Pharmacogenetics and personalised medicine

Evaluating the prospective utility of pharmacogenetics reporting among Canadian Armed Forces personnel receiving pharmacotherapy: a preliminary assessment towards precision psychiatric care

Pharmacological interventions for treating posttraumatic stress disorder in Canadian Armed Forces (CAF) members and Veterans often achieve modest results. The field of pharmacogenetics, or the study of how genes influence an individual's response to different medications, offers insight into how prior knowledge of gene-drug interactions may potentially improve the trial-and-error process of drug selection in pharmacotherapy, thereby improving treatment effects and remission rates. Given the relative recency of pharmacogenetics testing and sparse research in military samples, we used pharmacogenetics testing in a small pilot group (n=23) of CAF members and Veterans who were already engaged in pharmacotherapy for a service-related mental health condition to better understand the associated opportunities and challenges of pharmacogenetics testing in this population. Our preliminary evaluation involved: (1) reporting the prevalence of pharmacogenetics testing 'bin' status according to participants' reports ('green', 'yellow' or 'red'; intending to signal 'go', 'caution' or 'stop', regarding the potential for gene-drug interactions); (2) calculating the percentage of currently prescribed psychotropic medications that were assessed and included in the reports; (3) evaluating whether prescribers used pharmacogenetics testing information according to clinical notes and (4) collecting informal feedback from participating psychiatrists. While pharmacogenetics testing appeared to provide valuable information for a number of clients, a major limitation was the number of commonly prescribed medications not included in the reports.

Establishing the Value of Diagnostic and Prognostic Tests in Health Technology Assessment

In recent years, Health Technology Assessment (HTA) processes specific to diagnostics and prognostic tests have been created in response to the increased pressure on health systems to decide not only which tests should be used in practice but also the best way to proceed, clinically, from the information they provide. These technologies differ in the way value is accrued to the population of users, depending critically on the value of downstream health care choices. This paper defines an analytical framework for establishing the value of diagnostic and prognostic tests for HTA in a way that is consistent with methods used for the evaluation of other health care technologies. It assumes a linked-evidence approach where modeling is required, and incorporates considerations regarding several different areas of policy, such as personalized medicine. We initially focus on diagnostic technologies with dichotomous results, and then extend the framework by considering diagnostic tests that provide more complex information, such as continuous measures (for example, blood glucose measurements) or multiple categories (such as tumor classification systems). We also consider how the methods of assessment differ for prognostic information or for diagnostics without a reference standard. Throughout, we propose innovative graphical ways of summarizing the results of such complex assessments of value.

Precision medicine: does ethnicity information complement genotype-based prescribing decisions?

Inter-ethnic differences in drug response are all too well known. These are underpinned by a number of factors, including pharmacogenetic differences across various ethnic populations. Precision medicine relies on genotype-based prescribing decisions with the aim of maximizing efficacy and mitigating the risks. When there is no access to genotyping tests, ethnicity is frequently regarded as a proxy of the patient's probable genotype on the basis of overall population-based frequency of genetic variations in the ethnic group the patient belongs to, with some variations being ethnicity-specific. However, ever-increasing transcontinental migration of populations and the resulting admixing of populations have undermined the utility of self-identified ethnicity in predicting the genetic ancestry, and therefore the genotype, of the patient. An example of the relevance of genetic ancestry of a patient is the inadequate performance of European-derived pharmacogenetic dosing algorithms of warfarin in African Americans, Brazilians and Caribbean Hispanics. Consequently, genotyping a patient potentially requires testing for all known clinically actionable variants that the patient may harbour, and new variants that are likely to be identified using state-of the art next-generation sequencing-based methods. Furthermore, self-identified ethnicity is associated with a number of ethnicity-related attributes and non-genetic factors that potentially influence the risk of phenoconversion (genotype-phenotype discordance), which may adversely impact the success of genotype-based prescribing decisions. Therefore, while genotype-based prescribing decisions are important in implementing precision medicine, ethnicity should not be disregarded.

