Genetic determinants of response to statins

Approach to the Patient With a Suboptimal Statin Response: Causes and Algorithm for Clinical Management

CONTEXT

Statins are the lipid-lowering therapy of choice for the prevention of atherosclerotic cardiovascular disease (ASCVD) but their effectiveness in lowering low-density lipoprotein cholesterol (LDL-C) can substantially differ between individuals. In this mini-review, we describe the different causes for a suboptimal statin response and an algorithm for the diagnosis and clinical management of these patients.

EVIDENCE ACQUISITION

A PubMed search using the terms "statin resistance," "statin sensitivity," "statin pharmacokinetics," "cardiovascular disease," and "lipid-lowering therapies" was performed. Published papers in the past 10 years that were relevant to the topic were examined to provide content for this mini-review.

EVIDENCE SYNTHESIS

Suboptimal lowering of LDL-C by statins is a major problem in the clinical management of patients and limits the value of this therapeutic approach. There are multiple causes of statin hyporesponsiveness with compliance being the most common explanation. Other causes, such as analytical issues with LDL-C measurement and the presence of common lipid disorders (familial hypercholesterolemia, elevated lipoprotein[a] and secondary dyslipidemias) should be excluded before considering primary statin resistance from rare genetic variants in lipoprotein-related or drug-metabolism genes. A wide variety of nonstatin lipid-lowering drugs are now available and can be added to statins to achieve more effective LDL-C lowering.

CONCLUSIONS

The evaluation of statin hyporesponsiveness is a multistep process that can lead to the optimization of lipid-lowering therapy for the prevention of ASCVD. It may also lead to the identification of distinct types of dyslipidemias that require specific therapies and/or the genetic screening of family members.

Effects of lowest-dose vs. highest-dose pitavastatin on coronary neointimal hyperplasia at 12-month follow-up in type 2 diabetic patients with non-ST elevation acute coronary syndrome: an optical coherence tomography analysis

Current ACC/AHA guidelines recommend high-dose statin therapy after coronary stenting, especially in diabetic patients; however, pitavastatin 4 mg or pitavastatin 1 mg are frequently used after coronary stenting in Asia, even in patients with acute coronary syndrome. We compared the effects of highest-dose and lowest-dose pitavastatin therapy on coronary neointimal hyperplasia at 12-month follow-up in diabetic patients with non-ST-elevation acute coronary syndrome (NSTE-ACS) using optical coherence tomography. A total of 72 diabetic patients with NSTE-ACS were randomized to lowest-dose pitavastatin [1 mg (n = 36)] or highest-dose pitavastatin [4 mg (n = 36)] after everolimus-eluting stent implantation. The primary endpoint was to compare the normalized neointimal volume at 12-month follow-up. Normalized neointimal volume was significantly lower in the pitavastatin 4 mg group (4.00 ± 2.80 vs. 8.24 ± 2.83 mm³/mm, p < 0.01) at 12-month follow-up. There was also significant difference in neointimal area between the pitavastatin 4 mg group and pitavastatin 1 mg group (0.41 ± 0.28 vs. 0.74 ± 0.23 mm², p < 0.01). Improvement of brachial artery flow-mediated dilation (baFMD) was significantly higher in the pitavastatin 4 mg group than in pitavastatin 1 mg group (0.15 ± 0.15 vs. - 0.03 ± 0.19 mm, p < 0.001). In addition, the improvement of adiponectin levels was significantly greater in the pitavastatin 4 mg group than in the pitavastatin 1 mg group (2.97 ± 3.98 vs. 0.59 ± 2.80 μg/mL, p < 0.05). Pitavastatin 4 mg significantly improved inflammatory cytokines and lipid profiles compared to pitavastatin 1 mg during the 12-month follow-up, contributing to the reduction of neointimal hyperplasia and to the improvement of baFMD in diabetic patients with NSTE-ACS requiring coronary stenting. Thus, the administration of pitavastatin 4 mg can be safely and effectively used in high-risk patients requiring coronary stenting. Trial registration NCT02545231 (Clinical Trial registration information: https://clinicaltrials.gov/ct2/show/NCT02545231 ).

