The clinical effectiveness and cost-effectiveness of testing for cytochrome P450 polymorphisms in patients with schizophrenia treated with antipsychotics: a systematic review and economic evaluation

The effect of CYP2D6 variation on antipsychotic-induced hyperprolactinaemia: a systematic review and meta-analysis

Hyperprolactinemia is a known adverse drug reaction to antipsychotic treatment. Antipsychotic blood levels are influenced by cytochrome P450 enzymes, primarily CYP2D6. Variation in CYP450 genes may affect the risk of antipsychotic-induced hyperprolactinemia. We undertook a systematic review and meta-analysis to assess whether CYP2D6 functional genetic variants are associated with antipsychotic-induced hyperprolactinemia. The systematic review identified 16 relevant papers, seven of which were suitable for the meta-analysis (n = 303 participants including 134 extreme metabolisers). Participants were classified into four phenotype groups as poor, intermediate, extensive, and ultra-rapid metabolisers. A random effects meta-analysis was used and Cohen's d calculated as the effect size for each primary study. We found no significant differences in prolactin levels between CYP2D6 metabolic groups. Current evidence does not support using CYP2D6 genotyping to reduce risk of antipsychotic-induced hyperprolactinemia. However, statistical power is limited. Future studies with larger samples and including a range of prolactin-elevating drugs are needed.

A pharmacogenetic intervention for the improvement of the safety profile of antipsychotic treatments

Antipsychotic drugs fail to achieve adequate response in 30-50% of treated patients and about 50% of them develop severe and lasting side effects. Treatment failure results in poorer prognosis with devastating repercussions for the patients, carers and broader society. Our study evaluated the clinical benefits of a pharmacogenetic intervention for the personalisation of antipsychotic treatment. Pharmacogenetic information in key CYP polymorphisms was used to adjust clinical doses in a group of patients who started or switched treatment with antipsychotic drugs (PharmG+, N = 123), and their results were compared with those of a group of patients treated following existing clinical guides (PharmG-, N = 167). There was no evidence of significant differences in side effects between the two arms. Although patients who had their antipsychotic dose adjusted according to CYPs polymorphisms (PharmG+) had a bigger reduction in side effects than those treated as usual (PharmG-), the difference was not statistically significant (p > 0.05 for all comparisons). However, PharmG+ patients treated with CYP2D6 substrates that were carriers of CYP2D6 UMs or PMs variants showed a significantly higher improvement in global, psychic and other UKU side effects than PharmG- patients (p = 0.02, p = 0.05 and p = 0.01, respectively). PharmG+ clozapine treated patients with CYP1A2 or CYP2C19 UM and PMs variants also showed higher reductions in UKU scores than PharmG- clozapine patients in general. However, those differences were not statistically significant. Pharmacogenetic interventions may improve the safety of antipsychotic treatments by reducing associated side effects. This intervention may be particularly useful when considering treatment with antipsychotics with one major metabolic pathway, and therefore more susceptible to be affected by functional variants of CYP enzymes.

Tardive dyskinesia update: the syndrome

Tardive dyskinesia is a common iatrogenic neurological and neurobehavioural syndrome associated with the use of antidopaminergic medication, especially antipsychotics. Prior to the introduction of the newer antipsychotics in the 1990s, it was one of the major areas of psychiatric research but interest waned as the new drugs were reputed to have a reduced liability to extrapyramidal adverse effects in general, a claim now discredited by numerous pragmatic research studies. Early small-scale short-term prevalence studies were presented as evidence to support the assumption that patients on the newer drugs did indeed have a lower prevalence of tardive dyskinesia but recent large-scale review of studies with patients exposed for longer suggest that things have not changed. This article presents a clinical overview of a complex and varied syndrome in terms of its phenomenology, epidemiology and risk factors; a companion article will consider treatment. This overview aims to highlight tardive dyskinesia once again, especially to practitioners who have trained in an environment where this was considered mainly in historical terms.

LEARNING OBJECTIVES

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DECLARATION OF INTEREST

None.

Clinical risk factors for the development of tardive dyskinesia

BACKGROUND

Tardive dyskinesia (TD) is a severe condition that can affect almost 1 out of 4 patients on current or previous antipsychotic treatment, including both first-generation antipsychotics (FGAs) and second-generation antipsychotics (SGAs). While two novel vesicular monoamine transporter inhibitors, deutetrabenazine and valbenazine, have shown acute efficacy for TD, the majority of patients do not remit, and TD appears to recur once treatment is withdrawn. Hence, prevention of TD remains a crucial goal.

METHODS

We provide a clinically oriented overview of risk factors for TD, dividing them into patient-, illness- and treatment-related variables, as well as nonmodifiable and modifiable factors.

RESULTS

Unmodifiable patient-related and illness-related risk factors for TD include older age, female sex, white and African descent, longer illness duration, intellectual disability and brain damage, negative symptoms in schizophrenia, mood disorders, cognitive symptoms in mood disorders, and gene polymorphisms involving antipsychotic metabolism and dopamine functioning. Modifiable comorbidity-related and treatment-related factors include diabetes, smoking, and alcohol and substance abuse, FGA vs SGA treatment, higher cumulative and current antipsychotic dose or antipsychotic plasma levels, early parkinsonian side effects, anticholinergic co-treatment, akathisia, and emergent dyskinesia.

