Recommendations from the EGAPP Working Group: testing for cytochrome P450 polymorphisms in adults with nonpsychotic depression treated with selective serotonin reuptake inhibitors

Novel drug metabolism indices for pharmacogenetic functional status based on combinatory genotyping of CYP2C9, CYP2C19 and CYP2D6 genes

AIMS

We aim to demonstrate clinical relevance and utility of four novel drug-metabolism indices derived from a combinatory (multigene) approach to CYP2C9, CYP2C19 and CYP2D6 allele scoring. Each index considers all three genes as complementary components of a liver enzyme drug metabolism system and uniquely benchmarks innate hepatic drug metabolism reserve or alteration through CYP450 combinatory genotype scores.

METHODS

A total of 1199 psychiatric referrals were genotyped for polymorphisms in the CYP2C9, CYP2C19 and CYP2D6 gene loci and were scored on each of the four indices. The data were used to create distributions and rankings of innate drug metabolism capacity to which individuals can be compared. Drug-specific indices are a combination of the drug metabolism indices with substrate-specific coefficients.

RESULTS

The combinatory drug metabolism indices proved useful in positioning individuals relative to a population with regard to innate drug metabolism capacity prior to pharmacotherapy. Drug-specific indices generate pharmacogenetic guidance of immediate clinical relevance, and can be further modified to incorporate covariates in particular clinical cases.

CONCLUSIONS

We believe that this combinatory approach represents an improvement over the current gene-by-gene reporting by providing greater scope while still allowing for the resolution of a single-gene index when needed. This method will result in novel clinical and research applications, facilitating the translation from pharmacogenomics to personalized medicine, particularly in psychiatry where many drugs are metabolized or activated by multiple CYP450 isoenzymes.

Pharmacogenomics and personalized medicine in neuropsychiatry

Despite the need for more effective treatments for psychiatric disorders, development of new medications has stalled. Here we discuss the promise of personalized medicine in developing more efficacious and individualized pharmacotherapies that take into account genetic variation and target groups of patients who share biology, not just symptoms.

Personalizing medicine with clinical pharmacogenetics

Clinical genetic testing has grown substantially over the past 30 years as the causative mutations for Mendelian diseases have been identified, particularly aided in part by the recent advances in molecular-based technologies. Importantly, the adoption of new tests and testing strategies (e.g., diagnostic confirmation, prenatal testing, and population-based carrier screening) has often been met with caution and careful consideration before clinical implementation, which facilitates the appropriate use of new genetic tests. Although the field of pharmacogenetics was established in the 1950s, clinical testing for constitutional pharmacogenetic variants implicated in interindividual drug response variability has only recently become available to help clinicians guide pharmacotherapy, in part due to US Food and Drug Administration-mediated product insert revisions that include pharmacogenetic information for selected drugs. However, despite pharmacogenetic associations with adverse outcomes, physician uptake of clinical pharmacogenetic testing has been slow. Compared with testing for Mendelian diseases, pharmacogenetic testing for certain indications can have a lower positive predictive value, which is one reason for underutilization. A number of other barriers remain with implementing clinical pharmacogenetics, including clinical utility, professional education, and regulatory and reimbursement issues, among others. This review presents some of the current opportunities and challenges with implementing clinical pharmacogenetic testing.

Pharmacogenomics of antidepressants for major depressive disorder

Major depressive disorder (MDD) is a common disorder, affecting approximately 10% of adults in the United States each year. The primary treatment options for moderate to severe MDD are antidepressant medications, mainly selective serotonin reuptake inhibitors (SSRIs). Current guidelines recommend an initial trial of 4–8 weeks to determine if a medication is effective for a patient. Through the use of pharmacogenomics, it may be possible to predict whether patients will respond to and tolerate SSRIs. This article discusses several genes and alleles that may play a role in a patient's response to SSRIs.

Pharmacogenetics in randomized controlled trials: considerations for trial design

Pharmacogenetic analyses of clinical trials aim to either detect whether a subgroup of patients identified by genetic characteristics responds differently to the treatment or to verify whether a proposed genotype-guided treatment is beneficial over standard care. This article describes three different trial designs, differing in the timing of randomization and genotyping. Each design has its own advantages, and the objectives and conditions under which each one is most suited are discussed.