Molecular mechanisms of statin intolerance

Statins reduce cardiovascular morbidity and mortality in primary and secondary prevention. Despite their efficacy, many persons are unable to tolerate statins due to adverse events such as hepatotoxicity and myalgia/myopathy. In the case of most patients, it seems that mild-to-moderate abnormalities in liver and muscle enzymes are not serious adverse effects and do not outweigh the benefits of coronary heart disease risk reduction. The risk for mortality or permanent organ damage ascribed to statin use is very small and limited to cases of myopathy and rhabdomyolysis. Statin-induced muscle-related adverse events comprise a highly heterogeneous clinical disorder with numerous, complex etiologies and a variety of genetic backgrounds. Every patient who presents with statin-related side effects cannot undergo the type of exhaustive molecular characterization that would include all of these mechanisms. Frequently the only solution is to either discontinue statin therapy/reduce the dose or attempt intermittent dosing strategies at a low dose.

Prevalence of genetic variants associated with cardiovascular disease risk and drug response in the Southern Indian population of Kerala

BACKGROUND AND AIM:

This study reports the prevalence of five clinically significant variants associated with increased risk of cardiovascular disorders, and variable responses of individuals to commonly prescribed cardiovascular drugs in a South Indian population from the state of Kerala.

MATERIALS AND METHODS:

Genomic DNA isolated from 100 out-patient samples from Kerala were sequenced to examine the frequency of clinically relevant polymorphisms in the genes MYBPC3 (cardiomyopathy), SLCO1B1 (statin-induced myopathy), CYP2C9, VKORC1 (response to warfarin) and CYP2C19 (response to clopidogrel).

RESULTS:

Our analyses revealed the frequency of a 25 bp deletion variant of MYBPC3 associated with risk of cardiomyopathy was 7%, and the SLCO1B1 “C” allele associated with risk for statin-induced myopathy was 15% in this sample group. Among the other variants associated with dose-induced toxicity of warfarin, VKORC1 (c.1639G>A), was detected at 22%, while CYP2C9*3 and CYP2C9*2 alleles were present at a frequency of 15% and 3% respectively. Significantly, the tested sample population showed high prevalence (66%) of CYP2C19*2 variant, which determines response to clopidogrel therapy.

CONCLUSIONS:

We have identified that certain variants associated with cardiovascular disease and related drug response in the five genes, especially those in VKORC1, CYP2C19 and MYBPC3, are highly prevalent in the Kerala population, with almost 2 times higher prevalence of CYP2C19*2 variant compared with other regions in the country. Since the variants chosen in this study have relevance in disease phenotype and/or drug response, and are detected at a higher frequency, this study is likely to encourage clinicians to perform genetic testing before prescribing therapy.

Pharmacogenetics in cardiovascular disease: the challenge of moving from promise to realization: concepts discussed at the Canadian Network and Centre for Trials Internationally Network Conference (CANNeCTIN), June 2009

Pharmacogenetics in cardiovascular medicine brings the potential for personalized therapeutic strategies that improve efficacy and reduce harm. Studies evaluating the impact of genetic variation on pharmacologic effects have been undertaken for most major cardiovascular drugs, including antithrombotic agents, β-adrenergic receptor blockers, statins, and angiotensin-converting enzyme inhibitors. Across these drug classes, many polymorphisms associated with pharmacodynamic, pharmacokinetic, or surrogate outcomes have been identified. However, their impact on clinical outcomes and their ability to improve clinical practice remains unclear. This review will examine the current clinical evidence supporting pharmacogenetic testing in cardiovascular medicine, provide clinical guidance based on the current evidence, and identify further steps needed to determine the utility of pharmacogenetics in cardiovascular care.