DISCUSSION

Clinicians using dopamine antagonists need to consider risk factors for TD to minimize TD and its consequences.

The effect of CYP1A2 gene polymorphism on the metabolism of theophylline

This aim of the study was to investigate the effect of CYP1A2 gene polymorphism on the metabolism of theophylline in minority and Han nationality. A total of 50 cases of Han (Han group) and 50 minority nationalities (ethnic groups) treated with theophylline were selected for the study. The genotype and allele frequencies of the two groups of CYP1A2 gene, G-3113A and G-3860A, were compared to determine the rate of theophylline clearance. The results showed that there was no significant difference in the concentration of the homeostasis and the rate of the theophylline removal rate (P>0.05). There was no significant difference in the genotype and allele frequencies of the CYP1A2 gene, G-3113A and G-3860A apolymorphic site. This study employed a logarithm to determine theophylline clearance in order to correlate it with the normal distribution. The results showed that the theophylline clearance of the two groups of CYP1A2 G-3113A gene loci A allele carriers (AA+GA genotype) was significantly lower than that of the G allele carriers (GG genotype), and a significant difference between the groups was identified (P<0.05). There was no significant difference in the theophylline clearance rates in the two groups for the CYP1A2 gene, G-3860A apolymorphic site (P>0.05). Compared to the GG genotype of the CYP1A2 gene, the G-3113A site AA and GA genotype patients had a low clearance rate in the theophylline, whereas there was no correlation between teh genotypes of the CYP1A2 gene, G-3860A and the rate of theophylline clearance.

No Effect of Dose Adjustment to the CYP2D6 Genotype in Patients With Severe Mental Illness

Background: The CYP2D6 enzyme is involved in the metabolism of numerous psychopharmacological drugs. Guidelines recommend how to adjust the dose of medication based on the CYP2D6 genotype. Aims: To evaluate the effect of dose adjustment to the CYP2D6 genotype and phenotype, in patients with severe mental illness (SMI) already receiving psychopharmacological treatment. Methods: A total of 269 psychiatric patients (on the island Curaçao) receiving antipsychotic treatment were genotyped for CYP2D6. Of these, 45 patients were included for dose adjustment according to the clinical guideline of the Royal Dutch Association for the Advancement of Pharmacy, i.e., 17 CYP2D6 poor metabolizers, 26 intermediate metabolizers, and 2 ultrarapid metabolizers. These 45 patients were matched for age, gender, and type of medication with a control group of 41 patients who were CYP2D6 extensive metabolizers (i.e., with a normal CYP2D6 function). At baseline and at 4 months after dose adjustment, subjective experience, psychopathology, extrapyramidal side-effects, quality of life, and global functioning were assessed in these two groups. Results: At baseline, there were no differences between the groups regarding the prescribed dosage of antipsychotics, the number of side-effects, psychiatric symptoms, global functioning, or quality of life. After dose adjustment, no significant improvement in these parameters was reported. Conclusion: In psychiatric patients with SMI already receiving antipsychotic treatment, dose adjustment to the CYP2D6 genotype or phenotype according to the guidelines showed no beneficial effect. This suggests that dose adjustment guidelines are currently not applicable for patients already using antipsychotics. ClinicalTrials.gov: Cost-effectiveness of CYP2D6 and CYP2C19 Genotyping in Psychiatric Patients in Curacao; Identifier: NCT02713672; https://clinicaltrials.gov/ct2/show/NCT02713672?term=CYP2D6&rank=5.

A cost-effectiveness analysis of maternal CYP2D6 genetic testing to guide treatment for postpartum pain and avert infant adverse events

Mothers with a CYP2D6 ultrarapid metabolizer phenotype may expose their infants to risk of adverse events when taking codeine while breastfeeding, by producing more of the active metabolite, morphine. Pharmacogenetic testing may be a valuable tool to identify such mothers, but testing can be costly. The objective of the study was to determine the incremental costs of genotyping to avert neonatal adverse events during maternal pharmacotherapy. A cost-effectiveness analysis, using a decision model, was performed with a hypothetical cohort of prenatal subjects. Parameter estimates, costs and ranges for sensitivity analyses were ascertained from the literature and expert opinion. Sensitivity analyses were conducted to assess the robustness of the results. Probabilistic sensitivity analysis revealed an incremental cost-effectiveness (ICER) of $10 433 (Canadian dollars) for genotyping compared to no genotyping per adverse event averted. Results were sensitive to hospital admission costs. The ICER was lower when evaluating only subjects having caesarean deliveries or those from ethnic populations known to have a high prevalence of ultra-rapid metabolizers. Although genotyping to guide pharmacotherapy was not cost saving, the cost to avert an infant adverse event may represent good value for money in specific populations. With a growing demand for personalized medicine, these findings are relevant for decision makers, clinicians and patients.

CYP2D6 and CYP2C19 genotyping in psychiatric patients on psychotropic medication in the former Dutch Antilles

AIM

This study was aimed to asses the prevalence of CYP2D6 and CYP2C19 polymorphisms in psychiatric patients and in volunteers from Dutch caribbean origin.

