The SLCO1B1*5 genetic variant is associated with statin-induced side effects

Mixed effects of OATP1B1, BCRP and NTCP polymorphisms on the population pharmacokinetics of pravastatin in healthy volunteers

1. Pravastatin is a 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitor used for the treatment of hyperlipidaemia. This study aims to investigate the effects of genetic polymorphisms in OATP1B1, BCRP and NTCP on pravastatin population pharmacokinetics in healthy Chinese volunteers using a non-linear mixed-effect modelling (NONMEM) approach. A two-compartment model with a first-order absorption and elimination described plasma pravastatin concentrations well. 2. Genetic polymorphisms of rs4149056 (OATP1B1) and rs2306283 (OATP1B1) were found to be associated with a significant (p < 0.01) decrease in the apparent clearance from the central compartment (CL/F), while rs2296651 (NTCP) increased CL/F to a significant degree (p < 0.01). The combination of these three polymorphisms reduced the inter-individual variability of CL/F by 78.8%. 3. There was minimal effect of rs2231137 (BCRP) and rs2231142 (BCRP) on pravastatin pharmacokinetics (0.01 < p < 0.05), whereas rs11045819 (OATP1B1), rs1061018 (BCRP) and rs61745930 (NTCP) genotypes do not appear to be associated with pravastatin pharmacokinetics based on the population model (p > 0.05). 4. The current data suggest that the combination of rs4149056, rs2306283 and rs2296651 polymorphisms is an important determinant of pravastatin pharmacokinetics.

SLCO1B1 Variants and Angiotensin Converting Enzyme Inhibitor (Enalapril)-Induced Cough: a Pharmacogenetic Study

Clinical observations suggest that incidence of cough in Chinese taking angiotensin converting enzyme inhibitors is much higher than other racial groups. Cough is the most common adverse reaction of enalapril. We investigate whether SLCO1B1 genetic polymorphisms, previously reported to be important determinants of inter-individual variability in enalapril pharmacokinetics, are associated with the enalapril-induced cough. A cohort of 450 patients with essential hypertension taking 10 mg enalapril maleate were genotyped for the functional SLCO1B1 variants, 388A > G (Asn130Asp, rs2306283) and 521T > C (Val174Ala, rs4149056). The primary endpoint was cough, which was recorded when participants were bothered by cough and respiratory symptoms during enalapril treatment without an identifiable cause. SLCO1B1 521C allele conferred a 2-fold relative risk of enalapril-induced cough (95% confidence interval [CI] = 1.34-3.04, P = 6.2 × 10(-4)), and haplotype analysis suggested the relative risk of cough was 6.94-fold (95% CI = 1.30-37.07, P = 0.020) in SLCO1B1*15/*15 carriers. Furthermore, there was strong evidence for a gene-dose effect (percent with cough in those with 0, 1, or 2 copy of the 521C allele: 28.2%, 42.5%, and 71.4%, trend P = 6.6 × 10(-4)). Our study highlights, for the first time, SLCO1B1 variants are strongly associated with an increased risk of enalapril-induced cough. The findings will be useful to provide pharmacogenetic markers for enalapril treatment.

Pharmacogenomics of hypertension and heart disease

Heart disease is a leading cause of death in the United States, and hypertension is a predominant risk factor. Thus, effective blood pressure control is important to prevent adverse sequelae of hypertension, including heart failure, coronary artery disease, atrial fibrillation, and ischemic stroke. Over half of Americans have uncontrolled blood pressure, which may in part be explained by interpatient variability in drug response secondary to genetic polymorphism. As such, pharmacogenetic testing may be a supplementary tool to guide treatment. This review highlights the pharmacogenetics of antihypertensive response and response to drugs that treat adverse hypertension-related sequelae, particularly coronary artery disease and atrial fibrillation. While pharmacogenetic evidence may be more robust for the latter with respect to clinical implementation, there is increasing evidence of genetic variants that may help predict antihypertensive response. However, additional research and validation are needed before clinical implementation guidelines for antihypertensive therapy can become a reality.

Pilot study of pharmacist-assisted delivery of pharmacogenetic testing in a primary care setting

AIM

To describe the rationale and design of a pilot program to implement and evaluate pharmacogenetic (PGx) testing in a primary care setting.

STUDY RATIONALE

Several factors have impeded the uptake of PGx testing, including lack of provider knowledge and challenges with operationalizing PGx testing in a clinical practice setting.

STUDY DESIGN

We plan to compare two strategies for the implementation of PGx testing: a pharmacist-initiated testing arm compared with a physician-initiated PGx testing arm. Providers in both groups will be required to attend an introduction to PGx seminar. Anticipated results: We anticipate that providers in the pharmacist-initiated group will be more likely to order PGx testing than providers in the physician-initiated group.

CONCLUSION

Overall, we aim to generate data that will inform an effective delivery model for PGx testing and to facilitate a seamless integration of PGx testing in primary care practices.

Association Between SLCO1B1 Gene T521C Polymorphism and Statin-Related Myopathy Risk: A Meta-Analysis of Case-Control Studies

Statin-related myopathy is an important adverse effect of statin which is classically unpredictable. The evidence of association between solute carrier organic anion transporter 1B1 (SLCO1B1) gene T521C polymorphism and statin-related myopathy risk remained controversial. This study aimed to investigate this genetic association. Databases of PubMed, EMBASE, Chinese Biomedical Literature Database (CBM), China National Knowledge Infrastructure (CNKI), Chinese Scientific Journals Database, and Wanfang Data were searched till June 17, 2015. Case-control studies investigating the association between SLCO1B1 gene T521C polymorphism and statin-related myopathy risk were included. The Newcastle-Ottawa Scale (NOS) was used for assessing the quality of included studies. Data were pooled by odds ratios (ORs) and their 95% confidence intervals (CIs). Nine studies with 1360 cases and 3082 controls were included. Cases of statin-related myopathy were found to be significantly associated with the variant C allele (TC + CC vs TT: OR = 2.09, 95% CI = 1.27-3.43, P = 0.003; C vs T: OR = 2.10, 95% CI = 1.43-3.09, P < 0.001), especially when statin-related myopathy was defined as an elevation of creatine kinase (CK) >10 times the upper limit of normal (ULN) or rhabdomyolysis (TC + CC vs TT: OR = 3.83, 95% CI = 1.41-10.39, P = 0.008; C vs T: OR = 2.94, 95% CI = 1.47-5.89, P = 0.002). When stratified by statin type, the association was significant in individuals receiving simvastatin (TC + CC vs TT: OR = 3.09, 95% CI = 1.64-5.85, P = 0.001; C vs T: OR = 3.00, 95% CI = 1.38-6.49, P = 0.005), but not in those receiving atorvastatin (TC + CC vs TT: OR = 1.31, 95% CI = 0.74-2.30, P = 0.35; C vs T: OR = 1.33, 95% CI = 0.57-3.12, P = 0.52). The available evidence suggests that SLCO1B1 gene T521C polymorphism is associated with an increased risk of statin-related myopathy, especially in individuals receiving simvastatin. Thus, a genetic test before initiation of statins may be meaningful for personalizing the treatment.

