNPs) of the SLCO1B1 and SLCO1B3 genes. Subjects were classified into groups according to their SLCO1B1*1B haplotype; 23 subjects were carriers of SLCO1B1*1B and two subjects were included in the reference group with SLCO1B1*1A/*1A. Alternations of the splicing factor-binding site pattern caused by the given mutation were evaluated with the Human Splicing Finder (HSF) 3.1. Results: The subjects who carried SLCO1B1*1B showed a 2.3-fold higher clearance than those without the *1B haplotype. Mean C_max and AUC_inf were reduced by 45% and 54%, respectively, in the SLCO1B1*1B genotype group compared to the reference group with the *1A/*1A genotype (p < 0.01). The carriers of the rs4149153 T allele of SLCO1B3 had a 27% lower mean C_max and a 1.5-fold higher Vd compared to homozygotic CC carriers (p < 0.05). In a combined analysis of SLCO1B1 and SLCO1B3, subjects not carrying SLCO1B1 *1B and carrying SLCO1B3 rs4149153 T allele showed a 1.6-fold higher clearance than those with the other genotypes, whereas mean C_max and AUC_last were reduced by 35% and 42%, respectively (p < 0.05), in the subjects. HSF 3.1 analysis showed that rs4149153 could cause alterations of the acceptor splice site (TAAATACTAAAGAC to TAAATATTAAAGAC) with scoring change (from 72.57 to 71.92, difference = −0.9). Conclusion: It was found that plasma exposure to valsartan is significantly decreased in SLCO1B1*1B carriers and carriers of the rs4149153 T allele of SLCO1B3, possibly as a result of increased hepatic uptake.

Protocol for systematic review and meta-analysis: impact of statins as immune-modulatory agents on inflammatory markers in adults with chronic diseases

INTRODUCTION

Statins, also known as 3-hydroxy-3-methylglutaryl coenzyme-A (HMG-CoA) reductase inhibitors, are lipid-lowering agents that are central in preventing or reducing the complications of atherosclerotic cardiovascular disease. Because statins have anti-inflammatory properties, there is considerable interest in their therapeutic potential in other chronic inflammatory conditions. We aim to identify the statin with the greatest ability to reduce systemic inflammation, independent of the underlying disease entity.

METHODS AND ANALYSIS

We aim to conduct a comprehensive search of published and peer-reviewed randomised controlled clinical trials, with at least one intervention arm of a Food & Drug Administration-licensed or European Medicines Agency-licensed statin and a minimum treatment duration of 12 weeks. Our objective is to investigate the effect of statins (atorvastatin, fluvastatin, pitavastatin, pravastatin, rosuvastatin, simvastatin) on lipid profile, particularly, cholesterol low-density lipoprotein and inflammation markers such as high-sensitive C reactive protein (hsCRP), CRP, tumour necrosis factor alpha (TNF-α), interleukin-1β (IL-1β), IL-6, IL-8, soluble cluster of differentiation 14 (sCD14) or sCD16 in adults, published in the last 20 years (between January 1999 and December 2019). We aim to identify the most potent statin to reduce systemic inflammation and optimal dosing. The following databases will be searched: Medline, Scopus, Web of Science and Cochrane Library of Systematic Reviews. The risk of bias of included studies will be assessed by Cochrane Risk of Bias Tool and Quality Assessment Tool for Quantitative Studies. The quality of studies will be assessed, to show uncertainty, by the Jadad Score. If sufficient evidence is identified, a meta-analysis will be conducted with risk ratios or ORs with 95% CIs in addition to mean differences.

ETHICS AND DISSEMINATION

Ethics approval is not required as no primary data will be collected. Results will be presented at conferences and published in a peer-reviewed journal.

PROSPERO REGISTRATION NUMBER

CRD42020169919.

Interindividual and interethnic variability in drug disposition: polymorphisms in organic anion transporting polypeptide 1B1 (OATP1B1; SLCO1B1)

OATP1B1 (SLCO1B1) is predominantly expressed at the basolateral membrane of hepatocytes and is critically important for the hepatic uptake and clearance of numerous drug substrates and endogenous compounds. In general, the organic anion transporting polypeptides (OATP; SLCO) represent a superfamily of uptake transporters that mediate the sodium-independent transport of a diverse range of amphipathic organic compounds including bile salts, steroid conjugates, thyroid hormones, anionic peptides, numerous drugs and other xenobiotic substances. OATP1B1 is highly polymorphic and a number of relevant and ethnically dependent polymorphisms have been identified and functionally characterized. In particular, the SLCO1B1 521T>C and 388A>G polymorphisms are commonly occurring variants in ethnically diverse populations and numerous in vitro and clinical studies have evaluated the consequences of these variants to interindividual differences in drug disposition and response. OATP1B1 is particularly important for the disposition of HMG-CoA reductase inhibitors, or statins, as it is known to efficiently transport most statins to their site of action within hepatocytes. Many studies have focused on the consequences of OATP1B1 variants to statin disposition in vitro and in vivo and would suggest that genetic variability in SLCO1B1 has important implications for statin pharmacokinetics, risk for statin-induced myopathy, and modulation of statin treatment response. This review describes what is currently known regarding SLCO1B1 genotype, OATP1B1 protein expression and interindividual and interethnic consequences to drug disposition, with particular focus on statin pharmacokinetics and implications for drug response and toxicity.