Genetic polymorphisms of cytochrome P450 enzymes and antidepressant metabolism

INTRODUCTION

The cytochrome P450 (CYP) enzymes are the major enzymes responsible for Phase I reactions in the metabolism of several substances, including antidepressant medications. Thus, it has been hypothesized that variants in the CYP network may influence antidepressant efficacy and safety. Nonetheless, data on this field are still contradictory. The authors aim to give an overview of the published studies analyzing the influence of CYP highly polymorphic loci on antidepressant treatment in order to translate the acquired knowledge to a clinical level.

AREAS COVERED

The authors collected and compared experimental works and reviews published from the 1980s to the present and included in the Medline database. The included studies pertain to the effects of CYP gene polymorphisms on antidepressant pharmacokinetic parameters and clinical outcomes (response and drug-related adverse effects), with a focus on applications in clinical practice. The authors focused mainly on in vivo studies in humans (patients or healthy volunteers).

EXPERT OPINION

Great variability in antidepressant metabolism among individuals has been demonstrated. Thus, with the current interest in individualized medicine, several genetic tests to detect CYP variants have been produced. They provide a potentially useful way to anticipate some clinical outcomes of antidepressant treatment, although they will only be extensively used in clinical practice if precise and specific treatment options and guidelines based on genetic tests can be provided.

Pharmacogenomics of antidepressant treatment effects

There has been considerable promise and hope that pharmacogenomics will optimize existing treatments for major depression, as well as identify novel targets for drug discovery. Immediately after the sequencing of the human genome, there was much hope that tremendous progress in pharmacogenomics would rapidly be achieved. In the past 10 years this initial enthusiasm has been replaced by a more sober optimism, as we have gone a long way towards the goal of guiding therapeutics based on genomics. While the effort to translate discovery to clinical applications is ongoing, we now have a vast body of knowledge as well as a clear direction forward. This article will provide a critical appraisal of the state of the art in the pharmacogenomics of depression, both in terms of pharmacodynamics and pharmacokinetics.

Evidence-based classification of recommendations on use of genomic tests in clinical practice: dealing with insufficient evidence

Numerous genomic tests continue to emerge as potential tools in the diagnosis, treatment, prognosis, and prevention for a wide variety of common human diseases. To date, most of these tests have "insufficient evidence" of clinical validity and utility for their use in clinical practice. Explicit and quantitative tools can be used in the evaluation of direct and indirect evidence on the utility of genomic tests. As suggested in an article in this month's issue by Veenstra et al., a recommendation matrix can be developed based on the amount of certainty of the evidence and the assessment of the risk-benefit profile. To supplement the current binary (up or down) evidence-based recommendation for use, it is worthwhile to explore all available data to develop a three-tier evidence-based recommendation classification of genomic tests ("use in practice," "promote informed decision-making," and "discourage use"). Promoting informed decision making may be a valuable recommendation for tests for which there is sufficient information on analytic and clinical validity and for which the risk/benefit analysis on clinical utility is promising but not definitive. This approach could provide interim guidance for clinical practice, while rigorous outcomes research is conducted to assess the impact of such tests on patients, families, and population health outcomes.

Do guidelines recommending pharmacogenetic testing of psychiatric patients affect treatment costs and the use of healthcare services?

Aim: To identify the effects of local recommendations of pharmacogenetic testing in psychiatry with respect to treatment costs. Methods: Based on Danish patient registers, individual treatment costs within a 365-day period at three psychiatric hospitals recommending and using pharmacogenetic testing is compared retrospectively with treatment costs at other Danish psychiatric hospitals using alternate treatment strategies. Primary outcome of interest is total direct costs analyzed by multilevel modelling. Secondary outcome measures are healthcare consumption within specific sectors analyzed by Tobitregressions. Results: Costs among patients treated at hospitals recommending and using pharmacogenetic testing were not found to be statistically significantly different from costs among patients treated at sites using alternate treatment strategies. In spite of recommendations to test all patients the uptake of the test was, however, low (26—31 %). Treatment practice using routine therapeutic drug monitoring (in Ãrhus) shows a trend towards lower costs. Conclusions: Based on this natural experiment we were not able to document statistically significant differences in total costs between treatment sites that had guidelines recommending pharmacogenetic testing, relative to sites without such guidelines, over a period of one year. However, guidelines of pharmacogenetic testing and possibly also therapeutic drug monitoring seem to lead to reductions in costs for primary care services. In the case of the former, reductions do, however, seem to be outweighed by increases in costs for psychiatric and non-psychiatric inpatient stays. In conclusion, no statistically significant differences in total direct costs across sites with different treatment strategies were found.