Genotype-based clinical trials in cardiovascular disease

Consensus practice guidelines and the implementation of clinical therapeutic advances are usually based on the results of large, randomized clinical trials (RCTs). However, RCTs generally inform us on an average treatment effect for a presumably homogeneous population, but therapeutic interventions rarely benefit the entire population targeted. Indeed, multiple RCTs have demonstrated that interindividual variability exists both in drug response and in the development of adverse effects. The field of pharmacogenomics promises to deliver the right drug to the right patient. Substantial progress has been made in this field, with advances in technology, statistical and computational methods, and the use of cell and animal model systems. However, clinical implementation of pharmacogenetic principles has been difficult because RCTs demonstrating benefit are lacking. For patients, the potential benefits of performing such trials include the individualization of therapy to maximize efficacy and minimize adverse effects. These trials would also enable investigators to reduce sample size and hence contain costs for trial sponsors. Multiple ethical, legal, and practical issues need to be considered for the conduct of genotype-based RCTs. Whether pre-emptive genotyping embedded in electronic health records will preclude the need for performing genotype-based RCTs remains to be seen.

Cardiovascular pharmacogenomics: current status and future directions

Drugs are widely used and highly effective in the treatment of heart disease. Nevertheless, in some instances, even drugs effective in a population display lack of efficacy or adverse drug reactions in individual patients, often in an apparently unpredictable fashion. This review summarizes the genomic factors now known to influence variability in responses to widely used cardiovascular drugs such as clopidogrel, warfarin, heparin and statins. Genomic approaches being used to discover new pathways in common cardiovascular diseases and thus potential new targets for drug development are described. Finally, the way in which this new information is likely to be used in an electronic medical record environment is discussed.

The role of mitochondria in statin-induced myopathy

BACKGROUND

Statins inhibit hydroxymethylglutaryl-coenzyme A reductase, decrease plasma low-density lipoprotein cholesterol and reduce cardiovascular morbidity and mortality. They can also exert adverse effects, mostly affecting skeletal muscle, ranging from mild myalgia to rhabdomyolysis.

MATERIALS AND METHODS

Based on a PubMed search until December 2014, this review summarizes studies on statin effects on muscle mitochondrial morphology and function in the context of myopathy.

RESULTS

Possible mechanisms of statin-induced myopathy include lower cholesterol synthesis and production of prenylated proteins, reduced dolichols and increased atrogin-1 expression. Statin-treated patients frequently feature decreased muscle coenzyme Q10 (CoQ10) contents, suggesting that statins might impair mitochondrial function. In cell cultures, statins diminish muscle oxygen consumption, promote mitochondrial permeability transient pore opening and generate apoptotic proteins. Animal models confirm the statin-induced decrease in muscle CoQ10, but reveal no changes in mitochondrial enzyme activities. Human studies yield contradictory results, with decreased CoQ10, elevated lipids, decreased enzyme activities in muscle and impaired maximal oxygen uptake in several but not all studies. Some patients are susceptible to statin-induced myopathy due to variations in genes encoding proteins involved in statin uptake and biotransformation such as the solute carrier organic anion transporter family member 1B1 (SLCO1B1) or cytochrome P450 (CYP2D6, CYP3A4, CYP3A5). Carriers for carnitine palmitoyltransferase II deficiency and McArdle disease also present with higher prevalence of statin-induced myopathy.

CONCLUSIONS

Despite the widespread use of statins, the pathogenesis of statin-induced myopathy remains unclear, requiring prospective randomized controlled trials with intensive phenotyping also for identifying strategies for its risk assessment, prevention and treatment.

Progress in understanding the genomic basis for adverse drug reactions: a comprehensive review and focus on the role of ethnicity

A major goal of the field of pharmacogenomics is to identify the genomic causes of serious adverse drug reactions (ADRs). Increasingly, genome-wide association studies (GWAS) have been used to achieve this goal. In this article, we review recent progress in the identification of genetic variants associated with ADRs using GWAS and discuss emerging themes from these studies. We also compare aspects of GWAS for ADRs to GWAS for common diseases. In the second part of the article, we review progress in performing pharmacogenomic research in multi-ethnic populations and discuss the challenges and opportunities of investigating genetic causes of ADRs in ethnically diverse patient populations.

ABCG2 gene polymorphisms as risk factors for atorvastatin adverse reactions: a case-control study

AIM

To explore the association between dose-related adverse drug reactions (ADRs) of atorvastatin and polymorphisms of ABCG2, taking into account the influence of CYP3A4 and SLCO1B1 genes.

MATERIALS & METHODS

Sixty patients who experienced atorvastatin dose-related ADRs and 90 matched patients without ADRs were enrolled in the study. Genotyping for ABCG2 421C > A, CYP3A4*22, SLCO1B1 388A > G, SLCO1B1 521T > C variants was performed by real-time PCR.