The promise of metabolic phenotyping in gastroenterology and hepatology

Disease risk and treatment response are determined, at the individual level, by a complex history of genetic and environmental interactions, including those with our endogenous microbiomes. Personalized health care requires a deep understanding of patient biology that can now be measured using a range of '-omics' technologies. Patient stratification involves the identification of genetic and/or phenotypic disease subclasses that require different therapeutic strategies. Stratified medicine approaches to disease diagnosis, prognosis and therapeutic response monitoring herald a new dimension in patient care. Here, we explore the potential value of metabolic profiling as applied to unmet clinical needs in gastroenterology and hepatology. We describe potential applications in a number of diseases, with emphasis on large-scale population studies as well as metabolic profiling on the individual level, using spectrometric and imaging technologies that will leverage the discovery of mechanistic information and deliver novel health care solutions to improve clinical pathway management.

Personalized medicine: the impact on chemistry

An effective strategy for personalized medicine requires a major conceptual change in the development and application of therapeutics. In this article, we argue that further advances in this field should be made with reference to another conceptual shift, that of network pharmacology. We examine the intersection of personalized medicine and network pharmacology to identify strategies for the development of personalized therapies that are fully informed by network pharmacology concepts. This provides a framework for discussion of the impact personalized medicine will have on chemistry in terms of drug discovery, formulation and delivery, the adaptations and changes in ideology required and the contribution chemistry is already making. New ways of conceptualizing chemistry's relationship with medicine will lead to new approaches to drug discovery and hold promise of delivering safer and more effective therapies.

Novel multistranded, alternative, plasmid and helical transitional DNA and RNA microarrays: implications for therapeutics

Novel multistranded and alternative DNA, RNA and plasmid microarrays (transitional structural nucleic acid microarrays) have been developed that allows for the immobilization of intact, nondenatured, double-stranded DNA, double-stranded RNA, and alternative and multistranded nucleic acids. It also allows for the study of transitional changes that occur in the structure of DNA and RNA. Alternative types of DNA, RNA and multistranded nucleic acids are immobilized by a variety of different surface chemistries (i.e., noncovalent or covalent) onto a novel substrate surface. This technology represents the next generation of microarrays, which will aid in the characterization of nucleic acid structure and function, and accelerate the discovery of drugs that bind to nucleic acids. In addition, we demonstrate four novel techniques that are the first practical applications of the microarray, that is, transitional structural chemogenomics, transitional structural chemoproteomics, transitional structural pharmacogenomics and transitional structural pharmacoproteomics. These novel nucleic acid microarrays, together with pharmacogenomics, can be used to improve the study of DNA and RNA structure, gene expression, drug development and treatment of various diseases.

Public Health Genomics (PHG): From Scientific Considerations to Ethical Integration

Recent advances in our understanding of the human genome have raised high hopes for the creation of personalized medicine able to predict diseases well before they occur, or that will lead to individualized and therefore more effective treatments. This possibility of a more accurate science of the prevention and surveillance of disease also illuminates the field of public health, where the translation of genomic knowledge could provide tools enhancing the capacity of public health authorities to promote health and prevent diseases. But beyond scientific considerations, the use of genomics in public health research and interventions gives rise to several ethical and social issues of great importance. Considering the impact that PHG could have on the future of public health while still paying attention to the uncertainty surrounding the use of genomic databases for the benefit of populations, this article seeks to explore the promise of genomics in public health and the ethical issues that emerge from its application.

Real-Time PCR: Revolutionizing Detection and Expression Analysis of Genes

Invention of polymerase chain reaction (PCR) technology by Kary Mullis in 1984 gave birth to real-time PCR. Real-time PCR - detection and expression analysis of gene(s) in real-time - has revolutionized the 21(st) century biological science due to its tremendous application in quantitative genotyping, genetic variation of inter and intra organisms, early diagnosis of disease, forensic, to name a few. We comprehensively review various aspects of real-time PCR, including technological refinement and application in all scientific fields ranging from medical to environmental issues, and to plant.