The promise and reality of pharmacogenetics in psychiatry

Existing psychotropic medications for the treatment of mental illnesses, including antidepressants, mood stabilizers, and antipsychotics, are clinically suboptimal. They are effective in only a subset of patients or produce partial responses, and they are often associated with debilitating side effects that discourage adherence. There is growing enthusiasm in the promise of pharmacogenetics to personalize the use of these treatments to maximize their efficacy and tolerability; however, there is still a long way to go before this promise becomes a reality. This article reviews the progress that has been made in research toward understanding how genetic factors influence psychotropic drug responses and the challenges that lie ahead in translating the research findings into clinical practices that yield tangible benefits for patients with mental illnesses.

Health system implications of direct-to-consumer personal genome testing

Direct-to-consumer personal genome testing is now widely available to consumers. Proponents argue that knowledge is power but critics worry about consumer safety and potential harms resulting from misinterpretation of test information. In this article, we consider the health system implications of direct-to-consumer personal genome testing, focusing on issues of accountability, both corporate and professional.

A formal risk-benefit framework for genomic tests: facilitating the appropriate translation of genomics into clinical practice

PURPOSE

Evaluation of genomic tests is often challenging because of the lack of direct evidence of clinical benefit compared with usual care and unclear evidence requirements. To address these issues, this study presents a risk-benefit framework for assessing the health-related utility of genomic tests.

METHODS

We incorporated approaches from a variety of established fields including decision science, outcomes research, and health technology assessment to develop the framework. Additionally, we considered genomic test stakeholder perspectives and case studies.

RESULTS

We developed a three-tiered framework: first, we use decision-analytic modeling techniques to synthesize data, project incidence of clinical events, and assess uncertainty. Second, we defined the health-related utility of genomic tests as improvement in health outcomes as measured by clinical event rates, life expectancy, and quality-adjusted life-years. Finally, we displayed results using a risk-benefit policy matrix to facilitate the interpretation and implementation of findings from these analyses.

CONCLUSION

A formal risk-benefit framework may accelerate the utilization and practice-based evidence development of genomic tests that pose low risk and offer plausible clinical benefit, while discouraging premature use of tests that provide little benefit or pose significant health risks compared with usual care.

Systematic review of psychosocial benefits and harms of genetic testing

Genetic testing can help individuals and families by giving them a sense of control over their futures; however, results of some types of testing cause individuals and their families great distress and anxiety. The purpose of this paper is to report findings from a systematic review of literature about perceived benefits and harms associated with genetic testing. A second purpose was to determine if perceived benefits and harms varied by age and gender. We reviewed a sample of 30 articles published between 1997 and 2009. Most of the articles were other literature reviews. We summarized the benefits and harms associated with each type of genetic testing and made recommendations for future study. As technologies increase, genetic testing will expand and psychiatric mental health nurses must be prepared to meet the challenges of psychosocial disorders that may develop in response to genetic testing.

Outcomes of interest in evidence-based evaluations of genetic tests

Genetic tests are increasingly available for use in traditional clinical practice settings and through direct-to-consumer marketing. The need for evidence-based information and guidance on their appropriate use has never been more apparent. The independent Working Group of the Evaluation of Genomic Applications in Practice and Prevention Initiative commissions evidence-based reviews and develops recommendations to inform decision making surrounding the implementation of genetic tests and other applications of genomic technologies into clinical practice. A critical component of this analysis involves the identification and appropriate weighting of relevant health outcomes from genetic testing. Impacts of testing on morbidity and mortality are central considerations although research to document such outcomes can be challenging to conduct. In considering the broader impacts of genetic tests on the individual, familial and societal levels, psychosocial outcomes often take on increasing importance, and their systematic evaluation is a challenge for traditional methods of evidence-based review. Incorporating these types of outcomes in evidence-based processes is possible, however, and necessary to extract balanced and complete (or as complete as available data will allow) information on potential benefits and on potential harms. The framework used by the Evaluation of Genomic Applications in Practice and Prevention Working Group in considering, categorizing, and weighting health-related outcomes as applied to genomic technologies is presented here.