RESULTS

Patients with ABCG2 421CA or AA genotypes had 2.9 times greater odds of developing atorvastatin dose-dependent ADRs (OR: 2.91; 95% CI: 1.22-6.95; p = 0.016) than those with ABCG2 421CC genotype. After adjustments for clinical and genetic risk factors, ABCG2 remained a statistically significant predictor of adverse drug reactions (OR: 2.75; 95% CI: 1.1-6.87; p = 0.03;). Also, carriers of SLCO1B1 521 TC or CC genotypes had 2.3 greater odds (OR: 1.03-4.98; 95% CI: 1.03-4.98; p = 0.043) of experiencing ADRs caused by atorvastatin in comparison with carriers of SLCO1B1 521 TT genotype.

CONCLUSION

Our study demonstrated an association between atorvastatin-induced ADRs and genetic variants in the ABCG2 gene.

Statins and the neuromuscular system: a neurologist's perspective

Statins intolerance is mainly due to their side effects on the neuromuscular system (primarily muscle). It has become an important issue because of the major cardiovascular risk reduction of this class of drugs. However, the facts related to these side effects are sometimes under-recognized or controversial. A literature review of the recent developments in the field is given. The clinical definition of statin myopathy and its presentation are not suitable for the myology field. Management and prevention are not validated. More genetic risk factors need to be established. Neurologists should become more involved in statin intolerance evaluation and management.

Cardiovascular Pharmacokinetics, Pharmacodynamics, and Pharmacogenomics for the Clinical Practitioner

Current clinical cardiovascular practice requires a clinician to have a strong foundation in multiple aspects of pharmacology. Modern cardiovascular regimens are complex, and optimal management, application of evolving guidelines, and adoption of new therapies build off a more basic understanding of pharmacokinetics and pharmacodynamics. In addition, it is likely time to add a third pillar into this discussion, the expanding field of pharmacogenomics referring to the genetic influences on drug response. This field has increasing applications in medicine and clearly holds significant promise for cardiovascular disease management. Awareness of pharmacogenomic advances and the fundamentals of pharmacokinetics and pharmacodynamics can help the clinician more easily deliver great care. Here we attempt to briefly summarize and simplify key concepts of pharmacokinetics, pharmacodynamics, and pharmacogenomics relevant to the cardiovascular disease practitioner.

SLCO1B1 polymorphism is not associated with risk of statin-induced myalgia/myopathy in a Czech population

Background

Gene SLCO1B1, encoding solute organic anionic transport polypeptide OATP1B1, belongs to the group of candidates potentially influencing statin treatment safety. OATP1B1 regulates (not only) the hepatic uptake of statins. Its genetic variation was described as an important predictor of statin-associated myopathy in a cohort of patients treated with a maximum dose of simvastatin. However, the impact of SLCO1B1 gene polymorphism on this risk in patients treated with other statins or lower doses of simvastatin needs to be assessed. Therefore, we performed the present study.

Material/Methods

SLCO1B1 tagging rs4363657 polymorphism was analyzed in 2 groups of patients with dyslipidemia (treated with simvastatin or atorvastatin, 10 or 20 mg per day), subgroup with statin-induced myalgia (N=286), and subgroup (N=707) without myalgia/myopathy, and in 2301 population controls without lipid-lowering treatment.

Results

Frequency of the individual genotypes in patients with myalgia/myopathy (TT=62.3%, CT=34.5%, CC=2.8%) did not significantly differ (both P values over 0.19) from that in patients without muscle symptoms (TT=61.4%, CT=32.9%, CC=5.7%) or from the population controls (TT=63.9%, CT=32.5%, CC=3.6%). Null results were also obtained for the dominant and recessive models of the analysis.

Conclusions

In Czech patients treated with low statin doses, there is no association between SLCO1B1 gene polymorphism and risk of myalgia/myopathy.

Association between SLCO1B1 521 T＞C and 388 A＞G Polymorphisms and Statins Effectiveness: A Meta-Analysis

AIM

Previous studies on the association between the SLCO1B1 521 T＞C and 388 A＞G polymorphisms and statin effectiveness have been inconsistent. We performed this meta-analysis to provide a more comprehensive estimation of this issue.

METHODS

Multiple electronic literatues databases were searched on March 5th 2014. A quality assessment was performed using the Methodological Index for Non-Randomized Studies (MINORS) criteria. A meta-analysis, sub-group analysis, sensitivity analysis (RevMan 5.2), publication bias measuring and meta-regression analysis were conducted utilizing the Stata software program (version 12.0).

RESULTS

A total of 13 studies were included in the final meta-analysis, which included 7,079 participants. Overall, there was no statistically significant association in the four genetic models of hypolipidemic effect. For the 521 T＞C polymorphism, significant associations were found for the long-term effectiveness of lowering the low-density lipoprotein cholesterol (LDL-C) and in non-Asian populations in the dominant model [(CC＋TC vs. TT: mean difference (MD)=1.44, 95% CI: 0.25-2.64,p=0.02) and (CC＋TC vs. TT: MD=1.38, 95% CI: 0.28-2.49, p=0.01)], the recessive model [(CC vs. TT＋TC: MD=3.31, 95% CI: 0.09-6.54, p=0.04) and (CC vs. TT＋TC: MD=2.83, 95% CI: 0.26-5.41, p=0.03)], and the homozygote comparison [(CC vs. TT: MD=3.68, 95% CI: 0.42-6.94,p=0.03) and (CC vs. TT: MD=3.33, 95% CI: 0.67-5.99, p=0.01)], respectively. There were no significant differences for the other analyses of the 521 T＞C polymorphism or all the analyses of the 388 A＞G polymorphism.

CONCLUSIONS

The overall results suggest that the SLCO1B1 521 T＞C and 388 A＞G polymorphisms do not affect the lipid-lowering effectiveness of statins. However, allele C of the SLCO1B1 521 T＞C polymorphism leads to an attenuated effect on lowering the LDL-C in non-Asian populations and the long-term effectiveness of statin treatment.

Genetic and immunologic susceptibility to statin-related myopathy

Statin-related myopathy (SRM) undermines drug adherence that is critical for achieving the benefits of lipid-lowering therapy. While the exact mechanism of SRM remains largely unknown, recent evidence supports specific genetic and immunologic influence on the development of intolerance. Genes of interest include those involved in the pharmacokinetics of statin response (i.e. drug metabolism, uptake transporters, and efflux transporters), pharmacodynamics (i.e. drug toxicity and immune-mediated myopathy), and gene expression. We examine the influence of genetic and immunologic variation on the pharmacokinetics, pharmacodynamics, and gene expression of SRM.

