Pharmacogenomic insights into treatment and management of statin-induced myopathy

A pilot study on the association between SLCO1B1 RS4363657 polymorphism and muscle adverse events in adults with newly diagnosed dyslipidaemia who were prescribed a statin: the Malaysian primary health care cohort

Introduction: Statin, the first-line treatment for dyslipidaemia, may have suboptimal adherence due to its associated muscle adverse events. These data, however, remain limited. Aim: To determine the association of serum creatine kinase (CK) and SLCO1B1 rs4363657 polymorphism with statin-associated muscle adverse events (SAMAE) among dyslipidaemia participants. Methods: This was a prospective cohort study at government health clinics involving newly diagnosed adults with dyslipidaemia. SAMAE were recorded based on the patient's complaint after a month on statin. CK was taken at baseline and follow-up. Genetic profiling was performed for SLCO1B1 rs4363657 polymorphism. Results: Among 118 participants, majority were Malay (72%) males (61%) with a mean age of 49 ± 12.2 years old and prescribed lovastatin (61.9). There was a significant association between statin types (lovastatin and simvastatin) and SAMAE (p = 0.0327); no significant association noted between CK and SAMAE (p = 0.5637). The SLCO1B1 rs4363657 polymorphism was significantly associated SAMAE (p < 0.0001). Conclusions: In this first pilot study of a multiethnic Malaysian population, the incidence of SAMAE was 18.6%. SAMAE were significantly higher in subjects on lovastatin compared to simvastatin. SLCO1B1 rs4363657 polymorphism was a significant risk factor for SAMAE.

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.

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.

The SLCO1B1 c.521T>C polymorphism is associated with dose decrease or switching during statin therapy in the Rotterdam Study

OBJECTIVE

The SLCO1B1 c.521T>C polymorphism is associated with statin plasma levels and simvastatin-induced adverse drug reactions. We studied whether the c.521T>C polymorphism is associated with dose decreases or switches to other cholesterol-lowering drugs during simvastatin and atorvastatin therapy, because these events are indicators of adverse drug reactions.

MATERIALS AND METHODS

We identified 1939 incident simvastatin and atorvastatin users in the Rotterdam Study, a population-based cohort study. Associations were studied using Cox proportional hazards analysis. Meta-analysis was performed with data from the Utrecht Cardiovascular Pharmacogenetics study.

RESULTS

Simvastatin users with the c.521 CC genotype had a significantly higher risk of a dose decrease or switch than users with the TT genotype [hazard ratio (HR) 1.74, 95% confidence interval (CI) 1.05-2.88]. Female sex, age below 70 years, and low starting dose were risk factors. In atorvastatin users with starting dose of more than 20 mg, the risk of a dose decrease or switch was higher in users carrying a C allele than in users with the TT genotype (HR 3.26, 95% CI 1.47-7.25). In the meta-analysis the association in simvastatin users remained, with a significantly higher risk of a dose decrease or switch in simvastatin users with two minor alleles (HR 1.69, 95% CI 1.05-2.73). For atorvastatin users no significant association was found.

CONCLUSION

In simvastatin users in the Rotterdam Study, we demonstrated an association between the c.521T>C polymorphism and dose decrease or switching, as indicators of adverse drug reactions, and provided risk factors for this association. For atorvastatin, an association was found in users with a starting dose of more than 20 mg.

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

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

Statins personalized

3-Hydroxy-3-methylglutaryl coenzyme A reductase inhibitor medications, commonly referred to as statins, are among the most widely prescribed medications. Variation in individual response to statins concerning low-density lipoprotein cholesterol reduction, clinical event benefit, and side effects has been observed. Some of this variability is attributed to demographic and environmental issues, chief of which is compliance. A large portion of the individual response to statin therapy is attributed to single nucleotide polymorphisms that have recently been elucidated, several of which seem to have clinical utility.

Pharmacogenetics and human genetic polymorphisms

The term pharmacogenetics was first used in the late 1950s and can be defined as the study of genetic factors affecting drug response. Prior to formal use of this term, there was already clinical data available in relation to variable patient responses to the drugs isoniazid, primaquine and succinylcholine. The subject area developed rapidly, particularly with regard to genetic factors affecting drug disposition. There is now comprehensive understanding of the molecular basis for variable drug metabolism by the cytochromes P450 and also for variable glucuronidation, acetylation and methylation of certain drugs. Some of this knowledge has already been translated to the clinic. The molecular basis of variation in drug targets, such as receptors and enzymes, is generally less well understood, although there is consistent evidence that polymorphisms in the genes encoding the β-adrenergic receptors and the enzyme vitamin K epoxide reductase is of clinical importance. The genetic basis of rare idiosyncratic adverse drug reactions had also been examined. Susceptibility to reactions affecting skin and liver appears to be determined in part by the HLA (human leucocyte antigen) genotype, whereas reactions affecting the heart and muscle may be determined by polymorphisms in genes encoding ion channels and transporters respectively. Genome-wide association studies are increasingly being used to study drug response and susceptibility to adverse drug reactions, resulting in identification of some novel pharmacogenetic associations.