METHODS

In total, 435 individuals were genotyped for CYP2D6 and CYP2C19. Of these, 269 were psychiatric patients on psychotropic medication, living in Curaçao and 166 were volunteers from the Dutch Caribbean population.

RESULTS

No differences in prevalence of alleles were found.

CONCLUSION

Although prevalence of alleles appeared to be very different from African and Caucasian populations, the distribution into predicted phenotypes shows an equal distribution as in Caucasians.

Evidence synthesis to inform model-based cost-effectiveness evaluations of diagnostic tests: a methodological review of health technology assessments

BACKGROUND

Evaluations of diagnostic tests are challenging because of the indirect nature of their impact on patient outcomes. Model-based health economic evaluations of tests allow different types of evidence from various sources to be incorporated and enable cost-effectiveness estimates to be made beyond the duration of available study data. To parameterize a health-economic model fully, all the ways a test impacts on patient health must be quantified, including but not limited to diagnostic test accuracy.

METHODS

We assessed all UK NIHR HTA reports published May 2009-July 2015. Reports were included if they evaluated a diagnostic test, included a model-based health economic evaluation and included a systematic review and meta-analysis of test accuracy. From each eligible report we extracted information on the following topics: 1) what evidence aside from test accuracy was searched for and synthesised, 2) which methods were used to synthesise test accuracy evidence and how did the results inform the economic model, 3) how/whether threshold effects were explored, 4) how the potential dependency between multiple tests in a pathway was accounted for, and 5) for evaluations of tests targeted at the primary care setting, how evidence from differing healthcare settings was incorporated.

RESULTS

The bivariate or HSROC model was implemented in 20/22 reports that met all inclusion criteria. Test accuracy data for health economic modelling was obtained from meta-analyses completely in four reports, partially in fourteen reports and not at all in four reports. Only 2/7 reports that used a quantitative test gave clear threshold recommendations. All 22 reports explored the effect of uncertainty in accuracy parameters but most of those that used multiple tests did not allow for dependence between test results. 7/22 tests were potentially suitable for primary care but the majority found limited evidence on test accuracy in primary care settings.

CONCLUSIONS

The uptake of appropriate meta-analysis methods for synthesising evidence on diagnostic test accuracy in UK NIHR HTAs has improved in recent years. Future research should focus on other evidence requirements for cost-effectiveness assessment, threshold effects for quantitative tests and the impact of multiple diagnostic tests.

Economic Evaluation of Pharmacogenetic Tests in Patients Subjected to Renal Transplantation: A Review of Literature

Renal transplantation is the treatment of choice for the patients with end-stage renal failure. Genetic factors, among others, can influence variability in response to immunosuppressive drugs. Nowadays, due to restrictive health resources, the question arises whether routine pharmacogenetic analyses should be done in the renal transplant recipients or not. The aim of this literature review was to present the up-to-date information considering the economic feasibility of pharmacogenetic testing in patients subjected to renal transplantation. The organization United Network for Organ Sharing in the US estimated that total costs per renal transplant concerning these analyses were $334,300 in 2014. Pharmacogenetic testing prior to treatment initiation could be helpful to predict and assess treatment response and the risks for adverse drug reactions. This kind of testing before treatment initiation seems to be one of the most promising applications of pharmacokinetics. Although pharmacogenetic tests were found to be a cost-effective or cost-saving strategy in many cases, some authors represent another opinion. However, if the real costs of renal transplantation are recognized, the application of these tests in the standard daily practice could be considered more realistic, which additionally emphasizes the importance of future studies assessing their cost effectiveness.

New drug developments in psychosis: Challenges, opportunities and strategies

All currently approved drugs for schizophrenia work mainly by dopaminergic antagonism. While they are efficacious for psychotic symptoms, their efficacy is limited for negative symptoms and cognitive deficits which underlie the substantive disability in this illness. Recent insights into the biological basis of schizophrenia, especially in relation to non-dopaminergic mechanisms, have raised the efforts to find novel and effective drug targets, though with relatively little success thus far. Potential impediments to novel drug discovery include the continued use of symptom based disease definitions which leads to etiological and pathophysiological heterogeneity, lack of valid preclinical models for drug testing, and design limitations in clinical trials. These roadblocks can be addressed by (i) characterizing trans-diagnostic, translational pathophysiological dimensions as potential treatment targets, (ii) efficiency, accountability and, transparency in approaches to the clinical trials process, and (iii) leveraging recent advances in genetics and in vitro phenotypes. Accomplishing these goals is urgent given the significant unmet needs in the pharmacological treatment of schizophrenia. As this happens, it is imperative that clinicians employ optimal dosing, measurement-based care, and other best practices in utilizing existing treatments to optimize outcomes for their patients today.