Lipid-lowering efficacy of atorvastatin

BACKGROUND

This represents the first update of this review, which was published in 2012. Atorvastatin is one of the most widely prescribed drugs and the most widely prescribed statin in the world. It is therefore important to know the dose-related magnitude of effect of atorvastatin on blood lipids.

OBJECTIVES

Primary objective To quantify the effects of various doses of atorvastatin on serum total cholesterol, low-density lipoprotein (LDL)-cholesterol, high-density lipoprotein (HDL)-cholesterol and triglycerides in individuals with and without evidence of cardiovascular disease. The primary focus of this review was determination of the mean per cent change from baseline of LDL-cholesterol. Secondary objectives • To quantify the variability of effects of various doses of atorvastatin.• To quantify withdrawals due to adverse effects (WDAEs) in placebo-controlled randomised controlled trials (RCTs).

SEARCH METHODS

We searched the Cochrane Central Register of Controlled Trials (CENTRAL) (Issue 11, 2013), MEDLINE (1966 to December Week 2 2013), EMBASE (1980 to December Week 2 2013), Web of Science (1899 to December Week 2 2013) and BIOSIS Previews (1969 to December Week 2 2013). We applied no language restrictions.

SELECTION CRITERIA

Randomised controlled and uncontrolled before-and-after trials evaluating the dose response of different fixed doses of atorvastatin on blood lipids over a duration of three to 12 weeks.

DATA COLLECTION AND ANALYSIS

Two review authors independently assessed eligibility criteria for studies to be included and extracted data. We collected information on withdrawals due to adverse effects from placebo-controlled trials.

MAIN RESULTS

In this update, we found an additional 42 trials and added them to the original 254 studies. The update consists of 296 trials that evaluated dose-related efficacy of atorvastatin in 38,817 participants. Included are 242 before-and-after trials and 54 placebo-controlled RCTs. Log dose-response data from both trial designs revealed linear dose-related effects on blood total cholesterol, LDL-cholesterol, HDL-cholesterol and triglycerides. The Summary of findings table 1 documents the effect of atorvastatin on LDL-cholesterol over the dose range of 10 to 80 mg/d, which is the range for which this systematic review acquired the greatest quantity of data. Over this range, blood LDL-cholesterol is decreased by 37.1% to 51.7% (Summary of findings table 1). The slope of dose-related effects on cholesterol and LDL-cholesterol was similar for atorvastatin and rosuvastatin, but rosuvastatin is about three-fold more potent. Subgroup analyses suggested that the atorvastatin effect was greater in females than in males and was greater in non-familial than in familial hypercholesterolaemia. Risk of bias for the outcome of withdrawals due to adverse effects (WDAEs) was high, but the mostly unclear risk of bias was judged unlikely to affect lipid measurements. Withdrawals due to adverse effects were not statistically significantly different between atorvastatin and placebo groups in these short-term trials (risk ratio 0.98, 95% confidence interval 0.68 to 1.40).

AUTHORS' CONCLUSIONS

This update resulted in no change to the main conclusions of the review but significantly increases the strength of the evidence. Studies show that atorvastatin decreases blood total cholesterol and LDL-cholesterol in a linear dose-related manner over the commonly prescribed dose range. New findings include that atorvastatin is more than three-fold less potent than rosuvastatin, and that the cholesterol-lowering effects of atorvastatin are greater in females than in males and greater in non-familial than in familial hypercholesterolaemia. This review update does not provide a good estimate of the incidence of harms associated with atorvastatin because included trials were of short duration and adverse effects were not reported in 37% of placebo-controlled trials.

Cardiovascular drugs and the genetic response

The emergence of personalized medicine mandates a complete understating of DNA sequence variation that modulates drug response. Initial forays have been made in the cardiac arena, yet much remains to be elucidated in the pharmacogenetics of cardiac drugs. Most progress has been made in describing DNA sequence variation related to the anticoagulant warfarin and the antiplatelet drug clopidogrel. This includes a description of DNA sequence variation that underlies pharmacokinetic and pharmacodynamic variability, the impact of such variation on predicting hard outcomes, and the ability of genotype-guided prescription to facilitate rapid titration to a therapeutic range while avoiding unnecessary high plasma levels. Nuanced prescription will require a complete inventory of DNA sequence variants that underlie drug-related side effects.

Electronic health records for biological sample collection: feasibility study of statin-induced myopathy using the Clinical Practice Research Datalink

AIMS

Electronic healthcare records (EHRs) are increasingly used to store clinical information. A secondary benefit of EHRs is their use, in an anonymized form, for observational research. The Clinical Practice Research Datalink (CPRD) contains EHRs from primary care in the UK and, despite 1083 peer-reviewed research publications, has never been used to obtain pharmacogenetic samples. Using a statin-induced myopathy paradigm, we evaluated using the CPRD to obtain patient samples for a pharmacogenetic study targeting 250 cases and 500 controls from UK general practitioner (GP) practices.

METHODS

The CPRD identified potential patients fitting specific case-definition criteria (active rhabdomyolysis or creatine phosphokinase > four times the upper limit of normal), and corresponding GP practices were asked to invite patient participation. Consenting patients were requested to provide either saliva or blood samples and to complete an ethnicity questionnaire. Control subjects were recruited from the same GP practice (saliva) or a small number of practices (blood). Samples were forwarded for DNA extraction.

RESULTS

Thirty-six months of recruitment yielded DNA samples from 149 statin-induced myopathy cases and 587 tolerant controls. Data show that contacting patients through their GP is a reliable method for obtaining samples without compromising anonymity. Saliva collection directly from patients was considerably less effective than blood sampling. After 10 months of recruitment, saliva sampling was suspended in favour of blood sampling.