SLCO1B1 polymorphism markedly affects the pharmacokinetics of lovastatin acid

OBJECTIVE

Organic anion transporting polypeptide 1B1 (OATP1B1, encoded by SLCO1B1 gene) is a hepatic uptake transporter, and its genetic variability is associated with pharmacokinetics and muscle toxicity risk of simvastatin. We examined the possible effects of variations in the SLCO1B1 gene on the pharmacokinetics of lovastatin in a prospective genotype panel study.

PARTICIPANTS AND METHODS

Seven healthy volunteers with the SLCO1B1*1B/*1B genotype, five with the SLCO1B1*5/*15 or *15/*15 genotype, and 15 with the SLCO1B1*1A/*1A genotype (controls) were recruited. Each study participant ingested a single 40-mg dose of lovastatin. Plasma concentrations of lovastatin (inactive lactone) and its active metabolite lovastatin acid were measured up to 24 h.

RESULTS

In the SLCO1B1*5/*15 or *15/*15 genotype group, the geometric mean Cmax and AUC0-24 of lovastatin acid were 340 and 286% of the corresponding values in the SLCO1B1*1A/*1A (reference) genotype group (P<0.005). In contrast, the AUC0-24 of lovastatin acid in the SLCO1B1*1B/*1B genotype group was only 68% of that in the reference genotype group (P=0.03). No statistically significant association was observed between the SLCO1B1 genotype and the pharmacokinetics of lovastatin lactone.

CONCLUSION

SLCO1B1*5/*15 and *15/*15 genotypes markedly increase the exposure to active lovastatin acid, but have no significant effect on lovastatin lactone, similar to their effects on simvastatin and simvastatin acid. Accordingly, it is probable that the risk of muscle toxicity during lovastatin treatment is increased in individuals carrying the SLCO1B1*5 or *15 allele. The SLCO1B1*1B/*1B genotype is associated with reduced lovastatin acid concentrations, consistent with enhanced hepatic uptake.

Pharmacokinetic Properties of Single- and Multiple-Dose Pitavastatin Calcium Tablets in Healthy Chinese Volunteers

BACKGROUND

Pitavastatin is a newly developed 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitor approved for the treatment of hyperlipidemia. Pharmacokinetic properties of pitavastatin have been studied previously.

OBJECTIVE

To investigate the pharmacokinetic properties of pitavastatin in healthy Chinese volunteers after single-dose and multiple-dose administration.

METHODS

An open-label, randomized, single-dose and multiple-dose study was conducted in healthy Chinese volunteers. The study included 4 stages, each separated with a 5-day washout period. A randomized, 3-way crossover design was carried out in Stages 1 to 3 for the single-dose study. Eligible subjects were randomized to receive a single 1 mg, 2 mg, or 4 mg pitavastatin calcium tablet. Blood samples were obtained predose and up to 36 hours following dosing. In Stage 4 the subjects received a 2-mg pitavastatin calcium tablet once daily for 6 days. At the last day of multiple dosing, blood samples were collected predose and up to 48 hours following dosing. Plasma pitavastatin was quantified by a validated liquid chromatography tandem mass spectrometry method. Tolerability was assessed by the adverse events, physical examination, 12-lead ECG, and laboratory tests.

RESULTS

Twelve volunteers (6 male and 6 female) were enrolled in the study and 11 of them completed all 4 study stages. Following a single dose of 1 mg, 2 mg, and 4 mg, the mean (SD) Tmax values were 0.63 (0.17) hours, 0.65 (0.17) hours, and 0.79 (0.36) hours, respectively; the corresponding Cmax values were 66.80 (16.32) ng/mL, 106.09 (31.59) ng/mL, and 232.91 (66.42) ng/mL, respectively. AUC0-36 values were 190.04 (38.97) ng/mL/h, 307.87 (57.94) ng/mL/h, and 785.10 (166.08) ng/mL/h, respectively, whereas t1/2 values were 10.99 (2.70) hours, 9.52 (2.58) hours, and 10.38 (4.28) hours, respectively. The AUC and Cmax showed dose proportionality after single dosing according to linear-regression analysis. In the multiple-dose study, a rapid absorption (Tmax of 0.68 [0.20] hours) and marked peak concentration of 90.99 (36.88) ng/mL were observed. AUC0-48 and AUCss were 306.28 (130.02) ng/mL/h and 256.16 (116.34) ng/mL/h, respectively. The elimination half-life after multiple dosing was significantly prolonged, which amounted to 13.31 (2.58) hours. Comparison of the pharmacokinetic parameters between the male and female groups revealed no significant differences.

CONCLUSIONS

In healthy Chinese volunteers, single dosing of 1 mg, 2 mg, and 4 mg pitavastatin resulted in linear plasma pharmacokinetic properties. Compared with single dosing, multiple dosing of pitavastatin showed different distribution and elimination characteristics. Sex did not appear to affect the pharmacokinetic properties of pitavastatin. Chictr.org identifier: ChiCTR-OO-13004294.

Do MDR1 and SLCO1B1 polymorphisms influence the therapeutic response to atorvastatin? A study on a cohort of Egyptian patients with hypercholesterolemia

BACKGROUND

Statins are among the most prescribed drugs worldwide to reduce the risk of cardiovascular events. Interindividual variability in drug response is a major clinical problem and is of concern during drug development. Statins, such as atorvastatin, are taken orally and access to their site of action in the liver is greatly facilitated by both intestinal and hepatic transporters.