Enabling personalized cancer medicine decisions: The challenging pharmacological approach of PBPK models for nanomedicine and pharmacogenomics (Review)

The existing tumor heterogeneity and the complexity of cancer cell biology critically demand powerful translational tools with which to support interdisciplinary efforts aiming to advance personalized cancer medicine decisions in drug development and clinical practice. The development of physiologically based pharmacokinetic (PBPK) models to predict the effects of drugs in the body facilitates the clinical translation of genomic knowledge and the implementation of in vivo pharmacology experience with pharmacogenomics. Such a direction unequivocally empowers our capacity to also make personalized drug dosage scheme decisions for drugs, including molecularly targeted agents and innovative nanoformulations, i.e. in establishing pharmacotyping in prescription. In this way, the applicability of PBPK models to guide individualized cancer therapeutic decisions of broad clinical utility in nanomedicine in real-time and in a cost-affordable manner will be discussed. The latter will be presented by emphasizing the need for combined efforts within the scientific borderlines of genomics with nanotechnology to ensure major benefits and productivity for nanomedicine and personalized medicine interventions.

Economic evaluations of personalized medicine: existing challenges and current developments

Personalized medicine, with the aim of safely, effectively, and cost-effectively targeting treatment to a prespecified patient population, has always been a long-time goal within health care. It is often argued that personalizing treatment will inevitably improve clinical outcomes for patients and help achieve more effective use of health care resources. Demand is increasing for demonstrable evidence of clinical and cost-effectiveness to support the use of personalized medicine in health care. This paper begins with an overview of the existing challenges in conducting economic evaluations of genetics- and genomics-targeted technologies, as an example of personalized medicine. Our paper illustrates the complexity of the challenges faced by these technologies by highlighting the variations in the issues faced by diagnostic tests for somatic variations, generally referring to genetic variation in a tumor, and germline variations, generally referring to inherited genetic variation in enzymes involved in drug metabolic pathways. These tests are typically aimed at stratifying patient populations into subgroups on the basis of clinical effectiveness (response) or safety (avoidance of adverse events). The paper summarizes the data requirements for economic evaluations of genetics and genomics-based technologies while outlining that the main challenges relating to data requirements revolve around the availability and quality of existing data. We conclude by discussing current developments aimed to address the challenges of assessing the cost-effectiveness of genetics and genomics-based technologies, which revolve around two central issues that are interlinked: the need to adapt available evaluation methods and identifying who is responsible for generating evidence for these technologies.

Human cytochrome P450 and personalized medicine

Personalized medicine has become a hot topic ascribed to the development of Human Genome Project. And currently, bioinformatics methodology plays an essential role in personal drug design. Here in this review we mainly focused on the basic introduction of the SNPs of human drug metabolic enzymes and their relationships with personalized medicine. Some common bioinformatics analysis methods and latest progresses and applications in personal drug design have also been discussed. Thus bioinformatics studies on SNPs of human CYP450 genes will contribute to indicate the most possible genes that are associated with human diseases and relevant therapeutic targets, identify and predict the drug efficacy and adverse drug response, investigate individual gene specific properties and then provide personalized and optimal clinic therapies.

Through a glass darkly: economics and personalised medicine

Personalised medicine and pharmacogenetic-test-guided treatment strategies will be of increasing importance in the future, both in terms of healthcare provision and evaluation. It is well recognised that significant variability exists in the response of patients to drugs resulting from genetic or biological variations; however, we are only now gradually becoming aware of the complexities involved. Enormous variability occurs in the risk-benefit ratio that will be experienced by each individual patient as a consequence of their overall genetic make-up. Although not a panacea, enhanced scientific knowledge of the genetic basis for such variability offers the potential for a more 'tailored' approach to prescribing in the future, making it more closely attuned to the needs of the individual patient. Such 'personalised' medicine has the potential to revolutionise care provision in a manner that provides a range of challenges to current structures and processes of 'conventional' healthcare delivery. The aim of this paper is to outline such challenges and analyse potential ways in which they may be addressed in the future. It provides non-expert readers with a non-technical case study of the complexities inherent in the evaluation of a pharmacogenetic-test-guided treatment strategy from a health economic perspective. Wherever possible, technical issues have been minimised; however, references are provided for readers who wish to enhance their knowledge of the pharmacological basis of the case study of cytochrome P450 test-guided treatment. The case study aims simply to illustrate the approach and difficulties encountered in the health economic evaluation of complex pharmacogenetic technologies. Such technologies present a range of new and complex issues which have crucial implications for health economists attempting to obtain an accurate assessment of the 'value' of the technology in clinical practice in an array of patient subgroups. Personalised medicine is the future and this paper highlights how pharmaceutical manufacturers, clinicians, regulators and other stakeholders must all play their part in the inevitable and accelerating move into this complex and uncertain future.

A phase II randomized trial evaluating gefitinib intercalated with pemetrexed/platinum chemotherapy or pemetrexed/platinum chemotherapy alone in unselected patients with advanced non-squamous non-small cell lung cancer