CONCLUSIONS

We demonstrate the potential of EHRs for identifying accurately phenotyped cases and controls for pharmacogenetic studies. Recruitment was successful only because of the willingness of GP practices to participate and the existence of strong doctor–patient relationships. The present study provides a model that can be implemented in future genetic analyses using EHRs.

The Interaction Between Statins and Exercise: Mechanisms and Strategies to Counter the Musculoskeletal Side Effects of This Combination Therapy

BACKGROUND

Broad indications for the use of statin medications are resulting in more patients using these therapies. Simultaneously, healthcare professionals are strongly advocating recommendations to increase exercise training (ET) as a means of decreasing cardiovascular disease (CVD) risk and improving other parameters of fitness.

METHODS

We review the literature to explore mechanisms that may increase the risk of statin/ET interactions, examine the benefits and risks of combining ET and statin use, and offer strategies to minimize the hazards of this combination therapy.

RESULTS

The combined use of statins and ET can result in health gains and decreased CVD risk; however, multiple factors may increase the risk of adverse events. Some of the events that have been reported with the combination of statins and ET include decreased athletic performance, muscle injury, myalgia, joint problems, decreased muscle strength, and fatigue. The type of statin, the dose, drug interactions, genetic variants, coenzyme Q10 deficiency, vitamin D deficiency, and underlying muscle diseases are among the factors that may predispose patients to intolerance of this combined therapy.

CONCLUSION

Effective strategies exist to help patients who may be intolerant of combined statin therapy and ET so they may benefit from this proven therapy. Careful attention to identifying high-risk groups and strategies to prevent or treat side effects that may occur should be employed.

What do drug transporters really do?

Potential drug-drug interactions mediated by the ATP-binding cassette (ABC) transporter and solute carrier (SLC) transporter families are of clinical and regulatory concern. However, the endogenous functions of these drug transporters are not well understood. Discussed here is evidence for the roles of ABC and SLC transporters in the handling of diverse substrates, including metabolites, antioxidants, signalling molecules, hormones, nutrients and neurotransmitters. It is suggested that these transporters may be part of a larger system of remote communication ('remote sensing and signalling') between cells, organs, body fluid compartments and perhaps even separate organisms. This broader view may help to clarify disease mechanisms, drug-metabolite interactions and drug effects relevant to diabetes, chronic kidney disease, metabolic syndrome, hypertension, gout, liver disease, neuropsychiatric disorders, inflammatory syndromes and organ injury, as well as prenatal and postnatal development.

Pharmacogenomics of statin therapy: any new insights in efficacy or safety?

PURPOSE OF REVIEW

To examine the current evidence concerning the effects of genetic variation on statin-related low-density lipoprotein cholesterol reductions, clinical efficacy, and adverse events and the relevance for patient care.

RECENT FINDINGS

Recent years have seen the emergence of large-scale genetic experiments, including genome-wide association studies and candidate gene studies, exploring the impact of common genetic variation on patient response to statins. These studies have built on previous smaller scale evidence, providing improved statistical power and enhanced ability to explore the genome. Current evidence suggests that common genetic variants do not alter low-density lipoprotein cholesterol response by more than a few percent, or materially alter the effect of statin on vascular risk reduction, and therefore that patients benefit from statins independent of common genetic variation. However, knowledge of SLCO1B1 genotypes is believed to have clinical utility for predicting myopathy risk and ensuring that statins are prescribed as safely as possible. Furthermore, new hypothesis-generating studies, such as those associating GATM with myopathy risk, offer potential insights for the future.

SUMMARY

Common genetic variation does not appear to be an important determinant of statin response, with the exception of SLCO1B1 and risk of myopathy. Future studies will help to determine the impact of low-frequency and rare genetic variation on statin response.

Genetic variation in the UGT1A locus is associated with simvastatin efficacy in a clinical practice setting

Aim: Simvastatin is a lactone prodrug that exists in equilibrium with its active hydroxyacid through a process mediated by UGT1A enzymes. The UGT1A locus has been associated with simvastatin response and disposition in humans. Therefore, we fine-mapped the UGT1A locus to identify genetic variations contributing to simvastatin disposition and response variability. Methods: Using de-identified electronic medical records linked to a DNA biobank, we extracted information about dose and low-density lipo-protein cholesterol (LDL-C) concentrations for patients who received more than two different doses of simvastatin. Pharmacodynamic measures of simvastatin potency and efficacy were calculated from dose-response curves (E0 = baseline LDL-C, ED50 = dose yielding 50% maximum response, and Emax = maximum decrease in LDL-C) in 1100 patients. We selected 153 polymorphisms in UGT1A1 and UGT1A3 for genotyping and conducted genotype-phenotype associations using a prespecified additive model. Results: Two variants in UGT1A1 (rs2003569 and rs12052787) were associated with Emax (p = 0.0059 and 0.031, respectively; for rs2003569 the mean Emax was 59.3 ± 23.0, 62.0 ± 22.4, and 69.7 ± 24.8 mg/dl, for patients with 0, 1 or 2 copies of the minor A allele, respectively). When stratified by race, the difference in response was greater in African-Americans than in European Americans. Rs2003569 was also negatively associated with total serum bilirubin levels (p = 7.85 × 10-5). Four rare SNPs were nominally associated with E0 and ED50. Conclusion: We identified a UGT1A1 promoter variant (rs2003569) associated with simvastatin efficacy. Original submitted 26 March 2014; Revision submitted 26 August 2014.