Genetic predisposition to adverse drug reactions in the intensive care unit

Adverse drug reactions are a significant public health problem that leads to mortality, hospital admissions, an increased length of stay, increasing healthcare costs, and withdrawal of drugs from market. Intensive care unit patients are particularly vulnerable and are at an elevated risk. Critical care practitioners, regulatory agencies, and the pharmaceutical industry aggressively seek biomarkers to mitigate patient risk. The rapidly expanding field of pharmacogenomics focuses on the genetic contributions to the variability in drug response. Polymorphisms may explain why some groups of patients have the expected response to pharmacotherapy whereas others experience adverse drug reactions. Historically, genetic association studies have focused on characterizing the effects of variation in drug metabolizing enzymes on pharmacokinetics. Recent work has investigated drug transporters and the variants of genes encoding drug targets, both intended and unintended, that comprise pharmacodynamics. This has led to an appreciation of the role that genetics plays in adverse drug reactions that are either predictable extensions of a drug's known therapeutic effect or idiosyncratic.This review presents the evidence for a genetic predisposition to adverse drug reactions, focusing on gene variants producing alterations in drug pharmacokinetics and pharmacodynamics in intensive care unit patients. Genetic biomarkers with the strongest associations to adverse drug reaction risk in the intensive care unit are presented along with the medications involved. Variant genotypes and phenotypes, allelic frequencies in different populations, and clinical studies are discussed. The article also presents the current recommendations for pharmacogenetic testing in clinical practice and explores the drug, patient, research study design, regulatory, and practical issues that presently limit more widespread implementation.

Personalized medicine and genomics: challenges and opportunities in assessing effectiveness, cost-effectiveness, and future research priorities

Personalized medicine is health care that tailors interventions to individual variation in risk and treatment response. Although medicine has long strived to achieve this goal, advances in genomics promise to facilitate this process. Relevant to present-day practice is the use of genomic information to classify individuals according to disease susceptibility or expected responsiveness to a pharmacologic treatment and to provide targeted interventions. A symposium at the annual meeting of the Society for Medical Decision Making on 23 October 2007 highlighted the challenges and opportunities posed in translating advances in molecular medicine into clinical practice. A panel of US experts in medical practice, regulatory policy, technology assessment, and the financing and organization of medical innovation was asked to discuss the current state of practice and research on personalized medicine as it relates to their own field. This article reports on the issues raised, discusses potential approaches to meet these challenges, and proposes directions for future work. The case of genetic testing to inform dosing with warfarin, an anticoagulant, is used to illustrate differing perspectives on evidence and decision making for personalized medicine.

The promise and reality of pharmacogenetics in psychiatry

Existing psychotropic medications for the treatment of mental illnesses, including antidepressants, mood stabilizers, and antipsychotics, are clinically suboptimal. They are effective in only a subset of patients or produce partial responses, and they are often associated with debilitating side effects that discourage adherence. There is growing enthusiasm in the promise of pharmacogenetics to personalize the use of these treatments to maximize their efficacy and tolerability; however, there is still a long way to go before this promise becomes a reality. This article reviews the progress that has been made in research toward understanding how genetic factors influence psychotropic drug responses and the challenges that lie ahead in translating the research findings into clinical practices that yield tangible benefits for patients with mental illnesses.

Evaluating the utility of personal genomic information

In evaluating the utility of human genome-wide assays, the answer will differ depending on why the question is asked. For purposes of regulating medical tests, a restrictive sense of clinical utility is used, although it may be possible to have clinical utility without changing patient's outcomes and clinical utility may vary between patients. For purposes of using limited third party or public health resources, cost effectiveness should be evaluated in a societal rather than individual context. However, for other health uses of genomic information a broader sense of overall utility should be used. Behavioral changes and increased individual awareness of health-related choices are relevant metrics for evaluating the personal utility of genomic information, even when traditional clinical benefits are not manifested. In taking account of personal utility, cost effectiveness may be calculated on an individual and societal basis. Overall measures of utility (including both restrictive clinical measures and measures of personal utility) may vary significantly between individuals depending on potential changes in lifestyle, health awareness and behaviors, family dynamics, and personal choice and interest as well as the psychological effects of disease risk perception. That interindividual variation suggests that a more expansive overall measure of utility could be used to identify individuals who are more likely to benefit from personal genomic information as well as those for whom the risks of personal information may be greater than any benefits.

Evaluation of genetic tests for susceptibility to common complex diseases: why, when and how?

