Genetic testing for CYP450 polymorphisms to predict response to clopidogrel: current evidence and test availability. Application: pharmacogenomics

Sex Differences in Clopidogrel Effects Among Young Patients With Acute Coronary Syndrome: A Role for Genetics?

Background

Poorer health outcomes experienced by young women with acute coronary syndrome may be related to sex differences in the safety and efficacy of antiplatelet agents, such as clopidogrel. Polymorphisms in drug metabolism enzyme (cytochrome P450 [CYP] family) genes are independent factors for the variability in response to clopidogrel. However, a sex-specific impact of genetics to explain worse clinical outcomes in women has not been explored extensively. Therefore, our objective was to determine whether an interaction of sex with CYP variants occurs among users of clopidogrel, and if so, its impact on 1-year adverse clinical outcomes.

Methods

We used data from a combined cohort of 2272 patients (median age 49 years; 56% female) hospitalized for acute coronary syndrome. We examined interactions between sex and CYP variants among clopidogrel users at admission and discharge to assess associations with 1-year readmission due to cardiac events.

Results

The case-only analysis of 177 participants on clopidogrel at the time of presentation showed that the risk of an atherothrombotic event was greater in female carriers of the CYP2C9∗3 loss-of-function allele (odds ratio = 3.77, 95% confidence interval = 1.54-9.24). The results of the multivariable logistic regression model for users of clopidogrel at discharge (n = 1733) indicated that women had significantly higher risk of atherothrombotic readmissions at 1 year (odds ratio = 1.55, 95% confidence interval = 1.16-2.07), compared to the risk for men, but the loss-of-function alleles, either individually or through a genetic risk score, were not associated with 1-year readmissions.

Conclusion

This study highlights the need for an improved understanding of the role of sex-by-gene interactions in causing sex differences in drug metabolism.

Risk of major adverse cardiovascular events for concomitant use of clopidogrel and proton pump inhibitors in patients inheriting CYP2C19 loss-of-function alleles: meta-analysis

Background Efficacy of clopidogrel may be diminished due to either co-administration of proton pump inhibitors or carrying CYP2C19 loss-of-function alleles. However, patients may be at greater risk of major adverse cardiovascular events if taking clopidogrel together with proton pump inhibitors and also inherited the CYP2C19 loss-of-function alleles which may cause further reduction of clopidogrel efficacy. This is due to the cumulative effects of drug-drug interactions and drug-gene interactions collectively referred to as multifactorial drug-gene interactions. Aim of the review The aim of this analysis was to estimate aggregated risk of major adverse cardiovascular events for either coronary heart disease or stroke patients with multifactorial drug-gene interactions versus clopidogrel alone with or without drug-gene interactions. Methods Literatures were searched using different resources based on the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. Meta-analysis was performed using RevMan software following either fixed/random effects model based on the levels of heterogeneity. A p value < 0.05 (2-sided) was considered statistically significant. Results In total, five studies consisting 8,802 patients of coronary artery diseases or stroke were included in this meta-analysis in which 3,767 were prescribed clopidogrel alone, 1,931 were concomitantly taking clopidogrel and PPIs, 2,146 were carrying CYP2C19 loss-of-function alleles and 958 were taking both clopidogrel and proton pump inhibitors while also carrying CYP2C19 loss-of-function alleles. It was found that patients with multifactorial drug-gene interactions were associated with significantly increased risk of major adverse cardiovascular events compared to those taking clopidogrel alone without CYP2C19 loss-of-function alleles (12% vs. 5.8%; RR 1.73; 95% CI 1.12-2.67; p = 0.01). Patients with multifactorial drug-gene interactions were also associated with significantly increased risk of major adverse cardiovascular events compared to drug-gene interactions (RR 1.63; 95% CI 1.31-2.03; p < 0.0001). Patients taking clopidogrel with proton pump inhibitors were also associated with 35% significantly increased risk of major adverse cardiovascular events compared to those taking only clopidogrel (RR 1.35; 95% CI 1.11-1.65; p = 0.003). Conclusion Patients inheriting CYP2C19 loss-of-function alleles have significantly increased risk of major adverse cardiovascular events when taking clopidogrel and proton pump inhibitors concurrently.

