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The interface of preclinical evaluation with clinical testing of antiepileptic drugs: role of pharmacogenomics and pharmacogenetics.

Despite the release of eight antiepileptic drugs (AEDs) during the last decade, the incidence of pharmacoresistant epilepsy has changed relatively little. Predicting efficacy and safety of AEDs in people with epilepsy from acute seizure models in rodents is difficult and risky. It is becoming increasingly clear that genetic polymorphisms play an integral role in variability in both antiepileptic drug pharmacokinetics and pharmacodynamics. The publication of the human genome and increasing sophisticated and powerful genetic tools offers new methods for screening drugs and predicting deadly idiosyncratic side effects. In this review the use of pharmacogenomic and pharmacokinetic techniques in the development and monitoring of antiepileptic drug therapy is reviewed. Genetic techniques have the potential of identifying novel drug targets, predicting drug response, and identifying individuals at risk for serious idosyncratic reactions.

Animals↗

A public health approach to pharmacogenomics and gene-based diagnostic tests.

While the human genome project is likely to lead to fundamental changes in our understanding of disease causation and our ability to screen for disease predisposition and treatment responsiveness, the current healthcare system is not properly aligned to ensure the proper use of these advances. As the pace of genetic technology development increases and new pharmacogenetic drugs and gene-based diagnostic tests increasingly impact providers, patients, health plans, payers and employers, it will be crucial to develop an evidence-based framework by which to evaluate these new tests and treatments. In order to increase the level of evidence available and allow for informed decisions in the face of strong marketing and advocacy forces, the authors suggest the development of one (or more) large clinical networks with the purpose of systematically evaluating the clinical effectiveness of new genomic applications, including pharmaceuticals and gene-based diagnostic tests, in 'real world' settings.

Evidence-Based Medicine↗

Measuring the value of pharmacogenomics.

Pharmacogenetics and pharmacogenomics offer the potential of developing DNA-based tests to help maximize drug efficacy and enhance drug safety. Major scientific advances in this field have brought us to the point where such tests are poised to enter more widespread clinical use. However, many questions have been raised about whether such tests will be of significant value, and how to assess this. Here, we review the application of economics-based resource-allocation frameworks to assess the value of pharmacogenomics, and the findings so far. We then develop a resource-allocation framework for assessing the potential value of pharmacogenomic testing from a population perspective, and apply this framework to the example of testing for variant alleles of CYP2D6, an important drug-metabolizing enzyme. This review provides a framework for analysing the value of pharmacogenomic interventions, and suggests where further research and development could be most beneficial.

Humans↗

Pharmacogenomic genotyping methodologies.

"Personalized medicine" based on an individual's genetic makeup is slowly becoming a reality as pharmacogenomics moves from the research setting to the clinical laboratory. Concordance studies between genotype and phenotype have shown that inherited mutations in several key drug-metabolizing enzymes, such as cytochrome P450 ( CYP ) 2D6 , 2C9 , and 2C19 , result in several distinct phenotypes that lead to different individual responses following drug administration. One of the major driving forces behind pharmacogenomics and its ability to be used effectively are the technologies that are available. A beneficial genotyping test must identify most or all of the mutations that have a significant impact on the expression or function of drug-metabolizing enzymes, transporter proteins, and/or drug receptors. Selection of the appropriate technology will be based on several issues, including prior knowledge of the mutation/polymorphism, sensitivity/specificity, sample requirements, and cost. Since the future volume of pharmacogenomic testing is anticipated to be large, automation of pharmacogenomics will also become increasingly important. This paper provides an overview of current technologies available for assessing polymorphisms on a small- to large-scale basis.

Alleles↗

deCODE genetics, Inc.

deCODE genetics, Inc. has compiled the world's most comprehensive collection of population data on genealogy, genotypes and phenotypes. This combination of resources provides an effective system for identifying key genes linked to common diseases and to the regulation of drug response. deCODE has successfully mapped genes in over 25 common complex diseases and isolated genes in eight of these. The methodology used to map these genes is based upon the company's genealogical database of the Icelandic population, which enables deCODE scientists to efficiently conduct population- and genome-wide linkage studies to identify key genetic factors involved in phenotypes ranging from diseases to drug response. In its growing pharmacogenomics program, deCODE has combined this linkage approach with high-throughput expression profiling to develop accurate tests that can predict individual responsiveness to virtually any drug of interest. deCODE is applying its unrivaled discovery capabilities to bring to market new drugs, DNA-based diagnostic products and pharmacogenomic tests. The company believes that such tests will play a crucial role in delivering personalized medicine - contributing to the development of more effective means of diagnosing and treating disease by matching each patient with the most suitable drug.