Current pemetrexed/platinum chemotherapy does not produce a satisfactory therapeutic response in advanced lung cancer patients. The aim of this study was to determine whether the administration of gefitinib, a tyrosine kinase inhibitor (TKI), intercalated with pemetrexed/platinum could improve the efficacy in chemotherapy-naïve patients with advanced non-squamous NSCLC without subsequent gefitinib maintenance therapy. Treatment-naïve patients with stage IIIB or IV NSCLC were randomly assigned to receive pemetrexed (500 mg/m (2) d1) and either cisplatin (75 mg/m (2) d1) or carboplatin (AUC = 5 d1) plus gefitinib (250 mg/d on days 3 to 16 of a 3-week cycle) (PC-G) or pemetrexed-platinum (PC) alone. Randomization was stratified according to the tobacco smoking status and EGFR mutational status of the patients. The primary endpoint was the non-progression rate (NPR) at 12 weeks. Secondary endpoints included progression-free survival (PFS), overall response rate (ORR), overall survival (OS), and biosafety. The NPR at 12 weeks was 84.5% for the PC-G treatment arm and 83.1% for the PC treatment arm (P = 0.87). Median PFS was 7.9 months for the PC-G arm and 7.0 months for the PC arm (P = 0.57). The ORR was 50.0% for the PC-G arm and 47.4% for the PC arm (P = 0.78). Median survival was 25.4 mo for the PC-G arm and 20.8 mo for the PC arm (P = 0.54). The incidence of adverse events was similar between the two treatment arms, except for a higher incidence of skin rash with PC-G. Predefined subgroup analyses demonstrated that PC-G significantly increased the PFS compared with the PC regimen in patients with EGFR mutations (P = 0.017). Although gefitinib intercalated with pemetrexed/platinum chemotherapy did not improve the NPR at 12 weeks compared with chemotherapy, an improvement in the PFS for the intercalated treatment arm was seen in the subgroup of patients with EGFR mutations.

Pharmacogenetics of antipsychotics

OBJECTIVE

During the past decades, increasing efforts have been invested in studies to unravel the influence of genetic factors on antipsychotic (AP) dosage, treatment response, and occurrence of adverse effects. These studies aimed to improve clinical care by predicting outcome of treatment with APs and thus allowing for individualized treatment strategies. We highlight most important findings obtained through both candidate gene and genome-wide association studies, including pharmacokinetic and pharmacodynamic factors.

METHODS

We reviewed studies on pharmacogenetics of AP response and adverse effects published on PubMed until early 2012. Owing to the high number of published studies, we focused our review on findings that have been replicated in independent studies or are supported by meta-analyses.

RESULTS

Most robust findings were reported for associations between polymorphisms of the cytochrome P450 system, the dopamine and the serotonin transmitter systems, and dosage, treatment response, and adverse effects, such as AP-induced weight gain or tardive dyskinesia. These associations were either detected for specific medications or for classes of APs.

CONCLUSION

First promising and robust results show that pharmacogenetics bear promise for a widespread use in future clinical practice. This will likely be achieved by developing algorithms that will include many genetic variants. However, further investigation is warranted to replicate and validate previous findings, as well as to identify new genetic variants involved in AP response and for replication of existing findings.

The estimation of utility weights in cost-utility analysis for mental disorders: a systematic review

OBJECTIVE

To systematically review approaches and instruments used to derive utility weights in cost-utility analyses (CUAs) within the field of mental disorders and to identify factors that may have influenced the choice of the approach.

METHODS

We searched the databases DARE (Database of Abstracts of Reviews of Effects), NHS EED (National Health Service Economic Evaluation Database), HTA (Health Technology Assessment), and PubMed for CUAs. Studies were included if they were full economic evaluations and reported quality-adjusted life-years as the health outcome. Study characteristics and instruments used to estimate utility weights were described and a logistic regression analysis was conducted to identify factors associated with the choice of either the direct (e.g. standard gamble) or the preference-based measure (PBM) approach (e.g. EQ-5D).

RESULTS

We identified 227 CUAs with a maximum in 2009, 2010, and 2012. Most CUAs were conducted in depression, dementia, or psychosis, and came from the US or the UK, with the EQ-5D being the most frequently used instrument. The application of the direct approach was significantly associated with depression, psychosis, and model-based studies. The PBM approach was more likely to be used in recent studies, dementia, Europe, and empirical studies. Utility weights used in model-based studies were derived from only a small number of studies.

LIMITATIONS

We only searched four databases and did not evaluate the quality of the included studies.

CONCLUSIONS

Direct instruments and PBMs are used to elicit utility weights in CUAs with different frequencies regarding study type, mental disorder, and country.

Current methodological issues in the economic assessment of personalized medicine

There is a need for methodological scrutiny in the economic assessment of personalized medicine. In this article, we present a list of 10 specific issues that we argue pose specific methodological challenges that require careful consideration when designing and conducting robust model-based economic evaluations in the context of personalized medicine. Key issues are related to the correct framing of the research question, interpretation of test results, data collection of medical management options after obtaining test results, and expressing the value of tests. The need to formulate the research question clearly and be explicit and specific about the technology being evaluated is essential because various test kits can have the same purpose and yet differ in predictive value, costs, and relevance to practice and patient populations. The correct reporting of sensitivity/specificity, and especially the false negatives and false positives (which are population dependent), of the investigated tests is also considered as a key element. This requires additional structural complexity to establish the relationship between the test result and the consecutive treatment changes and outcomes. This process involves translating the test characteristics into clinical utility, and therefore outlining the clinical and economic consequences of true and false positives and true and false negatives. Information on treatment patterns and on their costs and outcomes, however, is often lacking, especially for false-positive and false-negative test results. The analysis can even become very complex if different tests are combined or sequentially used. This potential complexity can be handled by explicitly showing how these tests are going to be used in practice and then working with the combined sensitivities and specificities of the tests. Each of these issues leads to a higher degree of uncertainty in economic models designed to assess the added value of personalized medicine compared with their simple pharmaceutical counterparts. To some extent, these problems can be overcome by performing early population-level simulations, which can lead to the identification and collection of data on critical input parameters. Finally, it is important to understand that a test strategy does not necessarily lead to more quality-adjusted life-years (QALYs). It is possible that the test will lead to not only fewer QALYs but also fewer costs, which can be defined as "decremental" cost per QALYs. Different decision criteria are needed to interpret such results.