OBJECTIVE

To examine the impact of polymorphisms of the multidrug resistance 1(MDR1) and solute carrier organic anion transporter 1B1 (SLCO1B1) genes on the therapeutic response to atorvastatin as well as the presence of gender-gene interaction.

METHODS

Serum lipid levels were determined at baseline and 4 weeks following 40 mg/day atorvastatin treatment in 50 Egyptian hypercholesterolemic patients (27 males and 23 females). Identification of MDR1 C3435T and SLCO1B1 A388G gene polymorphisms was performed using a polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) method.

RESULTS

Treatment with atorvastatin resulted in a mean reduction of total cholesterol (TC), low density lipoprotein cholesterol (LDL-C), and triglyceride (TG) of 8.7 %, 9.2 %, and 4.1 %, respectively, and a mean increase of high density lipoprotein cholesterol (HDL-C) of 1 %. Baseline and post-treatment HDL-C levels were statistically significantly higher in the MDR 1 TT homozygotes when compared with the CC wild type. The percentage change in TC, LDL-C, TG, and HDL-C did not show any statistically significant difference when compared among the different MDR 1 C3435T or SLCO1B1 A388G genotypes. The SLCO1B1 GG homozygotes showed a decrease in TG, whereas there was an increase in TG following atorvastatin treatment in AA and AG carriers in females; however, males did not show any statistically significant difference. There was no statistically significant association between either the coronary artery disease (CAD) risk factors (family history of CAD, hypertension, diabetes mellitus, smoking) or concomitant medications with the percentage change in different lipid parameters.

CONCLUSION

MDR1 C3435T was associated with baseline and post-treatment HDL-C variation. SLCO1B1 A388G showed gender-related effects on TG change following atorvastatin treatment. None of the comorbidities or the concomitant medications influenced the percentage change of lipid parameters following atorvastatin treatment. The results of this study may lead to an improved understanding of the genetic determinants of lipid response to atorvastatin treatment.

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.

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.

Influence of the functional polymorphisms in the organic anion transporting polypeptide 1B1 in the susceptibility to colorectal cancer

Colorectal cancer is an important cause of death throughout the world, and its etiology involves the interaction of genetic and environmental factors. Transporter proteins are important in protecting organs from xenobiotics or toxins. Organic anion-transporting polypeptide 1B1 (OATP1B1) plays role in hepatic uptake and clearance of albumin-bound amphipathic organic compounds, including endogen substances, drugs, or xenobiotics. The SLCO1B1 gene expressing OATP1B1 is highly polymorphic. Up to now, SLCO1BI variants were the focus of several investigations on drug pharmacokinetics and cancer susceptibility. However, no information has been available on association between SLCO1B1 and colorectal cancer risk. Therefore, the study aims to investigate the relationship between colorectal cancer and the functional common variants of SLCO1B1 (388 A>G, -11187 G>A, 521 T>C) and to estimate the prevalence of these variants in the Turkish population. To that end, the distributions of the variants were determined in 100 patients with colorectal cancer and 150 healthy volunteers. SLCO1B1 521 T>C was statistically significantly associated with colorectal cancer risk (odds ratio [OR]=2.66; 95% confidence interval [CI]=1.31-5.41; p=0.0057). In haplotype-based analysis, SLCO1B1 haplotype G(388)-T(11187)-T(521) might be associated with the development of colorectal cancer (OR=4.26; 95% CI=1.62-11.16; p=0.002). We believe that the findings may be beneficial to the development of efficacious preventive strategies and therapies for colorectal cancer.

Ethnic variability in the plasma exposures of OATP1B1 substrates such as HMG-CoA reductase inhibitors: a kinetic consideration of its mechanism

Because the plasma exposure levels of rosuvastatin in Asians are generally twice those in Caucasians, the starting dose for Asians in the United States is set to half of that for non-Asians. However, the precise role of ethnicity in the clearance of rosuvastatin has not yet been clarified. This review focuses on ethnic variability in the clinical pharmacokinetics of 3-hydroxy-3-methylglutaryl co-enzyme A (HMG-CoA) reductase inhibitors (statins) and angiotensin II receptor antagonists. The mechanisms of such variability are discussed quantitatively, with building a hypothetical model for pravastatin, and validated against other statins. Our analyses suggest that the ethnic variability in the plasma exposure of statins cannot be explained only by the difference in the allele frequencies of organic anion-transporting polypeptide (OATP)1B1 and breast cancer resistance protein (BCRP), and the intrinsic ethnic variability in the activity of OATP1B1 (the ratio of Japanese/Caucasians is 0.584) must be considered. Further work and validation with additional data will clarify the applicability of this model to other OATP1B1 substrates.