Systemic exposure to atorvastatin between Asian and Caucasian subjects: a combined analysis of 22 studies

The aim of the present study was to determine whether there is a differing pattern of systemic exposure to atorvastatin in Asian versus Caucasian subjects by comparison of data obtained from completed pharmacokinetic studies. Pharmacokinetic data were analyzed from completed single-dose (10-80 mg) studies in Asian and Caucasian subjects. Dose normalized area under the concentration-time curve (AUC) and maximum observed concentration (Cmax) (AUC(dn) and Cmax(dn)) were obtained by dividing each value by the administered dose. Dose-per-bodyweight normalized AUC and Cmax (AUC(dn,wt) and Cmax,(dn,wt)) were obtained by dividing each value by the administered dose per unit bodyweight. Mean difference and 90% confidence intervals for Asian versus Caucasian comparisons were calculated for atorvastatin pharmacokinetic values based on the t statistic and expressed as ratios using Caucasians as the reference. Data were analyzed from 310 Asians and 579 Caucasians from 22 studies. AUC(dn) (Asian = 2.35, Caucasian = 2.06 [ng·hr·mL(-1)]/mg) and Cmax(dn) (Asian = 0.39, Caucasian = 0.40 Cmax(dn,wt)) and the equivalent dose-per-bodyweight normalized values for atorvastatin (AUC(dn,wt): Asian = 157.5, Caucasian = 156.4 [ng·hr·mL(-1)]/[mg·kg(-1)]; Cmax(dn,wt): Asian = 26.2, Caucasian = 30.3 [ng·mL(-1)]/[mg·kg(-1)]) were similar in both ethnic groups. Mean differences and 90% confidence interval for the differences fell within the limits (0.8-1.25) except for Cmax(dn,wt), for which the lower limit was slightly below 80%. No differences were noted in the systemic exposure to atorvastatin between Asian and Caucasian subjects. These data therefore demonstrate that dosing considerations in the current labels for atorvastatin are similar for Asian compared with Caucasian subjects.

Genetic variability within the cholesterol lowering pathway and the effectiveness of statins in reducing the risk of MI

Genetic variability has been shown to affect statin responsiveness. Participants from the Utrecht Cardiovascular Pharmacogenetics (UCP) studies were enrolled from a population-based registry of pharmacy records linked to hospital discharge records (PHARMO) to investigate tagging SNPs within candidate genes involved in the cholesterol lowering pathway for modification of the effectiveness of statins in reducing the risk of myocardial infarction (MI). Patients who received a prescription for an antihypertensive drug and/or had hypercholesterolemia were selected from the PHARMO database. We designed a nested case-control study in which cases were hospitalized for MI and controls were not. Patients were contacted through their community pharmacies. For this study, only hypercholesterolemic participants were selected. Logistic regression analysis was used to investigate pharmacogenetic interactions. The Heart and Vascular Health Study (HVH) was used to replicate findings from UCP. The study population included 668 cases and 1217 controls. We selected 231 SNPs of which 209 SNPs in 27 genes passed quality control. Ten SNPs in eight genes were found to influence the effectiveness of statins in UCP, of which the most significant interaction was found with SCARB1 rs4765615. Other genes that reached statistical significance (p<0.05) included two SNPs in PCSK9 (rs10888896 and rs505151 (E670G)), two SNPs in ABCG5 (rs4245786 and rs1864815), LIPC rs16940379, ABCA1 rs4149264, PPARG rs2972164, LRP1 rs715948, and SOAT1 rs2493121. None of the total of 5 SNPs that were available for replication in HVH reached statistical significance. In conclusion, ten SNPs were found to modify the effectiveness of statins in reducing the risk of MI in the UCP study. Five were also tested in the HVH study, but no interactions reached statistical significance.

Pharmacogenetic interactions between ABCB1 and SLCO1B1 tagging SNPs and the effectiveness of statins in the prevention of myocardial infarction

AIMS

Genetic variability within the SLCO1B1 and ABCB1 transporter genes has been associated with modification of statin effectiveness in cholesterol management.