Reflections on market access for personalized medicine: recommendations for Europe

This article aims to provide an overview of the current literature focusing on the reimbursement of personalized medicine across the European Union. The article starts by describing types of perspectives that are possible (general public, patient, payer, provider, service commissioner, and policymaker). The description of perspectives also explains the importance of understanding the different possible decision criteria and processes from the various perspectives by taking into account budget constraints. The article then focuses on an example of personalized medicine, namely, the use of companion diagnostic-medicine combinations, to describe the role of reimbursement/payer agencies across the European Union to control the introduction and coverage of such companion diagnostic-medicine technologies. The article touches on the strategic challenges and the use of economic evidence to introduce personalized medicine from a health policy perspective. The article also draws on empirical studies that have explored patients' and clinicians' views of examples of personalized medicine to illustrate the challenges for developing patient-centered and timely health care services.

Personalized medicine in psychiatry: problems and promises

The central theme of personalized medicine is the premise that an individual's unique physiologic characteristics play a significant role in both disease vulnerability and in response to specific therapies. The major goals of personalized medicine are therefore to predict an individual's susceptibility to developing an illness, achieve accurate diagnosis, and optimize the most efficient and favorable response to treatment. The goal of achieving personalized medicine in psychiatry is a laudable one, because its attainment should be associated with a marked reduction in morbidity and mortality. In this review, we summarize an illustrative selection of studies that are laying the foundation towards personalizing medicine in major depressive disorder, bipolar disorder, and schizophrenia. In addition, we present emerging applications that are likely to advance personalized medicine in psychiatry, with an emphasis on novel biomarkers and neuroimaging.

Utility and adoption of CYP2D6 and CYP2C19 genotyping and its translation into psychiatric clinical practice

OBJECTIVE

To describe clinical utility and adoption of routinely offered CYP2D6 and CYP2C19 genotyping (CYP test) in daily clinical practice of a psychiatric centre.

METHOD

We described psychiatrists translations of CYP test results in patients with genotypes indicating poor or ultrarapid metabolizer status and treated with at least one CYP-dependent drug based on a retrospective review of medical records. Complementary, we used ethnographic participant observation and qualitative interviews to identify the barriers and incentives for the use of CYP test results.

RESULTS

The cohort study included 101 of 1932 cases genotyped between 2003 and 2009. In 53 of 101 cases, test results were addressed in medical records. The most frequent response was to monitor drug concentrations (23 cases), observe for adverse events (18 cases) and adjust dosage (13 cases). In 33 of 101 cases, results were mentioned in the discharge letter. The ethnographic study indicated a poor adoption of the CYP test in clinical praxis. Test results were lost in workflows and knowledge transfer between laboratory and clinician and were absent from clinical routines, treatment conferences and educational fora.

CONCLUSION

The CYP test has not gained foothold in clinical practice, and its potential clinical benefits are not utilized.

Prioritizing pharmacogenetic research: a value of information analysis of CYP2D6 testing to guide breast cancer treatment

OBJECTIVES

To demonstrate how value of information (VOI) analysis can be used to establish research priorities regarding the use of pharmacogenetic tests using CYP2D6 testing to select adjuvant hormonal therapy in early stage breast cancer as a case study.

METHODS

The following four treatment pathways are compared in a Markov model: tamoxifen treatment; CYP2D6 test and treat homozygous and heterozygous wild type patients (wt/wt; wt/*4) with tamoxifen and *4/*4 patients with anastrozole (HetTam); CYP2D6 test and treat homozygous wild type patients with tamoxifen and others with anastrozole (HomTam); and anastrozole treatment. Pharmacogenetic testing efficacy is estimated by synthesizing randomized controlled trial data comparing tamoxifen to anastrozole with observational data linking CYP2D6 genotype to tamoxifen outcomes.

RESULTS

In order of increasing effectiveness the comparators are tamoxifen, HetTam, HomTam, anastrozole. Health outcomes for test and treatment strategies are highly uncertain. Differences in comparator costs depend on assumptions made regarding anastrozole patent expiry. The expected value of a decision taken with perfect information is £69 to £106 million (pound sterling) for the United Kingdom depending on patent expiry assumptions and the acceptable cost-effectiveness threshold. The most valuable research (VOI £53-£82 million) elucidates the relationship between CYP2D6 genotype and tamoxifen effectiveness. It is uncertain whether values of other research designs would exceed their costs.

CONCLUSIONS

Retrospective analysis of one of the large adjuvant aromatase inhibitor trials is warranted to better understand any association between CYP2D6 genotype and tamoxifen outcomes. VOI approaches may be helpful for prioritising evidence needs and structuring coverage with evidence development agreements for pharmacogenetics.