Cellular pharmacodynamics of immunosuppressive drugs for individualized medicine

The therapeutic effects of immunosuppressive drugs are known to deviate largely between patients, but efficient strategies for the differentiation of patients who show clinical resistance to immunosuppressive therapies have not been established. Accordingly, a considerable number of patients receive treatment with immunosuppressive drugs despite the onset of serious side effects and poor responses. Cellular pharmacodynamics of immunosuppressive drugs in vitro using peripheral lymphocytes derived from each patient, an attractive way to distinguish resistant patients, is respected and has been applied to the carrying out of individualized immunosuppressive therapy. In this article, I summarize experimental procedures for assaying immune cell responses to immunosuppressive drugs in vitro, and highlight the relationship between cellular sensitivity to immunosuppressive drugs and the therapeutic efficacy of drugs in organ transplantation and several immunological disorders. I will also overview the molecular mechanisms and genetic bases for cellular and clinical resistance to immunosuppressive drugs. Lastly, the future clinical prospects for the application of in vitro drug sensitivity tests for "patient-tailored" immunosuppressive therapies are discussed.

Pharmacogenetics and pharmacogenomics: origin, status, and the hope for personalized medicine

Pharmacogenetics arose with studies of single genes, which had major effects on the action of particular drugs. It turned into pharmacogenomics through realization that the controls of most drug responses are multifactorial. Then, variable gene expression posed new problems, for example what do drugs do to genes, or how useful is any genetic pretesting of a person? A common disease may be caused by different groups of genes in different people, who therefore require different drugs for treatment. Personalized medicine is currently represented by a physician's attention to a patients age, sex, or ethnic background, that is groups showing smaller genetic variation than is typical for general humanity. Occasionally, there is also the use of single-gene pretesting of a patient before drug administration. Over time, improvements in multigenic testing promise to increase the role of personalized medicine. However, the many pharmacogenomic complexities, and particularly time-dependent changes of gene expression, will never allow personalized medicine to become an error-free entity.

Racializing drug design: implications of pharmacogenomics for health disparities

Current practices of using "race" in pharmacogenomics research demands consideration of the ethical and social implications for understandings of group difference and for efforts to eliminate health disparities. This discussion focuses on an "infrastructure of racialization" created by current trajectories of research on genetic differences among racially identified groups, the use of race as a proxy for risk in clinical practice, and increasing interest in new market niches by the pharmaceutical industry. The confluence of these factors has resulted in the conflation of genes, disease, and race. I argue that public investment in pharmacogenomics requires careful consideration of current inequities in health status and social and ethical concerns over reifying race and issues of distributive justice.

Genetic epidemiology and public health: hope, hype, and future prospects

Genetic epidemiology is a rapidly expanding research field, but the implications of findings from such studies for individual or population health are unclear. The use of molecular genetic screening currently has some legitimacy in certain monogenic conditions, but no established value with respect to common complex diseases. Personalised medical care based on molecular genetic testing is also as yet undeveloped for common diseases. Genetic epidemiology can contribute to establishing the causal nature of environmentally modifiable risk factors, through the application of mendelian randomisation approaches and thus contribute to appropriate preventive strategies. Technological and other advances will allow the potential of genetic epidemiology to be revealed over the next few years, and the establishment of large population-based resources for such studies (biobanks) should contribute to this endeavour.

Pharmacogenetics and geographical ancestry: implications for drug development and global health

Understanding and harnessing genomic variation will contribute significantly to improving the health of people in developing countries. We need to explore the nexus between pharmacogenetics, genotyping projects in developing countries, and the evolution of the pharmaceutical industry in both the developed and developing worlds. Here, we argue that, for the foreseeable future, we should focus not on boutique 'personalized' medicine, but on carefully defined differences between populations and ethical ways of using emerging genomics knowledge to develop drugs and improve health.