How drugs get into cells: tested and testable predictions to help discriminate between transporter-mediated uptake and lipoidal bilayer diffusion

One approach to experimental science involves creating hypotheses, then testing them by varying one or more independent variables, and assessing the effects of this variation on the processes of interest. We use this strategy to compare the intellectual status and available evidence for two models or views of mechanisms of transmembrane drug transport into intact biological cells. One (BDII) asserts that lipoidal phospholipid Bilayer Diffusion Is Important, while a second (PBIN) proposes that in normal intact cells Phospholipid Bilayer diffusion Is Negligible (i.e., may be neglected quantitatively), because evolution selected against it, and with transmembrane drug transport being effected by genetically encoded proteinaceous carriers or pores, whose “natural” biological roles, and substrates are based in intermediary metabolism. Despite a recent review elsewhere, we can find no evidence able to support BDII as we can find no experiments in intact cells in which phospholipid bilayer diffusion was either varied independently or measured directly (although there are many papers where it was inferred by seeing a covariation of other dependent variables). By contrast, we find an abundance of evidence showing cases in which changes in the activities of named and genetically identified transporters led to measurable changes in the rate or extent of drug uptake. PBIN also has considerable predictive power, and accounts readily for the large differences in drug uptake between tissues, cells and species, in accounting for the metabolite-likeness of marketed drugs, in pharmacogenomics, and in providing a straightforward explanation for the late-stage appearance of toxicity and of lack of efficacy during drug discovery programmes despite macroscopically adequate pharmacokinetics. Consequently, the view that Phospholipid Bilayer diffusion Is Negligible (PBIN) provides a starting hypothesis for assessing cellular drug uptake that is much better supported by the available evidence, and is both more productive and more predictive.

The clinical pharmacogenetics implementation consortium guideline for SLCO1B1 and simvastatin-induced myopathy: 2014 update

Simvastatin is among the most commonly used prescription medications for cholesterol reduction. A single coding single-nucleotide polymorphism, rs4149056T>C, in SLCO1B1 increases systemic exposure to simvastatin and the risk of muscle toxicity. We summarize evidence from the literature supporting this association and provide therapeutic recommendations for simvastatin based on SLCO1B1 genotype. This article is an update to the 2012 Clinical Pharmacogenetics Implementation Consortium guideline for SLCO1B1 and simvastatin-induced myopathy.

Phenotype standardization for statin-induced myotoxicity

Statins are widely used lipid-lowering drugs that are effective in reducing cardiovascular disease risk. Although they are generally well tolerated, they can cause muscle toxicity, which can lead to severe rhabdomyolysis. Research in this area has been hampered to some extent by the lack of standardized nomenclature and phenotypic definitions. We have used numerical and descriptive classifications and developed an algorithm to define statin-related myotoxicity phenotypes, including myalgia, myopathy, rhabdomyolysis, and necrotizing autoimmune myopathy.

Personalized genomes and cardiovascular disease

The emerging ability to obtain a personalized genome, that is, to perform whole-genome sequencing to determine the entirety of the DNA sequence in an individual patient's chromosomes, holds out the promise of transforming patient care by allowing physicians to more accurately predict the risk of disease and to tailor therapy to that individual. Although no established applications of personalized genomics in cardiovascular medicine yet exist, there are at least two emerging applications that may ultimately become everyday practice. In the first application, DNA sequence variants that have been found to be associated with cardiovascular disease may be incorporated in risk-prediction algorithms to more accurately forecast whether patients will develop disease. In the second application, known as pharmacogenomics, DNA sequence variants that have been found to be associated with either beneficial effects or adverse effects of a medication may be used to help decide which medications or dosages of medications to prescribe to patients. It remains to be seen whether either of these applications will prove to be both cost effective as well as of clinical benefit.

Uremic toxins enhance statin-induced cytotoxicity in differentiated human rhabdomyosarcoma cells

The risk of myopathy and rhabdomyolysis is considerably increased in statin users with end-stage renal failure (ESRF). Uremic toxins, which accumulate in patients with ESRF, exert cytotoxic effects that are mediated by various mechanisms. Therefore, accumulation of uremic toxins might increase statin-induced cytotoxicity. The purpose of this study was to determine the effect of four uremic toxins-hippuric acid, 3-carboxy-4-methyl-5-propyl-2-furanpropionate, indole-3-acetic acid, and 3-indoxyl sulfate-on statin-induced myopathy. Differentiated rhabdomyosarcoma cells were pre-treated with the uremic toxins for seven days, and then the cells were treated with pravastatin or simvastatin. Cell viability and apoptosis were assessed by viability assays and flow cytometry. Pre-treatment with uremic toxins increased statin- but not cisplatin-induced cytotoxicity (p < 0.05 vs. untreated). In addition, the pre-treatment increased statin-induced apoptosis, which is one of the cytotoxic factors (p < 0.05 vs. untreated). However, mevalonate, farnesol, and geranylgeraniol reversed the effects of uremic toxins and lowered statin-induced cytotoxicity (p < 0.05 vs. untreated). These results demonstrate that uremic toxins enhance statin-induced apoptosis and cytotoxicity. The mechanism underlying this effect might be associated with small G-protein geranylgeranylation. In conclusion, the increased severity of statin-induced rhabdomyolysis in patients with ESRF is likely due to the accumulation of uremic toxins.

Mechanisms and assessment of statin-related muscular adverse effects

Statin-associated muscular adverse effects cover a wide range of symptoms, including asymptomatic increase of creatine kinase serum activity and life-threatening rhabdomyolysis. Different underlying pathomechanisms have been proposed. However, a unifying concept of the pathogenesis of statin-related muscular adverse effects has not emerged so far. In this review, we attempt to categorize these mechanisms along three levels. Firstly, among pharmacokinetic factors, it has been shown for some statins that inhibition of cytochrome P450-mediated hepatic biotransformation and hepatic uptake by transporter proteins contribute to an increase of systemic statin concentrations. Secondly, at the myocyte membrane level, cell membrane uptake transporters affect intracellular statin concentrations. Thirdly, at the intracellular level, inhibition of the 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase results in decreased intracellular concentrations of downstream metabolites (e.g. selenoproteins, ubiquinone, cholesterol) and alteration of gene expression (e.g. ryanodine receptor 3, glycine amidinotransferase). We also review current recommendations for prescribers.

Safety of statins: an update

Statins are widely used and have been proven to be effective in the prevention of atherosclerotic vascular disease events, primarily by reducing plasma low-density lipoprotein cholesterol concentrations. Although statins are generally well tolerated and present an excellent safety profile, adverse effects from muscle toxicity and liver enzyme abnormalities may occur in some patients. Myopathy and rhabdomyolysis are rare with statin monotherapy at the approved dose ranges, but the risk increases with use of higher doses, interacting drugs and genetic predisposition. Asymptomatic increases in liver transaminases with statin treatment do not seem to be associated with an increased risk of liver disease. Therefore, statin treatment can be safely used in patients with mild to moderately abnormal liver tests that are potentially attributable to nonalcoholic fatty liver disease and can improve liver tests and reduce cardiovascular morbidity in this group of patients. The risks of other unfavorable effects such as the slightly increased risk of new-onset diabetes and potentially increased risk of haemorrhagic stroke are much smaller than the cardiovascular benefits with the use of statins.