Pharmacogenetics of response to antipsychotics in patients with schizophrenia

This review presents the findings of pharmacogenetic studies exploring the influence of gene variants on antipsychotic treatment response, in terms of both symptom improvement and adverse effects, in patients with schizophrenia. Despite numerous studies in the field, replicating findings across different cohorts that include subjects of different ethnic groups has been challenging. It is clear that non-genetic factors have an important contribution to antipsychotic treatment response. Differing clinical, demographic and environmental characteristics of the cohorts studied have added substantial complexity to the interpretation of the positive and negative findings of many studies. Pharmacogenomic genome-wide investigations are beginning to yield interesting data although they have failed to replicate the most robust findings of candidate gene studies, and are limited by the sample size, especially given the need for studying homogeneous cohorts. Most of the studies conducted on cohorts treated with single antipsychotics have investigated clozapine, olanzapine or risperidone response. These studies have provided some of the most replicated associations with treatment efficacy. Serotonergic system gene variants are significantly associated with the efficacy of clozapine and risperidone, but may have less influence on the efficacy of olanzapine. Dopamine D3 receptor polymorphisms have been more strongly associated with the efficacy of clozapine and olanzapine, and D2 genetic variants with the efficacy of risperidone. Serotonin influences the control of feeding behaviour and has been hypothesized to have a role in the development of antipsychotic-induced weight gain. Numerous studies have linked the serotonin receptor 2C (5-HT2C) -759-C/T polymorphism with weight gain. The leptin gene variant, -2548-G/A, has also been associated with weight gain in several studies. Pharmacogenetic studies support the role of cytochrome P450 enzymes and dopamine receptor variants in the development of antipsychotic-induced movement disorders, with a contribution of serotonergic receptors and other gene variants implicated in the mechanism of action of antipsychotics. Clozapine-induced agranulocytosis has been associated with polymorphisms in the major histocompatibility complex gene (HLA).

Pharmacogenomics of antipsychotics efficacy for schizophrenia

Central nervous system disorders are the third greatest health problem in developed countries, and schizophrenia represents some of the most disabling ailments in young individuals. There is an abuse and/or misuse of antipsychotics, and recent advances in pharmacogenomics pose new challenges for the clinical management of this complex disorder. Schizophrenia is a multi-factorial/polygenic complex disorder in which hundreds of different genes are potentially involved, leading to the phenotypic expression of the disease in conjunction with epigenetic and environmental phenomena. Consequently, structural and functional genomic changes induce proteomic and metabolomic defects associated with the disease phenotype. Disease-related genomic profiles and genetic variants in genes involved in drug metabolism are responsible for drug efficacy and safety. About 20% of Caucasians are defective in CYP2D6 enzymes, which participate in the metabolism of 25-30% of central nervous system drugs. Approximately 40% of antipsychotics are substrates of CYP2D6 enzymes, 23% are substrates of CYP3A4, and 18% are substrates of CYP1A2. In order to achieve a mature discipline of pharmacogenomics of schizophrenia it would be effective to accelerate: (i) the education of physicians and the public in the use of genomic screening in daily clinical practice; (ii) the standardization of genetic testing for major categories of drugs; (iii) the validation of pharmacogenomic procedures according to drug category and pathology; (iv) the regulation of ethical, social, and economic issues; and (v) the incorporation of pharmacogenomic procedures of drugs in development and drugs on the market in order to optimize therapeutics.

Genetics of tardive dyskinesia

Tardive dyskinesia (TD) is one of the most serious adverse side effects of antipsychotic drugs and is an important topic of pharmacogenetic studies. Since there is a genetic susceptibility for developing this adverse reaction, and given that it is hard to predict its development prior to or during the early period of medication, the genetic study of TD is a promising research topic that has a direct clinical application. Moreover, such studies would improve our understanding of the genetic mechanism(s) underlying abnormal dyskinetic movement. A substantial number of case-control association studies of TD have been performed, with numbers of studies focusing on the genes involved in antipsychotic drug metabolism, such as those for cytochrome P450 (CYP) and oxidative stress related genes as well as various neurotransmitter related genes. These studies have produced relatively consistent though controversial findings for certain polymorphisms such as CYP2D6*10, DRD2 Taq1A, DRD3 Ser9Gly, HTR2A T102C, and MnSOD Ala9Val. Moreover, the application of the genome-wide association study (GWAS) to the susceptibility of TD has revealed certain associated genes that previously were never considered to be associated with TD, such as the rs7669317 on 4q24, GLI2 gene, GABA pathway genes, and HSPG2 gene. Although a substantial number of genetic studies have investigated TD, many of the positive findings have not been replicated or are inconsistent, which could be due to differences in study design, sample size, and/or subject ethnicity. We expect that more refined research will be performed in the future to resolve these issues, which will then enable the genetic prediction of TD and clinical application thereof.