Simple LC-MS/MS methods for simultaneous determination of pitavastatin and its lactone metabolite in human plasma and urine involving a procedure for inhibiting the conversion of pitavastatin lactone to pitavastatin in plasma and its application to a pharmacokinetic study

Sometimes, drugs and their metabolites in plasma may convert to each other. This phenomenon is called interconversion, which may result in the instability problem of the plasma samples. The instability problem caused by interconversion of the co-existing metabolites may often be ignored, since there is no drug metabolite in the quality control samples prepared for method validation. Pitavastatin lactone (Pi-LAC), a main metabolite of pitavastatin (Pi), is very unstable and easily converted to Pi in plasma. In this paper, simple and rapid LC-ESI-MS/MS methods were developed for the simultaneous determination of Pi and Pi-LAC in human plasma and urine. The sample stability was examined under different conditions. The interconversion of Pi and Pi-LAC was prevented by adding a pH 4.2 buffer solution to the freshly collected plasma samples. Detection was performed using an electrospray ionization (ESI) operating in positive ion multiple reaction monitoring mode by monitoring the ion transitions from m/z 422.2→290.3 (Pi), 404.2→290.3 (Pi-LAC) and m/z 611.3→423.2 (candesartan cilextetil, the internal standard), respectively. The calibration curve of Pi and Pi-LAC in both human plasma and urine showed good linearity over the concentration range of 0.1-200 ng/mL. The established methods were successfully applied to a pharmacokinetic study of pitavastatin calcium tablets in healthy Chinese volunteers after oral administration of 1, 2 and 4 mg single and multiple doses of pitavastatin calcium. The pharmacokinetic parameters of Pi and Pi-LAC in Chinese volunteers were given respectively. The urinary excretion profiles of Pi and Pi-LAC in Chinese volunteers were also presented. After receiving a single 4 mg oral dose of pitavastatin calcium, the average cumulative urinary excretion percentages of Pi and Pi-LAC in Chinese volunteers were (0.41 ± 0.16)% and (6.1 ± 5.0)%, respectively.

Impact of ABCC2, ABCG2 and SLCO1B1 polymorphisms on the pharmacokinetics of pitavastatin in humans

Pitavastatin, a 3-hydroxyl-3-methylglutaryl-coenzyme A reductase inhibitor is distributed to the liver, a target organ of action and excreted mainly into the bile. To investigate the impact of influx (OATP1B1) and efflux (MRP2, BCRP) transporter alleles on its disposition, the pharmacokinetic (PK) parameters were compared among the following groups: SLCO1B1 (*15 carrier and non-carrier), ABCC2 (G1249A, C3972T, C-24T, G1549A, and G1774T), and ABCG2 (C421A) single nucleotide polymorphisms in 45 healthy Korean volunteers. Pitavastatin AUC(last) was higher in individuals carrying the SLCO1B1*15 allele than those not carrying it (144.1 ± 55.3 vs. 84.7 ± 25.7 h·ng/mL [mean ± SD], p = 0.002). The AUC(last) varied significantly according to the ABCC2 C-24T allele (103.4 ± 42.2, 80.2 ± 23.8, and 39.0 h·ng/mL in CC, CT and TT, respectively; p = 0.027). Other SNPs of ABCC2 and ABCG2 were not significant. The effect of these transporters and body weight on the AUC(last) and C(max) were tested, and only SLCO1B1 and ABCC2 C-24T genotypes were significant factors by analysis of covariance. These variants accounted for almost 50% of the variation in AUC(last) and C(max) of pitavastatin. Therefore, ABCC2 C-24T was significantly associated with pitavastatin human PK when the known effect of SLCO1B1*15 was also considered.

OATPs, OATs and OCTs: the organic anion and cation transporters of the SLCO and SLC22A gene superfamilies

The human organic anion and cation transporters are classified within two SLC superfamilies. Superfamily SLCO (formerly SLC21A) consists of organic anion transporting polypeptides (OATPs), while the organic anion transporters (OATs) and the organic cation transporters (OCTs) are classified in the SLC22A superfamily. Individual members of each superfamily are expressed in essentially every epithelium throughout the body, where they play a significant role in drug absorption, distribution and elimination. Substrates of OATPs are mainly large hydrophobic organic anions, while OATs transport smaller and more hydrophilic organic anions and OCTs transport organic cations. In addition to endogenous substrates, such as steroids, hormones and neurotransmitters, numerous drugs and other xenobiotics are transported by these proteins, including statins, antivirals, antibiotics and anticancer drugs. Expression of OATPs, OATs and OCTs can be regulated at the protein or transcriptional level and appears to vary within each family by both protein and tissue type. All three superfamilies consist of 12 transmembrane domain proteins that have intracellular termini. Although no crystal structures have yet been determined, combinations of homology modelling and mutation experiments have been used to explore the mechanism of substrate recognition and transport. Several polymorphisms identified in members of these superfamilies have been shown to affect pharmacokinetics of their drug substrates, confirming the importance of these drug transporters for efficient pharmacological therapy. This review, unlike other reviews that focus on a single transporter family, briefly summarizes the current knowledge of all the functionally characterized human organic anion and cation drug uptake transporters of the SLCO and the SLC22A superfamilies.

Effects of grapefruit juice and SLCO1B1 388A>G polymorphism on the pharmacokinetics of pitavastatin

Pitavastatin undergoes little hepatic metabolism but it is a substrate for uptake and efflux transporters, particularly OATP1B1 (gene SLCO1B1). A previous study in 8 Japanese healthy subjects showed that co-administration with grapefruit juice (GFJ) resulted in a small increase in systemic exposure to pitavastatin. We examined whether common polymorphisms in SLCO1B1 might influence the pharmacokinetics of pitavastatin or the interaction with GFJ. Twelve Chinese healthy male volunteers took pitavastatin 2 mg orally with water or with GFJ on separate occasions and plasma concentrations of pitavastatin acid and lactone were measured over 48 h. GFJ increased the mean area under the plasma concentration-time curve (AUC0-48 h) for both pitavastatin acid and lactone by 14% (p<0.05). Subjects with SLCO1B1 *1b/*1b haplotype (388GG-521TT) had 47% and 44% higher systemic exposure for pitavastatin acid and lactone than the SLCO1B1 *1a carriers (388AA/AG-521TT, p<0.05 and p=0.005, respectively). The SLCO1B1 388A>G polymorphism, which increases transporter activity for some statins, was associated with higher plasma levels of pitavastatin acid and lactone in subjects with the homozygous variant indicating decreased hepatic uptake. Co-administration of pitavastatin with GFJ resulted in a small but significant increase in plasma levels in healthy Chinese subjects.