Chromosome Mapping↗

The role of cost-effectiveness analysis in the era of pharmacogenomics.

The broad availability of genetic information and technologies heralds an era when practitioners will utilise genomic testing to individualise patients' care. Pharmacogenomics uses a spectrum of approaches to explore the association of genetic variation with drug efficacy or toxicity. Investigators have described a broad array of genetic polymorphisms that confer inter-individual differences in drug response. Pharmacogenomics offers the potential to improve drug effectiveness, reduce adverse drug reactions and provide cost-effective care. However, it has had little impact on current clinical practice and the economic implications of pharmacogenomics remain unclear. Assessing the incremental cost effectiveness of a pharmacogenomic strategy involves examination of factors associated with the genotype of interest, the genomic test, the disease state and the treatment. A pharmacogenomic strategy is likely to be cost effective when: (i) the polymorphism under consideration is prevalent in the population and has a high degree of penetrance; (ii) genetic testing is highly sensitive and specific, and less costly alternative tests that could be used to individualise therapy are not readily available; (iii) the disease state involves outcomes with significant morbidity or mortality if left untreated; and (iv) the treatment involves significant outcomes and/or costs that can be impacted by genotype-individualised therapy. We foresee pharmacogenomic applications being particularly relevant for drugs: with a narrow therapeutic index or a high degree of variability in inter-individual response; where there are limitations in current methods for monitoring their adverse effects and treatment responses; and where there are few alternative treatment options. Because of the characteristics of chemotherapeutic agents and the severity of clinical outcomes in cancer, oncology appears to be one of the most appropriate disease areas for the application of pharmacogenomics. We have developed a framework which can assist researchers, pharmacists, physicians, and policy makers in evaluating the implications of specific strategies, and identifying when formal cost-effectiveness analyses should be conducted to quantitatively evaluate the benefits of pharmacogenomics.

Cost-Benefit Analysis↗

ExonHit Therapeutics.

ExonHit Therapeutics' mission is to be the leader in the application of alternative RNA splicing to the discovery and development of therapeutics and diagnostics for cancer and neurodegenerative diseases. The most advanced drugs in the Company's pipeline are treatments for amyotropic lateral sclerosis. One of these drugs entered Phase II trials in October 2002 and the other is planned for Phase I trials in 2003. Compounds for treating cancer are currently in the preclinical stage. ExonHit is also engaged in the discovery of molecular pharmacogenomic and diagnostic tests derived from RNA splicing events. ExonHit has established alliances with leading pharmaceutical and diagnostics companies, accelerating the R&D programs of its partners. The Company intends to license its pipeline of high-value drugs (after Phase IIb clinical trials) and diagnostics to these and other global partners.

Exons↗

Health benefits of antiviral therapy for mild chronic hepatitis C: randomised controlled trial and economic evaluation.