Recent research into the human genome has generated a wealth of scientific knowledge and increased both public and professional interest in the concept of personalised medicine. Somewhat unexpectedly, in addition to increasing our understanding about the genetic basis for numerous diseases, these new discoveries have also spawned a burgeoning new industry of 'consumer genetic testing'. In this paper, we present the principles learnt though the evaluation of tests for single gene disorders and suggest a comparable framework for the evaluation of genetic tests for susceptibility to common complex diseases. Both physicians and the general public will need to be able to assess the claims made by providers of genetic testing services, and ultimately policy-makers will need to decide if and when such tests should be offered through state funded healthcare systems.

Evidence-based medicine and practice guidelines: application to genetics

The Professional Practice and Guidelines Committee of the American College of Medical Genetics has the responsibility of overseeing the development of guidelines for the practice of clinical genetics. In the past, most, if not all, guidelines were primarily based on expert opinion. However, recently the goal has become to develop guidelines that are more evidence-based, or at least, to recognize the level of evidence available to the authors of these documents. This article reviews the challenges that are faced by geneticists who are charged with the development of practice guidelines.

Pharmacogenetics of selective serotonin reuptake inhibitors and associated adverse drug reactions

The selective serotonin reuptake inhibitors (SSRIs) have become one of the most widely prescribed classes of drugs. They are relatively safe for the pharmacologic treatment of various psychiatric disorders; however, certain patients cannot tolerate some adverse drug reactions associated with this drug class. In addition, clinicians currently have no way to predict who will respond appropriately to a given SSRI, and the paradigm of trial and error is especially distressing for patients with mental illness. Pharmacogenetic association studies may provide insight into which genetic polymorphisms might be clinically relevant for individualizing pharmacotherapeutic regimens. Thus, we reviewed and summarized the literature regarding the pharmacogenomics of SSRI-associated adverse drug reactions. This growing body of knowledge may inform subsequent design of pharmacogenetic studies with respect to adverse drug reactions. As we appreciate the many pharmacologic mechanisms related to adverse drug reactions and gain polymorphic functional data, we will have opportunities to refine hypotheses for future pharmacogenetic association analyses.

Application of pharmacogenomics to clinical problems in depression

The goal of this article is to review the literature for evidence supporting an association between polymorphisms within drug target genes and clinical outcomes for treating depression, with a purpose to identify a research area having the most promising potential to be introduced into clinical settings, and thus, discussing the perspectives of genotyping in antidepressant therapy. A total of 67 articles were identified. Polymorphic sites within the serotonin transporter gene promoter, 5-HTTLPR, were the most studied polymorphisms. All except three articles were designed as cohort studies. The other three articles included two meta-analyses and one decision-analytic model. The main finding from these meta-analyses was that the l variant was associated with a better response to selective serotonin reuptake inhibitors. The main conclusion from the decision-analytic model study was that performing genetic testing before prescribing antidepressant treatment may lead to greater numbers of patients experiencing remission early in treatment. Clinical outcomes of genotyping this polymorphism were evaluated by improvement of depression score, odds ratio and absolute risk reduction.

The Scientific Foundation for personal genomics: recommendations from a National Institutes of Health-Centers for Disease Control and Prevention multidisciplinary workshop

The increasing availability of personal genomic tests has led to discussions about the validity and utility of such tests and the balance of benefits and harms. A multidisciplinary workshop was convened by the National Institutes of Health and the Centers for Disease Control and Prevention to review the scientific foundation for using personal genomics in risk assessment and disease prevention and to develop recommendations for targeted research. The clinical validity and utility of personal genomics is a moving target with rapidly developing discoveries but little translation research to close the gap between discoveries and health impact. Workshop participants made recommendations in five domains: (1) developing and applying scientific standards for assessing personal genomic tests; (2) developing and applying a multidisciplinary research agenda, including observational studies and clinical trials to fill knowledge gaps in clinical validity and utility; (3) enhancing credible knowledge synthesis and information dissemination to clinicians and consumers; (4) linking scientific findings to evidence-based recommendations for use of personal genomics; and (5) assessing how the concept of personal utility can affect health benefits, costs, and risks by developing appropriate metrics for evaluation. To fulfill the promise of personal genomics, a rigorous multidisciplinary research agenda is needed.