Effect of CYP2C9 and SLCO1B1 polymorphisms on the pharmacokinetics and pharmacodynamics of nateglinide in healthy Chinese male volunteers

PURPOSE

Nateglinide is commonly used in the treatment of patients with type 2 diabetes mellitus. Our objective was to assess the association between CYP2C9 and SLCO1B1 polymorphisms and the metabolism of nateglinide in healthy Chinese male volunteers.

METHODS

A total of 35 healthy Chinese male volunteers with different CYP2C9 and SLCO1B1 genotypes were given a single oral dose of 120 mg nateglinide. Plasma concentrations of nateglinide and blood glucose level were measured up to 8 h.

RESULTS

In subjects with the CYP2C9*1/*3 & 521TT, CYP2C9*1/*1 & 521TC/CC and CYP2C9*1/*3 & 521TC genotype, AUC(0-∞) of nateglinide was 56 %, 34 % and 56 % higher (P = 0.002, P = 0.041 and P = 0.013, respectively), and the CL/F of nateglinide was 35 %, 11 % and 36 % lower (P = 0.000, P = 0.003 and P = 0.002, respectively) than that in the reference group. When only considering 521 T>C polymorphism, it had no significant association with the pharmacokinetics of nateglinide. CYP2C9*3 and 521 T>C polymorphisms were the significant predictors of the AUC(0-∞) and CL/F of nateglinide (adjusted multiple R(2) = 34 % and 43 %, respectively) according to multiple linear regression analyses, but they have no significant association with changes in the blood glucose-lowering effect of nateglinide.

CONCLUSIONS

Both SLCO1B1 521 T>C and the CYP2C9*3 polymorphisms can significantly affect the pharmacokinetics of nateglinide, but they could only partially explain the interindividual variability of plasma concentration of nateglinide. Moreover, 521 T>C and the CYP2C9*3 polymorphisms have no effect on pharmacodynamics of nateglinide in healthy Chinese male subjects.

Pleiotropic effects of pitavastatin

3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitors (statins) are established first line treatments for hypercholesterolaemia. In addition to the direct effects of statins in reducing concentrations of atherogenic low density lipoprotein cholesterol (LDL-C), several studies have indicated that the beneficial effects of statins may be due to some of their cholesterol-independent, multiple (pleiotropic) effects which may differ between different members of the class. Pitavastatin is a novel synthetic lipophilic statin that has a number of pharmacodynamic and pharmacokinetic properties distinct from those of other statins, which may underlie its potential pleiotropic benefits in reducing cardiovascular risk factors. This review examines the principal pleiotropic effects of pitavastatin on endothelial function, vascular inflammation, oxidative stress and thrombosis. The article is based on a systematic literature search carried out in December 2010, together with more recent relevant publications where appropriate. The available data from clinical trials and in vitro and animal studies suggest that pitavastatin is not only effective in reducing LDL-C and triglycerides, but also has a range of other effects. These include increasing high density lipoprotein cholesterol, decreasing markers of platelet activation, improving cardiac, renal and endothelial function, and reducing endothelial stress, lipoprotein oxidation and, ultimately, improving the signs and symptoms of atherosclerosis. It is concluded that the diverse pleiotropic actions of pitavastatin may contribute to reducing cardiovascular morbidity and mortality beyond that achieved through LDL-C reduction.

Organic anion transporting polypeptides OATP1B1 and OATP1B3 and their genetic variants influence the pharmacokinetics and pharmacodynamics of raloxifene

Background

Raloxifene, a selective estrogen receptor modulator, exhibits quite large and unexplained interindividual variability in pharmacokinetics and pharmacodynamics. The aim of this study was to determine the role of organic-anion transporting polypeptides OATP1B1 and OATP1B3 and their genetic variants in the pharmacokinetics and pharmacodynamics of raloxifene.

Methods

To test the role of OATP1B1 and OATP1B3 transporters on hepatic uptake of raloxifene and its metabolites an in vitro model of Chinese Hamster Ovary cells expressing OATP1B1 or OATP1B3 was employed. The influence of OATP1B1 and OATP1B3 genetic variants on in vivo pharmacokinetics and pharmacodynamics was evaluated in 53 osteoporotic postmenopausal women treated with raloxifene.

Results

Our in vitro results showed that raloxifene and two of the three metabolites, raloxifene-4'-β-glucuronide (M2) and raloxifene-6,4'-diglucuronide (M3), interact with OATP1B1 and OATP1B3. Higher M3 and total raloxifene serum concentrations in patients correlated with lower serum levels of bone resorption marker, serum C-terminal telopeptide fragments of type I collagen, indicating a higher antiresorptive effect of raloxifene. Higher concentrations of M2 correlated with higher increase of lumbar spine bone mineral density supporting the raloxifene vertebral fracture specific protection effect. Finally, raloxifene, M3 and total raloxifene serum concentrations were significantly higher in patients with SLCO1B1 c.388A > G polymorphism and *1b haplotype implicating a considerable genetic effect on pharmacokinetics and pharmacodynamics of raloxifene.