Non-cardiovascular effects associated with statins

Statins form the pharmacologic cornerstone of the primary and secondary prevention of atherosclerotic cardiovascular disease. In addition to beneficial cardiovascular effects, statins seem to have multiple non-cardiovascular effects. Although early concerns about statin induced hepatotoxicity and cancer have subsided owing to reassuring evidence, two of the most common concerns that clinicians have are myopathy and diabetes. Randomized controlled trials suggest that statins are associated with a modest increase in the risk of myositis but not the risk of myalgia. Severe myopathy (rhabdomyolysis) is rare and often linked to a statin regimen that is no longer recommended (simvastatin 80 mg). Randomized controlled trials and meta-analyses suggest an increase in the risk of diabetes with statins, particularly with higher intensity regimens in people with two or more components of the metabolic syndrome. Other non-cardiovascular effects covered in this review are contrast induced nephropathy, cognition, cataracts, erectile dysfunction, and venous thromboembolism. Currently, systematic reviews and clinical practice guidelines indicate that the cardiovascular benefits of statins generally outweigh non-cardiovascular harms in patients above a certain threshold of cardiovascular risk. Literature is also accumulating on the potential non-cardiovascular benefits of statins, which could lead to novel applications of this class of drug in the future.

Application of a Physiologically Based Pharmacokinetic Model to Predict OATP1B1-Related Variability in Pharmacodynamics of Rosuvastatin

Typically, pharmacokinetic–pharmacodynamic (PK/PD) models use plasma concentration as the input that drives the PD model. However, interindividual variability in uptake transporter activity can lead to variable drug concentrations in plasma without discernible impact on the effect site organ concentration. A physiologically based PK/PD model for rosuvastatin was developed that linked the predicted liver concentration to the PD response model. The model was then applied to predict the effect of genotype-dependent uptake by the organic anion-transporting polypeptide 1B1 (OATP1B1) transporter on the pharmacological response. The area under the plasma concentration–time curve (AUC_0–∞) was increased by 63 and 111% for the c.521TC and c.521CC genotypes vs. the c.521TT genotype, while the PD response remained relatively unchanged (3.1 and 5.8% reduction). Using local concentration at the effect site to drive the PD response enabled us to explain the observed disconnect between the effect of the OATP1B1 c521T>C polymorphism on rosuvastatin plasma concentration and the cholesterol synthesis response.

Synergistic interaction between genetics and disease on pravastatin disposition

BACKGROUND & AIMS

A genome wide association study and multiple pharmacogenetic studies have implicated the hepatic uptake transporter organic anion transporting polypeptide-1B1 (OATP1B1) in the pharmacokinetics and musculoskeletal toxicity of statin drugs. Other OATP uptake transporters can participate in the transport of pravastatin, partially compensating for the loss of OATP1B1 in patients carrying the polymorphism. Non-alcoholic steatohepatitis (NASH) in humans and in a diet-induced rodent model alter the expression of multiple OATP transporters.

METHODS

To determine how genetic alteration in one Oatp transporter can interact with NASH-associated changes in Oatp expression we measured the disposition of intravenously administered pravastatin in Slco1b2 knockout (Slco1b2(-/-)) and wild-type (WT) mice fed either a control or a methionine and choline deficient (MCD) diet to induce NASH.

RESULTS

Genetic loss of Oatp1b2, the rodent ortholog of human OATP1B transporters, caused a modest increase in pravastatin plasma concentrations in mice with healthy livers. Although a diet-induced model of NASH decreased the expression of multiple hepatic Oatp transporters, it did not alter the disposition of pravastatin compared to WT control mice. In contrast, the combination of NASH-associated decrease in compensatory Oatp transporters and Oatp1b2 genetic loss caused a synergistic increase in plasma area under the curve (AUC) and tissue concentrations in kidney and muscle.

CONCLUSIONS

Our data show that NASH alters the expression of multiple hepatic uptake transporters which, due to overlapping substrate specificity among the OATP transporters, may combine with the pharmacogenetic loss of OATP1B1 to increase the risk of statin-induced adverse drug reactions.

How will insights from genetics translate to clinical practice in inflammatory bowel disease?

Inflammatory bowel disease, consisting of Crohn's disease and ulcerative colitis, is a chronic inflammatory disease of the gut, which arises through an excessive immune response to the normal gut flora in a genetically susceptible host. The disease affects predominantly young adults and due to its chronic and relapsing nature gives rise to a high disease burden both financially, physically and psychologically. Current therapy still cannot prevent the need for surgical intervention in more than half of IBD patients. Consequently, advances in IBD therapy are of high importance. Recently, several new forms of targeted therapy have been introduced, which should improve surgery-free prognosis of IBD patients. Recent identification of genetic risk variants for IBD has led to new insights into the biological mechanisms of the disease, which will, in the future, lead to new targeted therapy. In the meantime repositioning of drugs from biologically similar diseases towards IBD might lead to new IBD therapies.

Overcoming toxicity and side-effects of lipid-lowering therapies

Lowering serum lipid levels is part of the foundation of treating and preventing clinically significant cardiovascular disease. Recently, the American Heart Association/American College of Cardiology released cholesterol guidelines which advocate for high efficacy statins rather than LDL-c goals for five patient subgroups at high risk for cardiovascular disease. Therefore, it is critical that clinicians have an approach for managing side-effects of statin therapy. Statins are associated with myopathy, transaminase elevations, and an increased risk of incident diabetes mellitus among some patients; connections between statins and other processes, such as renal and neurologic function, have also been studied with mixed results. Statin-related adverse effects might be minimized by careful assessment of patient risk factors. Strategies to continue statin therapy despite adverse effects include switching to another statin at a lower dose and titrating up, giving intermittent doses of statins, and adding non-statin agents. Non-statin lipid-lowering drugs have their own unique limitations. Management strategies and algorithms for statin-associated toxicities are available to help guide clinicians. Clinical practice should emphasize tailoring therapy to address each individual's cholesterol goals and risk of developing adverse effects on lipid-lowering drugs.