Delivered dose: a drug-centric phenotype for chemotherapy dose individualization

It is pointed out that genotype-based approaches are unlikely to be effective at dose individualization. Delivered dose, which refers to the amount of drug delivered to the point of action to be measured by quantitative imaging techniques, is a drug-centric phenotype that separates pharmacokinetic effects from pharmacodynamic effects. Delivered dose serves as a midway measurable numeric parameter between drug administration and therapy outcome. One potential way to reduce chemotherapy outcome variation is to individualize prescribed drug so that uniform delivered dose is achieved across the patient population.

Genetic evaluation of cardiomyopathy--a Heart Failure Society of America practice guideline

Substantial progress has been made recently in understanding the genetic basis of cardiomyopathy. Cardiomyopathies with known genetic cause include hypertrophic (HCM), dilated (DCM), restrictive (RCM), arrhythmogenic right ventricular dysplasia/cardiomyopathy (ARVD/C) and left ventricular noncompaction (LVNC). HCM, DCM, and RCM have been recognized as distinct clinical entities for decades, whereas ARVD/C and LVNC are relative newcomers to the field. Hence the clinical and genetic knowledge for each cardiomyopathy varies, as do the recommendations and strength of evidence.

Clinical use of pharmacogenomic tests in 2009

Pharmacogenomics is a new field where testing an individual can define either a risk status for an adverse event, or the rate of metabolism of a drug. This is achieved by the categorisation of the enzyme activity or documenting genetic polymorphisms of a metabolising enzyme. The best example of risk status assessment is the recent finding that HLA-B typing a person can predict whether they are at risk of a severe skin reaction from the drug abacavir. Those patients showing HLA-B*5701, who are being considered for abacavir therapy, can be prevented from developing potentially toxic epidermal necrosis (TEN) or Stevens-Johnson Syndrome by avoiding abacavir. The evidence for HLA-B typing for allopurinol and carbamazepine has also been described. Most other pharmacogenomic tests are of drug metabolising enzymes, which can either be assessed using "probe" drugs and measuring a ratio of parent drug to metabolite, or, by genetic testing for polymorphisms of the genes. In practice, testing is usually done by molecular testing, but this typically does not detect all polymorphisms. This article briefly reviews the evidence for the utilisation of pharmacogenomics for antidepressant drugs, tamoxifen, codeine, warfarin, azathioprine, clopidogrel, omeprazole, tacrolimus and irinotecan. There are few pharmacogenomics tests being carried out in practice, as there has not been a wide appreciation of their use, and only limited evidence exists for many individual drugs. It is expected that utilisation will increase as more evidence becomes available and there is a wider understanding of the existing evidence by the medical profession.

Pharmacogenetic testing in schizophrenia and posttraumatic stress disorder

Genotyping patients prior to beginning psychiatric pharmacological therapy can serve to inform practitioners as to each patient's likelihood of therapeutic response and their relative risk of experiencing toxicity and other adverse side effects from certain drugs. Such information could arm physicians with the knowledge they need to make appropriate drug and dosing decisions and avoid the lengthy trial-and-error process with which they are faced today. This article describes the current state of pharmacogenetic testing in schizophrenia and posttraumatic stress disorder.

The evidence dilemma in genomic medicine

An ongoing dilemma in genomic medicine is balancing the need for scientific innovation with appropriate evidence thresholds for moving technology into practice. The current low threshold allows unsubstantiated technologies to enter into practice, with the potential to overwhelm the health system. Alternatively, establishing an excessively high threshold for evidence could slow the integration of genomics into practice and present disincentives for investing in research and development. Also, variable coverage and reimbursement policies can lead to differential access to technology, exacerbating health disparities. There is an urgent need for a collaborative process for appropriate transition of genomic discoveries from research to practice.

Abacavir hypersensitivity: a model system for pharmacogenetic test adoption

A pharmacogenetic marker for abacavir hypersensitivity is rapidly being incorporated into routine medical practice following demonstration of strong clinical utility in pivotal clinical studies. As one of the few pharmacogenetic markers that have crossed from research tools to clinical adoption and utilization, the abacavir hypersensitivity pharmacogenetic marker provides a great model for demonstration of factors that are critical to successful pharmacogenetic test adoption. Several examples of novel diagnostic test implementation are reviewed with focus on factors that are critical to translation into clinical practice. Other pharmacogenetic markers that have not yet been integrated into routine clinical care are discussed and reasons for their lack of acceptance are suggested.