Conclusions

These findings indicate that SLCO1B1 c.388A > G polymorphism could play an important role in pharmacokinetics and pharmacodynamics of raloxifene.

Are all statins the same? Focus on the efficacy and tolerability of pitavastatin

Pitavastatin is the newest member of the HMG-CoA reductase inhibitor family and is approved as adjunctive therapy to diet to reduce elevated levels of total cholesterol, low-density lipoprotein (LDL) cholesterol, apolipoprotein (Apo) B, and triglycerides and to increase levels of high-density lipoprotein (HDL) cholesterol in adult patients with primary hyperlipidemia or mixed dyslipidemia. Pitavastatin undergoes minimal metabolism by cytochrome P450 (CYP) enzymes and, therefore, has a low propensity for drug-drug interactions with drugs metabolized by CYP enzymes or the CYP3A4 substrate grapefruit juice. In clinical trials, pitavastatin potently and consistently reduced serum levels of total, LDL, and non-HDL cholesterol, and triglycerides in patients with primary hypercholesterolemia where diet and other non-pharmacological measures were inadequate. Mean reductions from baseline in serum total and LDL cholesterol and triglyceride levels were 21-32%, 30-45%, and 10-30%, respectively. Moreover, a consistent trend towards increased HDL cholesterol levels of 3-10% was seen. Long-term extension studies show that the beneficial effects of pitavastatin are maintained for up to 2 years. Pitavastatin produces reductions from baseline in serum total and LDL cholesterol levels to a similar extent to those seen with the potent agent atorvastatin and to a greater extent than those seen with simvastatin or pravastatin. In the majority of other studies comparing pitavastatin and atorvastatin, no significant differences in the favorable effects on lipid parameters were seen, although pitavastatin was consistently associated with trends towards increased HDL cholesterol levels. Pitavastatin also produces beneficial effects on lipids in patients with type 2 diabetes mellitus and metabolic syndrome without deleterious effects on markers of glucose metabolism, such as fasting blood glucose levels or proportion of glycosylated hemoglobin. Pitavastatin appears to exert a number of beneficial effects on patients at risk of cardiovascular events independent of lipid lowering. In the JAPAN-ACS (Japan Assessment of Pitavastatin and Atorvastatin in Acute Coronary Syndrome) study, pitavastatin was non-inferior to atorvastatin at reducing plaque volume in patients with ACS undergoing percutaneous coronary intervention. Further beneficial effects, including favorable effects on the size and composition of atherosclerotic plaques, improvements in cardiovascular function, and improvements in markers of inflammation, oxidative stress, and renal function, have been demonstrated in a number of small studies. Pitavastatin is generally well tolerated in hyperlipidemic patients with or without type 2 diabetes, with the most common treatment-related adverse events being musculoskeletal or gastrointestinal in nature. Increases in plasma creatine kinase levels were seen in <5% of pitavastatin recipients and the incidence of myopathy or rhabdomyolysis was extremely low. In summary, pitavastatin, the latest addition to the statin family, produces potent and consistent beneficial effects on lipids, is well tolerated, and has a favorable pharmacokinetic profile. The combination of a potent decrease in total and LDL cholesterol levels and increase in HDL cholesterol levels suggest that pitavastatin may produce substantial cardiovascular protection.

Comparison of the pharmacokinetics of pitavastatin by formulation and ethnic group: an open-label, single-dose, two-way crossover pharmacokinetic study in healthy Caucasian and Japanese men

BACKGROUND AND OBJECTIVES

Pitavastatin is a highly effective lipid-lowering drug (approved dose range 1-4 mg/day) with a distinctive metabolic pathway that has a low potential for drug interactions. The efficacy and safety of pitavastatin have been characterized in a broad clinical development programme conducted initially in Japanese patients. The objectives of the present study were to evaluate the pharmacokinetic bioequivalence of the European (EU) and Japanese (JP) formulations of pitavastatin 2 mg in healthy Japanese and Caucasian men, and to assess whether the bioavailability of each formulation was similar in the two ethnic groups.

METHODS

In this open-label, single-dose, two-way crossover pharmacokinetic study, healthy men aged 18-45 years were randomized to receive: the JP formulation of pitavastatin 2 mg followed by the EU formulation; or the EU formulation of pitavastatin 2 mg followed by the JP formulation. The main outcome measures were maximum plasma concentration (C(max)), area under the plasma concentration-time curve (AUC) during a dosage interval (τ) [AUC(τ)] and AUC from time zero to infinity (AUC(∞)) for pitavastatin and its main (inactive) metabolite pitavastatin lactone. Plasma concentrations of pitavastatin and pitavastatin lactone were determined using a validated liquid chromatography-tandem mass spectrometry method.

RESULTS

Forty-eight Caucasian and 12 Japanese men completed the study. Compared with the Japanese men, the Caucasian men were of greater mean body weight (76.1 vs 58.9 kg), height (180.8 vs 170.8 cm) and body mass index (23.2 vs 20.2 kg/m2). Geometric mean ratios (GMRs) of the pharmacokinetic parameters of pitavastatin demonstrated bioequivalence of the EU and JP formulations: GMRs and 90% confidence intervals (CIs) fell within the range 80-125% in Caucasian men and in Caucasian and Japanese groups combined for pitavastatin C(max) (combined analysis: GMR 103.1% [90% CI 96.0, 110.6]), AUC(τ) (GMR 99.6% [90% CI 95.5, 104.0]), and AUC(∞) (GMR 104.2% [90% CI 96.2, 112.8]). After adjusting for age and body weight in the pooled formulation analysis, bioequivalence between the Caucasian and Japanese groups was similarly demonstrated for pitavastatin C(max) (GMR 96.8% [90% CI 90.2, 103.8]), AUC(τ) (GMR 98.3% [90% CI 94.2, 102.7]) and AUC(∞) (GMR 85.9% [90% CI 81.1, 91.0]).