Clinical pharmacology applications in clinical drug development and clinical care: A focus on Saudi Arabia

Drug development, from preclinical to clinical studies, is a lengthy and complex process. There is an increased interest in the Kingdom of Saudi Arabia (KSA) to promote innovation, research and local content including clinical trials (Phase I-IV). Currently, there are over 650 registered clinical trials in Saudi Arabia, and this number is expected to increase. An important part of drug development and clinical trials is to assure the safe and effective use of drugs. Clinical pharmacology plays a vital role in informed decision making during the drug development stage as it focuses on the effects of drugs in humans. Disciplines such as pharmacokinetics, pharmacodynamics and pharmacogenomics are components of clinical pharmacology. It is a growing discipline with a range of applications in all phases of drug development, including selecting optimal doses for Phase I, II and III studies, evaluating bioequivalence and biosimilar studies and designing clinical studies. Incorporating clinical pharmacology in research as well as in the requirements of regulatory agencies will improve the drug development process and accelerate the pipeline. Clinical pharmacology is also applied in direct patient care with the goal of personalizing treatment. Tools such as therapeutic drug monitoring, pharmacogenomics and model informed precision dosing are used to optimize dosing for patients at an individual level. In KSA, the science of clinical pharmacology is underutilized and we believe it is important to raise awareness and educate the scientific community and healthcare professionals in terms of its applications and potential. In this review paper, we provide an overview on the use and applications of clinical pharmacology in both drug development and clinical care.

Comparison of administration of clopidogrel with aspirin versus aspirin alone in prevention of secondary stroke after transient ischemic attack

BACKGROUND

Patients with transient ischemic attack (TIA) or minor stroke are at risk of strokes. One of the precautionary measures to reduce risk of stroke in these patients is administration of antiplatelet drugs.

METHODS

The aim of this study was comparison of clopidogrel with aspirin versus aspirin alone in prevention of stroke following TIA or acute minor stroke. This clinical trial study was carried out in Farshchian Hospital, Hamadan, Iran in 2018. Fifty-four patients with TIA, isolated visual attacks, and minor stroke were randomly assigned to receive aspirin 80 mg/day or aspirin 80 mg/day and clopidogrel 75 mg/day for 3 months.

RESULTS

After this period, patients were examined for occurrence of myocardial stroke, hemorrhagic/ischemic stroke and drug complications. Ischemic stroke or TIA occurred in 5 (18.5%) patients in clopidogrel-aspirin group and 10 patients (37.1%) in aspirin group (P = 0.12).

CONCLUSION

The study suggests a trend toward superiority of administration of clopidogrel with aspirin versus aspirin alone in protection against secondary stroke. Studies in larger cohorts of patients are needed to verify these results.

Big data hurdles in precision medicine and precision public health

BACKGROUND

Nowadays, trendy research in biomedical sciences juxtaposes the term 'precision' to medicine and public health with companion words like big data, data science, and deep learning. Technological advancements permit the collection and merging of large heterogeneous datasets from different sources, from genome sequences to social media posts or from electronic health records to wearables. Additionally, complex algorithms supported by high-performance computing allow one to transform these large datasets into knowledge. Despite such progress, many barriers still exist against achieving precision medicine and precision public health interventions for the benefit of the individual and the population.

MAIN BODY

The present work focuses on analyzing both the technical and societal hurdles related to the development of prediction models of health risks, diagnoses and outcomes from integrated biomedical databases. Methodological challenges that need to be addressed include improving semantics of study designs: medical record data are inherently biased, and even the most advanced deep learning's denoising autoencoders cannot overcome the bias if not handled a priori by design. Societal challenges to face include evaluation of ethically actionable risk factors at the individual and population level; for instance, usage of gender, race, or ethnicity as risk modifiers, not as biological variables, could be replaced by modifiable environmental proxies such as lifestyle and dietary habits, household income, or access to educational resources.

CONCLUSIONS

Data science for precision medicine and public health warrants an informatics-oriented formalization of the study design and interoperability throughout all levels of the knowledge inference process, from the research semantics, to model development, and ultimately to implementation.

Clinical Pharmacogenomics: Applications in Nephrology

Pharmacogenomics is a tool for practitioners to provide precision pharmacotherapy using genomics. All providers are likely to encounter genomic data in practice with the expectation that they are able to successfully apply it to patient care. Pharmacogenomics tests for genetic variations in genes that are responsible for drug metabolism, transport, and targets of drug action. Variations can increase the risk for drug toxicity or poor efficacy. Pharmacogenomics can, therefore, be used to help select the best medication or aid in dosing. Nephrologists routinely treat cardiovascular disease and manage patients after kidney transplantation, two situations for which there are several high-evidence clinical recommendations for commonly used anticoagulants, antiplatelets, statins, and transplant medications. Successful use of pharmacogenomics in practice requires that providers are familiar with how to access and use pharmacogenomics resources. Similarly, clinical decision making related to whether to use existing data, whether to order testing, and if data should be used in practice is needed to deliver precision medicine. Pharmacogenomics is applicable to virtually every medical specialty, and nephrologists are well positioned to be implementation leaders.