OBJECTIVES: To determine whether combined therapy with interferon-alpha and ribavirin was more effective and cost-effective than no treatment for patients with mild chronic hepatitis C. DESIGN: A multicentre, randomised, controlled, non-blinded trial assessed the efficacy of combination therapy. A Markov model used these efficacy data combined with data on transition probabilities, costs and health-related quality of life (HRQoL) to assess the lifetime cost-effectiveness of the intervention. SETTING: A multicentre NHS setting. PARTICIPANTS: Treatment-naive, adult patients with histologically mild chronic hepatitis C (Ishak necroinflammatory scores <4 and fibrosis scores <3 on liver biopsy). INTERVENTIONS: Patients were randomised to receive interferon-alpha and ribavirin for 48 weeks or no treatment (control). MAIN OUTCOME MEASURES: The primary outcome measure was the proportion of patients having a sustained virological response (SVR), measured at 6 months after cessation of therapy. Secondary outcome measures were: the ability of early phase kinetics to predict the eventual outcome of treating mild disease; HRQoL measured using the Short Form 36 and EuroQol (5 Dimensions) questionnaires, and the cost per quality-adjusted life-year (QALY) of interferon-alpha and ribavirin for mild disease compared with no treatment. RESULTS: In the treatment group, 32 out of 98 patients (33%) achieved an SVR. Patients infected with genotype 1 had a lower SVR than those infected with genotype non-1 (18% versus 49%, p = 0.02). No patients who failed to achieve a 2-log drop in viral load at 12 weeks achieved an SVR. HRQoL fell during treatment and rose with treatment cessation. For patients having an SVR there were modest improvements in HRQoL at 6 months post-treatment. The mean cost per QALY gained was 4535 pounds sterling for 40-year-old patients with genotype non-1 and 25,188 pounds sterling for patients with genotype 1. For patients with genotype 1 aged 65, providing interferon-alpha and ribavirin for mild disease led to fewer QALYs gained, and a mean cost per QALY of 53,017 pounds sterling. The model using efficacy estimates from the literature, showed that the cost per QALY gained from providing pegylated interferon alpha-2b and ribavirin at a mild stage rather than a moderate stage was 7821 pounds sterling for patients with genotype non-1 and 28,409 pounds sterling for patients with genotype 1. CONCLUSIONS: Based on the evidence collected in this study, interferon-alpha and ribavirin treatment for mild chronic hepatitis C patients is in general cost-effective at the 30,000 pounds sterling per QALY threshold previously used by policy-makers in the NHS. For patients with chronic hepatitis C aged 65 or over with genotype 1, antiviral treatment at a mild stage does not appear cost-effective. Further research is required on the cost-effectiveness of pegylated interferon and ribavirin, in particular the intervention's long-term impact on HRQoL and health service costs requires further evaluation. Further research is also needed to develop predictive tests, based on pharmacogenomics, that can identify those cases most likely to respond to antiviral therapy. Liver biopsy before treatment no longer appears justified apart from for older patients (aged 65 or over) with genotype 1. However, further research should monitor the impact this strategy would have on costs and outcomes.

Adult↗

[Ethics, politics, and rights in pharmacogenomics].

The article focuses in three aspects. Firstly, distinctions are drawn between pharmacogenetic testing and other types of genetic test, and the advantages of pharmacogenomics for individuals and society generally are discussed. Secondly, the article examines some of the ethical problems raised by research in and clinical aspects of pharmacogenomics. Thirdly and lastly, a number of risk potentially associated with this new technology are discussed.

Clinical Trials as Topic↗

Preparing for the revolution--pharmacogenomics and the clinical lab.

Pharmacogenomics seeks to apply the field of genomics to improve the efficacy and safety of therapeutics. Sinmply put, pharmacogenomics is genetic-based testing to determine patient therapy. Interestingly, the clinical lab has rarely been discussed within the context of pharmacogenomics. Since clinical labs fill a key role in drug development it is important that they are included in pharmacogenomic discussions. Currently, clinical labs assist pharmaceutical sponsors in preclinical pharmacogenetic testing. In the future, clinical labs will be looked to for genetic test development and validation, and high-throughput genotyping of patients in clinical trials and routine testing. Clinical labs are an essential link in the chain of pharmacogenomic drug development, a fact which must be recognised by both the labs themselves and the industry as a whole.

Drug Industry↗

Pharmacogenomics and children: meeting the ethical challenges.

Pharmacogenomic research promises to permit the development and delivery of safer and more effective drugs. If children are to receive these benefits, as justice would demand that they should, children must be included in trials that assess the impact of genetic variation, changing patterns of gene expression over time, and the effects of administering drugs. The ethical and legal challenges to conducting the necessary research include concerns about vulnerability and issues of consent, the scientific validity of the studies and the larger policy question of priority setting. Proposed strategies for ensuring the appropriate conduct of this research include analysis of the ethics based on risks and harms rather than presence or absence of a disorder, the development of model substrates to conduct physiological testing more safely, and the consideration of the disposition and impact of individual study results. With appropriate study, ultimately the use of pharmacogenomic testing can become available for children in the clinical setting.

Child↗

HIV resistance testing in the USA--a model for the application of pharmacogenomics in the clinical setting.