CONCLUSION

The EU and JP formulations of pitavastatin showed pharmacokinetic bioequivalence, and there were no clinically relevant differences in exposure to pitavastatin between Caucasian and Japanese participants when differences in body weight were taken into account.

Membrane transporters in drug development

Membrane transporters have wide, but specific tissue distributions. They can impact on multiple endogenous and xenobiotic processes. Knowledge and awareness within the pharmaceutical industry of their impact on drug absorption, distribution, metabolism and elimination (ADME) and drug safety is growing rapidly. Clinically important transporter-mediated drug-drug interactions (DDIs) have been observed. Up to nine diverse transporters are implicated in the DDIs of a number of widely prescribed drugs, posing a significant challenge to the pharmaceutical industry. There is a complex interplay between multiple transporters and/or enzymes in the ADME and pharmacogenomics of drugs. Integrating these different mechanisms to understand their relative contributions to ADME is a key challenge. Many different factors complicate the study of membrane transporters in drug development. These include a lack of specific substrates and inhibitors, non-standard in vitro tools, and competing/complementary mechanisms (e.g. passive permeability and metabolism). Discovering and contextualizing the contribution of membrane transporters to drug toxicity is a significant new challenge. Drug interactions with key membrane transporters are routinely assessed for central nervous system (CNS) drug discovery therapies, but are not generally considered across the wider drug discovery. But, there is interest in utilizing membrane transporters as drug delivery agents. Computational modeling approaches, notably physiology-based/pharmacokinetic (PB/PK) modeling are increasingly applied to transporter interactions, and permit integration of multiple ADME mechanisms. Because of the range of tissues and transporters of interest, robust transporter, in vitro to in vivo, scaling factors are required. Empirical factors have been applied, but absolute protein quantitation will probably be required.

Genetic polymorphisms of OATP transporters and their impact on intestinal absorption and hepatic disposition of drugs

There is convincing evidence that many organic anion transporting polypeptide (OATP) transporters influence the pharmacokinetics and pharmacological efficacy of their substrate drugs. Each OATP family member has a unique combination of tissue distribution, substrate specificity and mechanisms of gene expression. Among them, OATP1B1, OATP1B3 and OATP2B1 have been considered as critical molecular determinants of the pharmacokinetics of a variety of clinically important drugs. Liver-specific expression of OATP1B1 and OATP1B3 contributes to the hepatic uptake of drugs from the portal vein, and OATP2B1 may alter their intestinal absorption as well as hepatic extraction. Accordingly, changes in function and expression of these three OATPs owing to genetic polymorphisms may lead to altered pharmacological effects, including decreased drug efficacy and increased risk of adverse effects. Association of genetic polymorphisms in OATP genes with alterations in the pharmacokinetic properties of their substrate drugs has been reported; however, there still exists a degree of discordance between the reported outcomes in different clinical settings. For better understanding of the clinical relevance of genetic polymorphisms of OATP1B1, OATP1B3 and OATP2B1, the present review focuses on the association of the genotypes of these OATPs with in vitro activity changes and in vivo clinical outcomes of substrate drugs.

The effect of herbal medicine danshensu and ursolic acid on pharmacokinetics of rosuvastatin in rats

The aim of this study was to explore potential herb-drug interaction between danshensu or ursolic acid and rosuvastatin. Compared to the control group given rosuvastatin alone, the concurrent use of danshensu (46 mg/kg) or ursolic acid (80 mg/kg) prior to the oral administration of rosuvastatin (100 mg/kg) increased the systemic exposure of rosuvastatin more than twofold. The plasma clearance of rosuvastatin was reduced to more than 57% in the presence of danshensu or ursolic acid. Rosuvastatin is minimally metabolized in the CYP2C9 isoenzyme pathway and to an even lesser extent in the CYP2C19 isoenzyme pathway. Rosuvastatin is a substrate of drug transporters such as human OATP1B1, OATP 1B3, OATP 1A2, BCRP and NTCP. Therefore, the present results suggested that the potential drug interaction between danshensu or ursolic acid and rosuvastatin may be mediated by one or more transporters (OATP1B1, OATP 1B3, OATP 1A2, BCRP and NTCP) and/or CYPs.

Pharmacogenetics of OATP transporters reveals that SLCO1B1 c.388A>G variant is determinant of increased atorvastatin response

Aims

The relationship between variants in SLCO1B1 and SLCO2B1 genes and lipid-lowering response to atorvastatin was investigated.

Material and Methods

One-hundred-thirty-six unrelated individuals with hypercholesterolemia were selected and treated with atorvastatin (10 mg/day/4 weeks). They were genotyped with a panel of ancestry informative markers for individual African component of ancestry (ACA) estimation by SNaPshot^® and SLCO1B1 (c.388A>G, c.463C>A and c.521T>C) and SLCO2B1 (−71T>C) gene polymorphisms were identified by TaqMan^® Real-time PCR.