DNA microarray technology in the clinical environment: the AmpliChip CYP450 test for CYP2D6 and CYP2C19 genotyping

INTRODUCTION

An important technological advance in genetic testing is the DNA microarray, which allows for the simultaneous testing of thousands of DNA sequences. The AmpliChip CYP450 Test employs this microarray technology for cytochrome P450 (CYP) 2D6 and CYP2C19 genotyping. Isoenzymes encoded by these genes are responsible for the metabolism of many widely prescribed drugs. The objectives of this study were to identify CYP2D6 and CYP2C19 alleles and phenotypes in a psychiatric patient population in Kentucky, and to describe practical issues associated with DNA microarray technology.

METHODS

A total of 4,532 psychiatric patients were recruited from three state hospitals in Kentucky. Whole blood, buccal swabs, or saliva samples were genotyped with the AmpliChip CYP450 Test to derive a predicted phenotype.

RESULTS

In this cohort, the overall prevalence of CYP2D6 poor metabolizers was 7.6% (95% CI 7%, 8.3%), 8.2% in the Caucasians (95% CI 7.4%, 9.%) and 1.8% in the African Americans (95% CI 0.9%, 3.5%). The overall prevalence of CYP2D6 ultrarapid metabolizers was 1.5% (95% CI 1.2%, 1.9%), 1.5% in the Caucasians (95% CI 1.1%, 1.9%) and 2.0% in the African Americans (95% CI 1.1%, 3.7%). The overall prevalence of CYP2C19 poor metabolizers was 2.0% (95% CI 1.8%, 2.7%), 2.2% in Caucasians (95% CI 1.6%, 2.5%) and 4.0% in African Americans (95% CI 2.6%, 6.1%).

CONCLUSION

We also propose a numeric system for expression of CYP2D6 and CYP2C19 enzyme activity to aid clinicians in determining treatment strategy for patients receiving therapeutics that are metabolized by the CYP2D6 or CYP2C19 gene products.

Pharmacogenomics: the promise of personalized medicine for CNS disorders

This review focuses first on the concept of pharmacogenomics and its related concepts (biomarkers and personalized prescription). Next, the first generation of five DNA pharmacogenomic tests used in the clinical practice of psychiatry is briefly reviewed. Then the possible involvement of these pharmacogenomic tests in the exploration of early clinical proof of mechanism is described by using two of the tests and one example from the pharmaceutical industry (iloperidone clinical trials). The initial attempts to use other microarray tests (measuring RNA expression) as peripheral biomarkers for CNS disorders are briefly described. Then the challenge of taking pharmacogenomic tests (compared to drugs) into clinical practice is explained by focusing on regulatory oversight, the methodological/scientific issues concerning diagnostic tests, and cost-effectiveness issues. Current information on medicine-based evidence and cost-effectiveness usually focuses on average patients and not the outliers who are most likely to benefit from personalized prescription. Finally, future research directions are suggested. The future of 'personalized prescription' in psychiatry requires consideration of pharmacogenomic testing and environmental and personal variables that influence pharmacokinetic and pharmacodynamic drug response for each individual drug used by each patient.

The Evaluation of Genomic Applications in Practice and Prevention (EGAPP) Initiative: methods of the EGAPP Working Group

The Evaluation of Genomic Applications in Practice and Prevention (EGAPP) Initiative, established by the National Office of Public Health Genomics at the Centers for Disease Control and Prevention, supports the development and implementation of a rigorous, evidence-based process for evaluating genetic tests and other genomic applications for clinical and public health practice in the United States. An independent, non-federal EGAPP Working Group (EWG), a multidisciplinary expert panel selects topics, oversees the systematic review of evidence, and makes recommendations based on that evidence. This article describes the EGAPP processes and details the specific methods and approaches used by the EWG.

The current landscape for direct-to-consumer genetic testing: legal, ethical, and policy issues

This review surveys the developing market for direct-to-consumer (DTC) genetic tests and examines the range of companies and tests available, the regulatory landscape, the concerns raised about DTC testing, and the calls for enhanced oversight. We provide a comparative overview of the situation, particularly in the United States and Europe, by exploring the regulatory frameworks for medical devices and clinical laboratories. We also discuss a variety of other mechanisms such as general controls on advertising and consumer law mechanisms.

Pharmacogenomic biomarker information in drug labels approved by the United States food and drug administration: prevalence of related drug use

STUDY OBJECTIVES

To review the labels of United States Food and Drug Administration (FDA)-approved drugs to identify those that contain pharmacogenomic biomarker information, and to collect prevalence information on the use of those drugs for which pharmacogenomic information is included in the drug labeling.