Personalized medicine: importance of clinical interpretative skills for real-world patient care

Sequencing of the human genome led to great hopes and expectations for a 'genomics revolution' where disease diagnosis as well as therapies would be based on an individual's genetic makeup. Although significant progress has been made, a number of challenging hurdles must be overcome prior to the broader adoption and implementation of pharmacogenomics and personalized medicine as a part of standard patient care. One aspect of pharmacogenomics-based personalized medicine that has not garnered as much attention, a key focus of this perspective, is the importance of interpreting pharmacogenomic test results in a patient-specific clinical context, and expert physicians and other allied health care providers with the requisite expertise in clinical pharmacology and genomics who are able to provide such services.

Personalized pharmacogenomics: predicting efficacy and adverse drug reactions

Drug response varies between individuals owing to disease heterogeneity, environmental factors, and genetic factors. Genetic factors can affect both the pharmacokinetics and pharmacodynamics of a drug, leading to changes in local and systemic drug exposure and/or changes in the function of the drug target, altering drug response. Several pharmacogenetic biomarkers are already utilized in clinical practice and have been shown to improve clinical outcomes. However, a large number of other biomarkers have never made it beyond the discovery stage. Concerted effort is needed to improve the translation of pharmacogenetic biomarkers into clinical practice, and this will involve the use of standardized phenotyping and genotyping strategies, collaborative work, multidisciplinary approaches to identifying and replicating associations, and cooperation with industry to facilitate translation and commercialization. Acceptance of these approaches by clinicians, regulators, patients, and the public will be important in determining future success.

Statins and skeletal muscles toxicity: from clinical trials to everyday practice

The mechanism(s) underlying the occurrence of statin-induced myopathy are ill defined, but the results of observational studies and clinical trials provide compelling evidence that skeletal muscle toxicity is a frequent, dose-dependent, adverse event associated with all statins. It has been suggested that reduced availability of metabolites produced by the mevalonate pathway rather than intracellular cholesterol lowering per se might be the primary trigger of toxicity, however other alternative explanations have gained credibility in recent years. Aim of this review is: (i) to describe the molecular mechanisms associated to statin induced myopathy including defects in isoprenoids synthesis followed by altered prenylation of small GTPase, such as Ras and Rab proteins; (ii) to present the emerging aspects on pharmacogenetics, including CYP3A4, OATP1B1 and glycine amidinotransferase (GATM) polymorphisms impacting either statin bioavailability or creatine synthesis; (iii) to summarize the available epidemiological evidences; and (iii) to discuss the concepts that would be of interest to the clinicians for the daily management of patients with statin induced myopathy. The interplay between drug-environment and drug-drug interaction in the context of different genetic settings contribute to statins and skeletal muscles toxicity. Until specific assays/algorithms able to combine genetic scores with drug-drug-environment interaction to identify patients at risk of myopathies will become available, clinicians should continue to monitor carefully patients on polytherapy which include statins and be ready to reconsider dose, statin or switching to alternative treatments. The beneficial effects of adding agents to provide the muscle with the metabolites, such as CoQ10, affected by statin treatment will also be addressed.

Dietary modulators of statin efficacy in cardiovascular disease and cognition

Cardiovascular disease remains the leading cause of morbidity and mortality in the United States and other developed countries, and is fast growing in developing countries, particularly as life expectancy in all parts of the world increases. Current recommendations for the prevention of cardiovascular disease issued jointly from the American Academy of Cardiology and American Heart Association emphasize that lifestyle modification should be incorporated into any treatment plan, including those on statin drugs. However, there is a dearth of data on the interaction between diet and statins with respect to additive, complementary or antagonistic effects. This review collates the available data on the interaction of statins and dietary patterns, cognition, genetics and individual nutrients, including vitamin D, niacin, omega-3 fatty acids, fiber, phytochemicals (polyphenols and stanols) and alcohol. Of note, although the available data is summarized, the scope is limited, conflicting and disparate. In some cases it is likely there is unrecognized synergism. Virtually no data are available describing the interactions of statins with dietary components or dietary pattern in subgroups of the population, particularly those who may benefit most were positive effects identified. Hence, it is virtually impossible to draw any firm conclusions at this time. Nevertheless, this area is important because were the effects of statins and diet additive or synergistic harnessing the effect could potentially lead to the use of a lower intensity statin or dose.

Genetic factors affecting statin concentrations and subsequent myopathy: a HuGENet systematic review

Statins, 3-hydroxy-3-methyl-glutaryl-coenzyme A reductase inhibitors, have proven efficacy in both lowering low-density-lipoprotein levels and preventing major coronary events, making them one of the most commonly prescribed drugs in the United States. Statins exhibit a class-wide side effect of muscle toxicity and weakness, which has led regulators to impose both dosage limitations and a recall. This review focuses on the best-characterized genetic factors associated with increased statin muscle concentrations, including the genes encoding cytochrome P450 enzymes (CYP2D6, CYP3A4, and CYP3A5), a mitochondrial enzyme (GATM), an influx transporter (SLCO1B1), and efflux transporters (ABCB1 and ABCG2). A systematic literature review was conducted to identify relevant research evaluating the significance of genetic variants predictive of altered statin concentrations and subsequent statin-related myopathy. Studies eligible for inclusion must have incorporated genotype information and must have associated it with some measure of myopathy, either creatine kinase levels or self-reported muscle aches and pains. After an initial review, focus was placed on seven genes that were adequately characterized to provide a substantive review: CYP2D6, CYP3A4, CYP3A5, GATM, SLCO1B1, ABCB1, and ABCG2. All statins were included in this review. Among the genetic factors evaluated, statin-related myopathy appears to be most strongly associated with variants in SLCO1B1.

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.