Results

Subjects carrying SLCO1B1 c.388GG genotype exhibited significantly high low-density lipoprotein (LDL) cholesterol reduction relative to c.388AA+c.388AG carriers (41 vs. 37%, p = 0.034). Haplotype analysis revealed that homozygous of SLCO1B1*15 (c.521C and c.388G) variant had similar response to statin relative to heterozygous and non-carriers. A multivariate logistic regression analysis confirmed that c.388GG genotype was associated with higher LDL cholesterol reduction in the study population (OR: 3.2, CI95%:1.3–8.0, p < 0.05).

Conclusion

SLCO1B1 c.388A>G polymorphism causes significant increase in atorvastatin response and may be an important marker for predicting efficacy of lipid-lowering therapy.

Effects of SLCO1B1 polymorphisms on the pharmacokinetics and pharmacodynamics of repaglinide in healthy Chinese volunteers

PURPOSE

Repaglinide is commonly used in the treatment of patients with type 2 diabetes mellitus to reduce postprandial hyperglycemia. The objective of this research was to study the effects of SLCO1B1 polymorphisms on the pharmacokinetics and pharmacodynamics of repaglinide in healthy Chinese volunteers.

METHODS

A total of 22 healthy young male participants were recruited from a pool of pharmacogenetically characterized participants genotyped for SLCO1B1, CYP3A4, and CYP2C8 SNPs by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP). Volunteers with CYP2C8*3 and CYP3A4*4 alleles were excluded from the clinical study. Then selected volunteers took part in the clinical pharmacokinetic study, receiving 2 mg repaglinide.

RESULTS

Healthy participants with SLCO1B1*1A/*1B or *1A/*1A genotype and SLCO1B1 *15/*1A or *5/*1A genotype had significantly higher AUC(0-∞) than participants with SLCO1B1*1B/*1B genotype, with the former showing an increase over the latter of 39.81 and 42.09%, respectively (P = 0.028, 0.032). The clearance in the former two genotype groups was significantly attenuated (by 27.39 and 28.55%, respectively) compared with individuals with SLCO1B1*1B/*1B genotype (P = 0.015, 0.019). No significant differences in blood glucose-lowering effect were observed among three genotype groups.

CONCLUSIONS

SLCO1B1*1B/*1B genotype is associated with reduced pharmacokinetic exposure after a single dose oral administration of 2 mg repaglinide, including decreased AUC(0-∞) and increased clearance of repaglinide. Moreover, this polymorphism of SLCO1B1 has significant influence on the pharmacokinetics of repaglinide, but no effects on its pharmacodynamics.

Organic anion transporting polypeptide 1B1: a genetically polymorphic transporter of major importance for hepatic drug uptake

The importance of membrane transporters for drug pharmacokinetics has been increasingly recognized during the last decade. Organic anion transporting polypeptide 1B1 (OATP1B1) is a genetically polymorphic influx transporter expressed on the sinusoidal membrane of human hepatocytes, and it mediates the hepatic uptake of many endogenous compounds and xenobiotics. Recent studies have demonstrated that OATP1B1 plays a major, clinically important role in the hepatic uptake of many drugs. A common single-nucleotide variation (coding DNA c.521T>C, protein p.V174A, rs4149056) in the SLCO1B1 gene encoding OATP1B1 decreases the transporting activity of OATP1B1, resulting in markedly increased plasma concentrations of, for example, many statins, particularly of active simvastatin acid. The variant thereby enhances the risk of statin-induced myopathy and decreases the therapeutic indexes of statins. However, the effect of the SLCO1B1 c.521T>C variant is different on different statins. The same variant also markedly affects the pharmacokinetics of several other drugs. Furthermore, certain SLCO1B1 variants associated with an enhanced clearance of methotrexate increase the risk of gastrointestinal toxicity by methotrexate in the treatment of children with acute lymphoblastic leukemia. Certain drugs (e.g., cyclosporine) potently inhibit OATP1B1, causing clinically significant drug interactions. Thus, OATP1B1 plays a major role in the hepatic uptake of drugs, and genetic variants and drug interactions affecting OATP1B1 activity are important determinants of individual drug responses. In this article, we review the current knowledge about the expression, function, substrate characteristics, and pharmacogenetics of OATP1B1 as well as its role in drug interactions, in parts comparing with those of other hepatocyte-expressed organic anion transporting polypeptides, OATP1B3 and OATP2B1.

Pitavastatin for the treatment of primary hyperlipidemia and mixed dyslipidemia

Pitavastatin is a new, synthetic member of the statin class of lipid-lowering drugs. Compared with other available statins, it has a unique cyclopropyl group on its base structure that is believed to increase 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibition by a factor of five and to significantly increase the transcription and activity of LDL receptors. Pitavastatin is primarily metabolized via glucuronidation and is not a substrate for the cytochrome P450 3A4 enzyme, thus avoiding the potential for cytochrome P450-mediated drug-drug interactions. Clinical trials have shown that pitavastatin is comparable to atorvastatin and simvastatin in improving lipid measures, and more potent than pravastatin. Pitavastatin is effective in reducing triglycerides and increasing HDL-cholesterol, so it will be particularly beneficial in treating patients with mixed dyslipidemia. Its safety and adverse event profile is similar to that of other available statins, and it has an established history of use in Asia indicating tolerability and safety for treatment lasting up to 7 years.