Although there is debate about how and when the medical community will readily adopt pharmacogenomics into clinical practice, HIV genotyping has become an integral part of AIDS patient management in the USA since 1996. Genotyping for HIV-1 drug resistance serves as a paradigm for the way pharmacogenomics is likely to be introduced into patient care. This review discusses the unique role that HIV-1 genotype testing plays in identifying resistance in patients and how that information is used to modify therapy selection and impact the progression of disease. In addition, the important issues relating to reimbursement and the cost-effectiveness of genotyping are also discussed.

Acquired Immunodeficiency Syndrome↗

Human immunodeficiency virus type 1 pharmacogenomics in clinical practice: relevance of HIV-1 drug resistance testing (Part 2).

Throughout most of the past century, physicians could offer patients no treatments for infections caused by viruses. The experience with treatment of infection by human immunodeficiency virus (HIV) has changed the way healthcare workers deal with viral infections and has triggered a growing rate of discovery and use of antiviral agents, the first fruits of the expanding genomics revolution. HIV treatment also provides an informative paradigm for pharmacogenomics because control of infection and its consequences is limited by the development of viral drug resistance and by host factors. This report summarizes studies published to date on the significance of testing of HIV-1 resistance to antiretroviral drugs. The only Food and Drug Administration-approved kit is commercially available through Visible Genetics, Inc., for HIV drug resistance testing by genotypic sequencing. Genotyping sequencing alone is most likely an adequate test to assist in the therapeutic decision-making process in cases of previous regimen failure, treatment-naïve patients in areas of high prevalence of transmitted resistant virus, and pregnant women. However, in exceptional cases of highly complex mutation patterns and extensive cross-resistance, it may be useful to obtain a phenotype test, because that result may more easily identify drugs to which the virus is least resistant. There are no published clinical trial results on the usefulness of the so-called virtual phenotype over genotypic sequencing alone. The paradigm of viral pharmacogenomics in the form of HIV genotypic sequencing has been not only useful to the treatment of other viral diseases but also important to the real-life implementation of the growing discipline of genomics or molecular medicine. The application of this paradigm to the thousands of potential therapeutic targets that have become available through the various human genome projects will certainly gradually change the landscape of diagnosis and management of many diseases, including cancer.

Antiviral Agents↗

Human immunodeficiency virus type 1 pharmacogenomics in clinical practice: relevance of HIV-1 drug resistance testing (Part 1).

Throughout most of the past century, physicians could offer patients no treatments for infections caused by viruses. The experience with treatment of infection by human immunodeficiency virus (HIV) has changed the way healthcare workers deal with viral infections and has triggered a growing rate of discovery and use of antiviral agents, the first fruits of the expanding genomics revolution. HIV treatment also provides an informative paradigm for pharmacogenomics because control of infection and its consequences is limited by the development of viral drug resistance and by host factors. This report summarizes studies published to date on the significance of testing of HIV-1 resistance to antiretroviral drugs. The only Food and Drug Administration-approved kit for HIV drug resistance testing by genotypic sequencing is commercially available through Visible Genetics, Inc. Genotyping sequencing alone is most likely an adequate test to assist in the therapeutic decision-making process for previous regimen failure, for treatment-naïve patients in areas of high prevalence of transmitted resistant virus, and for pregnant women. However, in exceptional cases of highly complex mutation patterns and extensive cross-resistance, it may be useful to obtain a phenotype test, because that result may more easily identify drugs to which virus is least resistant. There are no published clinical trials results on the usefulness of the so-called virtual phenotype over genotypic sequencing alone. Not only has the paradigm of viral pharmacogenomics in the form of HIV genotypic sequencing been useful in treating other viral diseases, but it is also important to the real-life implementation of the growing discipline ofgenomics or molecular medicine. The application of this paradigm to the thousands of potential therapeutic targets that have become available through the various human genome projects will certainly gradually change the landscape of diagnosis and management of many diseases, including cancer.

Anti-HIV Agents↗

Pharmacogenomics and nutrigenomics: synergies and differences.