DESIGN

Retrospective analysis.

DATA SOURCES

The Physicians' Desk Reference Web site, Drugs@FDA Web site, and manufacturers' Web sites were used to identify drug labels containing pharmacogenomic information, and the prescription claims database of a large pharmacy benefits manager (insuring > 55 million individuals in the United States) was used to obtain drug utilization data.

MEASUREMENTS AND MAIN RESULTS

Pharmacogenomic biomarkers were defined, FDA-approved drug labels containing this information were identified, and utilization of these drugs was determined. Of 1200 drug labels reviewed for the years 1945-2005, 121 drug labels contained pharmacogenomic information based on a key word search and follow-up screening. Of those, 69 labels referred to human genomic biomarkers, and 52 referred to microbial genomic biomarkers. Of the labels referring to human biomarkers, 43 (62%) pertained to polymorphisms in cytochrome P450 (CYP) enzyme metabolism, with CYP2D6 being most common. Of 36.1 million patients whose prescriptions were processed by a large pharmacy benefits manager in 2006, about 8.8 million (24.3%) received one or more drugs with human genomic biomarker information in the drug label.

CONCLUSION

Nearly one fourth of all outpatients received one or more drugs that have pharmacogenomic information in the label for that drug. The incorporation and appropriate use of pharmacogenomic information in drug labels should be tested for its ability to improve drug use and safety in the United States.

Public health genomics: translating obesity genomics research into population health benefits

We examine how a public health genomics framework can be used to move genomic discoveries into clinical and public health practice for obesity prevention and treatment. There are four phases of translational research: T1: discovery to candidate health application; T2: health application to evidence-based practice guidelines; T3: practice guidelines to health practice; and T4: practice to population health impact. Types of multidisciplinary research and knowledge synthesis needed for each phase, as well as the importance of developing and disseminating evidence-based guidelines, are discussed. Because obesity genomics research is mostly in the discovery phase or in the very early phases of translation (T1), the authors present this framework to illustrate the range of translation activities needed to move genomic discoveries in obesity to actual applications that reduce the burden of obesity at the population level.

Increased carrier prevalence of deficient CYP2C9, CYP2C19 and CYP2D6 alleles in depressed patients referred to a tertiary psychiatric hospital

OBJECTIVE

This study compared the types and carrier prevalences of clinically significant DNA polymorphisms in the cytochrome P450 (CYP450) genes CYP2C9, CYP2C19 and CYP2D6 in major depressive disorder patients with a control group of nonpsychiatrically ill, medical outpatients.

METHOD

We conducted a case-control study using 73 psychiatric outpatients diagnosed with depression and referred to a tertiary center, The Institute of Living (Hartford, CT, USA), for treatment resistance or intolerable side-effects to psychotropic drugs. The controls were 120 cardiovascular patients from Hartford Hospital being treated for dyslipidemia but otherwise healthy and not psychiatrically ill. DNA typing to detect polymorphisms in the genes CYP2C9, CYP2C19 and CYP2D6 was accomplished with the Tag-It™ mutation detection assay and the Luminex xMAP^® system.

RESULTS

The percentage of individuals in psychiatric versus control groups with two wild-type alleles for CYP2C9, CYP2C19 and CYP2D6 genes, were 50 versus 74% (p < 0.001), 71 versus 73% (not statistically significant) and 36 versus 43% (trend, p < 0.2), respectively. Within the psychiatric population, 57% of individuals were carriers of non-wild-type alleles for 2-3 genes, compared with 36% in the control population (p < 0.0001). The balance, 43% in the psychiatric population and 64% in the control, were carriers of non-wild-type alleles for none or one gene.

CONCLUSIONS

These findings reveal that clinically relevant CYP2C9 polymorphisms occur more frequently in depressed psychiatric patients than in nonpsychiatric controls. The same trend was found for polymorphisms in the CYP2D6 gene. We found a significant cumulative metabolic deficiency in the psychiatric population for combinations of the CYP2C9, CYP2C19 and CYP2D6 genes. The significant enrichment of CYP2C9-deficient alleles in the psychiatric population validates a previously reported association of this gene with the risk for depression disorders. The high prevalence of carriers with deficient and null alleles suggests that CYP450 DNA typing may play a role in the management of psychiatric patients at tertiary care institutions.