MATERIALS & METHODS

We conducted a case-control study using a population-based registry of pharmacy records linked to the hospital discharge records. Within a hypercholesterolemic cohort, we included 668 myocardial infarction cases and 1217 controls.

RESULTS

We tested 24 tagging SNPs and found two SNPs within ABCB1 (rs3789244, p = 0.01; rs1922242, p = 0.01) to interact with statin treatment. In addition, we found a nonsignificant haplotype-treatment interaction (p = 0.054). The odds ratio for subjects homozygous for SLCO1B1*1A was 0.49 (95% CI: 0.34-0.71) compared with 0.31 (95% CI: 0.24-0.41) for heterozygous or noncarriers of the *1A allele.

CONCLUSION

This is the first study to demonstrate that common genetic variability within the SLCO1B1 and ABCB1 genes is associated with the modification of the effectiveness of statins in the prevention of the clinical outcome, myocardial infarction.

Common sequence variants in pharmacodynamic and pharmacokinetic pathway-related genes conferring LDL cholesterol response to statins

AIMS

This study assessed the association between pharmacokinetic- and pharmacodynamic-related genes and individual responses to low-density lipoprotein cholesterol (LDL-C) change by statins in a Chinese population.

MATERIALS & METHODS

A total of 386 patients with primary hypercholesterolemia were treated with statins for 9 months. The 62 haplotype-tagging SNPs of ten candidate genes were genotyped. Treating LDL-C reduction as an outcome variable, we performed multiple linear regression models in various modes of inheritance to test the effects of SNP and haplotype variants.

RESULTS

After correction for the multiple tests, only rs12916 in HMGCR and rs9902941 in SREBF1 remained significant. For rs12916 in the HMGCR gene, individuals with CC genotype showed a reduction of 56.9 mg/dl for LDL-C, with the reduction increasing to 60.1 and 62.5 mg/dl among individuals carrying CT and TT, respectively (p-value for additive model = 0.006). For the HMGCR gene, subjects carrying the CCGTCCA haplotype had a significant increase of LDL-C (adjusted mean -7.2 +/- 2.3 mg/dl; p-value for global test = 0.002). For the ABCG8 gene, subjects carrying the ATTATCGAC haplotype had a significant reduction of LDL-C (adjusted mean -13.0 +/- 4.6 mg/dl; p-value for global test = 0.005).

CONCLUSION

Our results indicated a strong association of sequence variants of HMGCR, SREBF1 and ABCG8 genes with the reduction of LDL-C after statin treatment in a Chinese population. Future studies on the genes of drug-metabolism enzymes and transporters are warranted.

Evaluation of methods for the determination of cholesterol absorption and synthesis in humans

Cardiovascular disease risk and its associated complications correlate positively with circulating cholesterol levels. Plasma cholesterol levels are maintained by reciprocally related endogenous cholesterol synthesis and cholesterol absorption from dietary and biliary sources. Numerous in vivo clinical methods exist to quantify the absorption and synthesis of cholesterol in humans. This review summarizes these different methods available to study cholesterol absorption and synthesis, highlighting each method's strengths and weaknesses, as well as their applicability in different types of trials.

Pharmacogenomic insights into treatment and management of statin-induced myopathy

Although statins are generally well tolerated, the most common adverse drug reaction from statin therapy is myopathy. This article reviews the current pharmacogenomic knowledge of statin-induced myopathy. Furthermore, we will discuss the importance of recent pharmacogenetic advances for the treatment and management of statin-induced myopathy. Variation in the SLCO1B1 gene is associated with increased incidence of statin-induced myopathy, particularly with simvastatin and less so with other statins. If different pharmacokinetic enzymes and transporters are responsible for susceptibility to myopathy, this may explain differences in the occurrence of statin-induced myopathy in individual patients. Genotyping in patients suffering from statin-induced myopathy may help to personalize the choice of statin for the lowest chance of developing myopathy.