High-throughput screening assays for the assessment of CYP2C9*1, CYP2C9*2, and CYP2C9*3 metabolism using fluorogenic Vivid substrates

CYP2C9 is a genetically polymorphic human cytochrome P450 isozyme involved in the oxidative metabolism of many drugs, including nonsteroidal anti-inflammatory compounds. Individuals genotyped heterozygous or homozygous for CYP2C9 allelic variants have demonstrated altered metabolism of some drugs primarily metabolized by CYP2C9. The ability to expand screening of CYP2C9 allelic variants to a larger set of drugs and pharmaceutical agents would contribute to a better understanding of the significance of CYP2C9 polymorphisms in the population and to predictions of possible outcomes. The authors report the development of an in vitro fluorescence-based assay employing recombinant CYP2C9 variants (CYP2C9*1, CYP2C9*2, and CYP2C9*3) and fluorogenic Vivid(R) CYP2C9 substrates to explore the effects of CYP2C9 polymorphisms on drug metabolism, using drugs primarily metabolized by CYP2C9. Several chemically diverse fluorogenic substrates (Vivid(R) CYP2C9 blue, green, and red substrates) were used as prototypic probes to obtain in vitro CYP2C9 metabolic rates and kinetic parameters, such as apparent K(m), V(max), and V(max)/K(m) ratios for each allelic variant. In addition, a diverse panel of drugs was screened as assay modifiers with CYP2C9*1, CYP2C9*2, CYP2C9*3, and the fluorogenic Vivid(R) CYP2C9 substrates. The inhibitory potential of this large group of chemically diverse drugs and compounds has been assessed on the basis of their ability to compete with Vivid(R) CYP2C9 substrates in fluorescent reporter assays, thus providing a sensitive and quick assessment of polymorphism-dependent changes in CYP2C9 metabolism.

personalized medicine and pharmacogenomics: ethical and social challenges

Recent developments in human genetic variation research have fueled predictions of an imminent era of personalized medicine. Defined as a shift toward greater integrated and heuristic innovation in healthcare, personalized medicine seeks to create differentiated strategies for the prevention of disease defined at the molecular level [1] . Recent developments in gene sequencing technologies have focused efforts toward improving efficacy and efficiency in the drug development process. Emerging from the discipline of pharmacogenetics, pharmacogenomics - the study of gene-to-gene interactions through the use of high-throughput technologies - has gained attention as the field most able to deliver on the promises of genomic medicine [2] . The distinction between pharmacogenetics and pharmacogenomics is not clear; while some have argued that differences of scale and focus distinguish the fields, this article uses the term, 'pharmacogenomics', to mean the broad scope of research on inherited variation in drug response. Through differential diagnosis, drug response is being linked to molecular subgroups that may allow for the development of 'tailored' medications [3] . However, several challenges confront these potential benefits. Critical to the success of pharmacogenomics and personalized drug therapies are the creation of large databases containing human genotypic and phenotypic information, the adoption of pharmacogenomic testing as a standard of medical care, and greater regulatory guidance on balancing commercial and public health priorities. In anticipation of these healthcare trajectories, serious engagement with the ethical and social implications of pharmacogenomics is needed. This article reviews several of these issues and highlights concerns that must be addressed in anticipation of personalized drug development.

Genetic variation and exposure related risk estimation: will toxicology enter a new era? DNA repair and cancer as a paradigm

With the vast technological and informational resources increasingly available from investments in "genomics," toxicology and much of biological science, is faced with previously undreamed of opportunities and equally daunting challenges. The ability to generate the large quantities of data becoming routinely available could not be imagined a decade ago. The complexities of data analysis are increasingly the rate-limiting element in scientific advances. The expectations that these large scientific investments will reduce the incidence of human disease and improve health are very high. An emphasis on genetic variation and Toxicogenetics is expected to yield risk estimates for specific rather than average individuals and individuals with varied lifestyles and complex patterns of exposure. Examples from studies of polymorphic variation in DNA repair genes in the healthy population and cancer risk highlight the complexity and challenges of incorporating genetic variation into quantitative estimates of risk associated with environmentally relevant exposures. Similar issues exist in selecting the animal models most appropriate for predicting human risk from environmental exposures to toxic agents.

Metabolomics in the opening decade of the 21st century: building the roads to individualized health

It is rapidly becoming possible to measure hundreds or thousands of metabolites in small samples of biological fluids or tissues. This makes it possible to assess the metabolic component of nutritional phenotypes and will allow individualized dietary recommendations. ASNS has to take action to ensure that appropriate technologies are developed and that metabolic databases are constructed with the right inputs and organization. The relations between diet and metabolomic profiles and between those profiles and health and disease must be established. ASNS also should consider the social implications of these advances and plan for their appropriate utilization.