The success of the Human Genome Project and the spectacular development of broad genomics tools have catalyzed a new era in both medicine and nutrition. The terms pharmacogenomics and nutrigenomics are relatively new. Both have grown out of their genetic forbears as large-scale genomics technologies have been developed in the last decade. The aim of both disciplines is to individualize or personalize medicine and food and nutrition, and ultimately health, by tailoring the drug or the food to the individual genotype. This review article provides an overview of synergies and differences between these two potentially powerful science areas. Individual genetic variation is the common factor on which both pharmacogenomics and nutrigenomics are based. Each human is genetically (including epigenetics) unique and phenotypically distinct. One of the expectations of both technologies is that a wide range of gene variants and related single-nucleotide polymorphism will be identified as to their importance in health status, validated and incorporated into genotype based strategies for the optimization of health and the prevention of disease. Pharmacogenomics requires rigorous genomic testing that will be regulated and analyzed by professionals and acted on by medical practitioners. As further information is obtained on the importance of the interaction of food and the human genotype in disease prevention and health, pharmacogenomics can provide an opportunity driver for nutrigenomics. As we move from disease treatment to disease prevention, the two disciplines will become more closely aligned.

Food, Organic↗

UGT1A1 genotype testing for irinotecan: A guideline developed by the UK Centre of Excellence in Regulatory Science and Innovation in Pharmacogenomics (CERSI-PGx).

Irinotecan, a topoisomerase I inhibitor, is available as both non-pegylated and pegylated formulations. The non-pegylated formulation is licensed for use in advanced colorectal cancer either in combination with other agents or as monotherapy. However, it is also used off-label across a range of gastrointestinal malignancies and in rare malignancies such as glioblastoma and sarcomas. The pegylated formulation is licensed for use as combination therapy in adult patients with metastatic pancreatic adenocarcinoma. Irinotecan is hydrolysed to its active metabolite, SN-38, which is predominantly inactivated by the enzyme uridine diphosphate glucuronosyltransferase UGT1A1. UGT1A1 is encoded by the gene UGT1A1, which is polymorphically expressed, with allele frequencies varying across populations. Poor metabolizers carry two variants that reduce UGT1A1 enzyme expression or activity, leading to increased risk of irinotecan toxicity. Any patient who is about to be prescribed irinotecan for an epithelial malignancy should have pharmacogenetic testing, to identify clinically relevant UGT1A1 variants, where testing is available. Irinotecan dose should be reduced by 30% at Cycle 1 treatment in poor metabolizers for all indications, with doses titrated thereafter based on tolerability and neutrophil counts. The lack of evidence precludes us from making any recommendation for rare malignancies such as sarcomas. Our guideline is consistent with other international pharmacogenetics prescribing guidelines. This guideline is grounded in the latest evidence but cannot account for all individual factors relevant to patient care. Therefore, prescribers must conduct a thorough assessment of each patient's risk-benefit profile, ensuring that therapy is optimized to maximize benefits while minimizing potential harms.

Humans↗

Pharmacogenomics.

The discovery of the human genome and subsequent expansion of proteomics research combined with emerging technologies such as functional imaging, biosensors and sophisticated computational biology are producing unprecedented changes in today's healthcare. The expanding knowledge of the molecular basis of cancer has shown that significant differences in gene expression patterns can guide therapy not only for neoplastic conditions, but also for a variety of diseases including inflammatory disorders, cardiovascular disease and neurodegenerative processes. As a result, the fields of pharmacogenetics and pharmacogenomics have emerged as potential new testing platforms for the individualized management of patients. An individual's response to a drug is the complex interaction of both genetic and non-genetic factors. Genetic variants in the drug target itself, disease pathway genes, or drug metabolizing enzymes may all be used as predictors of drug efficacy or toxicity. In oncology, the SNP technology has focused on detecting the predisposition for cancer, predicting of toxic responses to drugs and selecting the best individual and combinations of anti-cancer drugs. Pharmacogenomics involves the application of whole genome technologies (e.g., gene and protein expression data) for the prediction of the sensitivity or resistance of an individual's disease to a single or group of drugs. Genomic microarrays and transcriptional profiling have the ability to generate hundreds of thousands of data points requiring sophisticated and complex information systems necessary for accurate and useful data analysis. This technique has generated a wealth of new information in the fields of leukemia/lymphoma, and solid tumor classification and prediction of metastasis, drug and biomarker target discovery and pharmacogenomic drug efficacy testing.

Drug Resistance, Neoplasm↗