Pharmacogenomics of oral antiplatelet drugs

Pharmacogenomics has been implicated in the response variability of antiplatelet drugs in coronary artery disease (CAD), particularly for aspirin and clopidogrel. A large number of studies and several meta-analyses have been published on this topic, but until recently, there have been no clear conclusions and no definite guidelines on the clinical use of pharmacogenetic testing before prescribing antiplatelet drugs for CAD. In this review, the available evidence is summarized. The most consistent results are on clopidogrel, where CYP2C19 loss-of-function alleles are associated with stent thrombosis events. We recommend to genotype for CYP2C19 loss-of-function alleles in patients with CAD who are to undergo percutaneous coronary intervention and stenting, and to adjust the antiplatelet treatment based on the genotyping results.

Vagal baroreflex activation resulting in acute coronary stent thrombus associated with myocardial infarction: a case report

Background

Percutaneous coronary intervention with stenting in patients with coronary atheromatous stenosis carry an inherent risk of affecting the baroreflex-mediated regulation of hemodynamic alterations, especially for heart rate and blood pressure. To the best of our knowledge, the vagal baroreflex activation associated with acute coronary stent thrombosis in patients who have undergone percutaneous coronary intervention has not been previously reported.

Case presentation

In the present article, we report a case of a Chinese patient (a 75-year-old male) with coronary artery disease who presented with hemodynamic alterations as a complication of vagal baroreflex activation after implantation of overlapping stents, followed by stent thrombosis associated with myocardial infarction.

Conclusion

The patient’s vagal baroreflex sensitivity increased after the coronary stenting procedure. He was successfully treated with intra-aortic balloon pump therapy. Because of its rarity, this case is being reported to emphasize the importance of using intra-aortic balloon pump therapy.

Multi-ethnic distribution of clinically relevant CYP2C genotypes and haplotypes

To determine CYP2C19 and CYP2C8 allele frequencies, 28 coding and/or functional variants were genotyped in 1250 African-American, Asian, Caucasian, Hispanic and Ashkenazi Jewish (AJ) individuals. The combined CYP2C19 variant allele frequencies ranged from ∼0.30 to 0.41; however, the CYP2C8 frequencies were much lower (∼0.04-0.13). After incorporating previously reported CYP2C9 genotyping results from these populations (36 total CYP2C variants), 16 multi-ethnic CYP2C haplotypes were inferred with frequencies >0.5%. Notably, the 2C19*17-2C9*1-2C8*2 haplotype was identified among African-Americans (8%) and Hispanics (2%), indicating that CYP2C19*17 does not always tag a CYP2C haplotype that encodes efficient CYP2C-substrate metabolism. The 2C19*1-2C9*2-2C8*3 haplotype was identified in all populations except African-Americans and additional novel haplotypes were identified in selected populations (for example, 2C19*2-2C9*1-2C8*4 and 2C19*4B-2C9*1-2C8*1), together indicating that both CYP2C19*17 and *2 can be linked with other CYP2C loss-of-function alleles. These results have important implications for pharmacogenomic association studies involving the CYP2C locus and are clinically relevant when administering CYP2C-substrate medications.

Clinical application of high throughput molecular screening techniques for pharmacogenomics

Genetic analysis is one of the fastest-growing areas of clinical diagnostics. Fortunately, as our knowledge of clinically relevant genetic variants rapidly expands, so does our ability to detect these variants in patient samples. Increasing demand for genetic information may necessitate the use of high throughput diagnostic methods as part of clinically validated testing. Here we provide a general overview of our current and near-future abilities to perform large-scale genetic testing in the clinical laboratory. First we review in detail molecular methods used for high throughput mutation detection, including techniques able to monitor thousands of genetic variants for a single patient or to genotype a single genetic variant for thousands of patients simultaneously. These methods are analyzed in the context of pharmacogenomic testing in the clinical laboratories, with a focus on tests that are currently validated as well as those that hold strong promise for widespread clinical application in the near future. We further discuss the unique economic and clinical challenges posed by pharmacogenomic markers. Our ability to detect genetic variants frequently outstrips our ability to accurately interpret them in a clinical context, carrying implications both for test development and introduction into patient management algorithms. These complexities must be taken into account prior to the introduction of any pharmacogenomic biomarker into routine clinical testing.