What is the impact of the ACE gene insertion/deletion (I/D) polymorphism on the clinical effectiveness and adverse events of ACE inhibitors?--Protocol of a systematic review

Background

The Angiotensin Converting Enzyme (ACE) insertion/deletion (I/D) polymorphism has received much attention in pharmacogenetic research because observed variations in response to ACE inhibitors might be associated with this polymorphism. Pharmacogenetic testing raises the hope to individualise ACE inhibitor therapy in order to optimise its effectiveness and to reduce adverse effects for genetically different subgroups. However, the extent of its effect modification in patients treated with ACE inhibitors remains inconclusive. Therefore our objective is to quantify the effect modification of the insertion/deletion polymorphism of the angiotensin converting enzyme gene on any surrogate and clinically relevant parameters in patients with cardiovascular diseases, diabetes, renal transplantation and/or renal failure.

Methods

Systematic Review. We will perform literature searches in six electronic databases to identify randomised controlled trials comparing the effectiveness and occurrence of adverse events of ACE inhibitor therapy against placebo or any active treatment stratified by the I/D gene polymorphism. In addition, authors of trials, experts in pharmacogenetics and pharmaceutical companies will be contacted for further published or unpublished data. Hand searching will be accomplished by reviewing the reference lists of all included studies. The methodological quality of included papers will be assessed. Data analyses will be performed in clinically and methodologically cogent subgroups. The results of the quantitative assessment will be pooled statistically where appropriate to produce an estimate of the differences in the effect of ACE inhibitors observed between the three ACE genotypes.

Discussion

This protocol describes a strategy to quantify the effect modification of the ACE polymorphism on ACE inhibitors in relevant clinical domains using meta-epidemiological research methods. The results may provide evidence for the usefulness of pharmacogenetic testing for individualised ACE inhibitor therapy.

The role of "genetics" in popular understandings of race in the United States

The increase in public representation of the science-based concept "genetics" in the mass media might be expected to have a major impact on public understanding of the concept of "race." A model of lay understandings of the role of genetics in the contemporary United States is offered based on focus group research, random digit dial surveys, and community based surveys. That model indicates that lay people identify are primarily by physical features, but these identifications are categorized into a variety of groupings that may be regional, national, or linguistic. Although they believe that physical appearance is caused largely by genetics, and therefore that race has a genetic basis, they do not uniformly conclude, however, that all perceived racial characteristics are genetically based. Instead, they vary in the extent to which they attribute differences to cultural, personal, and genetic factors.

Clinical Pharmacology

The dose of a drug is a major determinant of its safety, and establishing a safe dose of a novel drug is a prime objective during clinical development. The design of pre-marketing clinical trials precludes the representation of important subpopulations such as children, the elderly and people with co-morbidities. Therefore, postmarketing surveillance (PMS) activities are required to monitor the safety profile of drugs in real clinical practice. Furthermore, individual variations in pharmacogenetic profiles, the immune system, drug metabolic pathways and drug-drug interactions are also important factors in the occurrence of adverse drug reactions. Thus, the safety of a drug is a major clinical consideration before and after it is marketed. A multidisciplinary approach is required to enhance the safety profile of drugs at all stages of development, including PMS activities. Clinical pharmacology encompasses a range of disciplines and forms the backbone of drug safety consideration during clinical drug development. In this review we give an overview of the clinical drug development process and consider its limitations. We present a discussion of several aspects of clinical pharmacology and their application to enhancing drug safety. Pharmacokinetic-pharmacodynamic modelling provides a method of predicting a clinically safe dose; consideration of drug pharmacokinetics in special populations may enhance safe therapeutics in a wider spectrum of patients, while pharmacogenetics provides the possibility of genotype-specific therapeutics. Pharmacovigilance activities are also discussed. Given the complex nature and unpredictability of type B reactions, PMS activities are crucial in managing the risks drugs pose to the general population. The various aspects of clinical pharmacology discussed make a strong case for this field as the backbone of optimising and promoting safe development and use of drugs.