Nanomedicine and personalized medicine toward the application of pharmacotyping in clinical practice to improve drug-delivery outcomes

Recent technological advances in nanomedicine and nanotechnology in parallel with knowledge accumulated from the clinical translation of disease- and drug-related genomic data have created fertile ground for personalized medicine to emerge as the new direction in diagnosis and drug therapy. To this end, the development of sophisticated nano-based systems for targeted drug delivery, along with the advent of pharmacogenomics, moves the drug-prescription process toward pharmacotyping, e.g., the individualized adjustment of drug selection and dosage. However, the clinical validity and utility of pharmacogenomic testing must be demonstrated by cost-effectiveness analysis and establishment of clinical-practice reimbursement codes. Within this framework, and to achieve major benefits for all patients worldwide, a multidisciplinary scientific and technological infrastructure has to be organized in the healthcare system to address better the issues affecting regulatory environment, clinical pharmacology guidelines, education, bioethics and genomics data dissemination.

FROM THE CLINICAL EDITOR

Individualized pharmacotyping, patient and disease-specific delivery of drugs, combining nanotechnology and pharmagenomics-based approaches would result in much more specific and efficient treatment of a variety of illnesses. While this clearly is one of the main cornerstones of individualized medicine; the cost effective integration of this complex technology is far from trivial, as discussed in details in this opinion paper.

Future Trends in the Pharmacogenomics of Brain Disorders and Dementia: Influence of APOE and CYP2D6 Variants

About 80% of functional genes in the human genome are expressed in the brain and over 1,200 different genes have been associated with the pathogenesis of CNS disorders and dementia. Pharmacogenetic studies of psychotropic drug response have focused on determining the relationship between variations in specific candidate genes and the positive and adverse effects of drug treatment. Approximately, 18% of neuroleptics are substrates of CYP1A2 enzymes, 40% of CYP2D6, and 23% of CYP3A4; 24% of antidepressants are substrates of CYP1A2 enzymes, 5% of CYP2B6, 38% of CYP2C19, 85% of CYP2D6, and 38% of CYP3A4; 7% of benzodiazepines are substrates of CYP2C19 enzymes, 20% of CYP2D6, and 95% of CYP3A4. 10-20% of Western populations are defective in genes of the CYP superfamily; and the pharmacogenomic response of psychotropic drugs also depends on genetic variants associated with dementia. Prospective studies with anti-dementia drugs or with multifactorial strategies have revealed that the therapeutic response to conventional drugs in Alzheimer’s disease is genotype-specific. The disease-modifying effects (cognitive performance, biomarker modification) of therapeutic intervention are APOE-dependent, with APOE-4 carriers acting as the worst responders (APOE-3/3 > APOE-3/4 > APOE-4/4). APOE-CYP2D6 interactions also influence the therapeutic outcome in patients with dementia.

Genomics and pharmacogenomics of schizophrenia

Schizophrenia (SCZ) is among the most disabling of mental disorders. Several neurobiological hypotheses have been postulated as responsible for SCZ pathogenesis: polygenic/multifactorial genomic defects, intrauterine and perinatal environment-genome interactions, neurodevelopmental defects, dopaminergic, cholinergic, serotonergic, gamma-aminobutiric acid (GABAergic), neuropeptidergic and glutamatergic/N-Methyl-D-Aspartate (NMDA) dysfunctions, seasonal infection, neuroimmune dysfunction, and epigenetic dysregulation. SCZ has a heritability estimated at 60-90%. Genetic studies in SCZ have revealed the presence of chromosome anomalies, copy number variants, multiple single-nucleotide polymorphisms of susceptibility distributed across the human genome, aberrant single nucleotide polymorphisms (SNPs) in microRNA genes, mitochondrial DNA mutations, and epigenetic phenomena. Pharmacogenetic studies of psychotropic drug response have focused on determining the relationship between variation in specific candidate genes and the positive and adverse effects of drug treatment. Approximately, 18% of neuroleptics are major substrates of CYP1A2 enzymes, 40% of CYP2D6, and 23% of CYP3A4; 24% of antidepressants are major substrates of CYP1A2 enzymes, 5% of CYP2B6, 38% of CYP2C19, 85% of CYP2D6, and 38% of CYP3A4; 7% of benzodiazepines are major substrates of CYP2C19 enzymes, 20% of CYP2D6, and 95% of CYP3A4. About 10-20% of Western populations are defective in genes of the CYP superfamily. Only 26% of Southern Europeans are pure extensive metabolizers for the trigenic cluster integrated by the CYP2D6+CYP2C19+CYP2C9 genes. The pharmacogenomic response of SCZ patients to conventional psychotropic drugs also depends on genetic variants associated with SCZ-related genes. Consequently, the incorporation of pharmacogenomic procedures both to drugs in development and drugs on the market would help to optimize therapeutics in SCZ and other central nervous system (CNS) disorders.

Elucidation of CYP2D6 genetic diversity in a unique African population: implications for the future application of pharmacogenetics in the Xhosa population

Genetic variation of the CYP2D6 gene has been associated with altered drug metabolism; however, limited studies have investigated CYP2D6 sequence diversity in African populations. We devised a CYP2D6 genotyping strategy to analyse the South African Xhosa population and genotype a Xhosa schizophrenia cohort, as CYP2D6 metabolises many antipsychotics and antidepressants. The entire CYP2D6 gene locus was sequenced in 15 Xhosa control individuals and the data generated were used to design a comprehensive genotyping strategy. Over 25 CYP2D6 alleles were genotyped in Xhosa controls and Xhosa schizophrenia patients using long-range PCR, DNA sequencing and single nucleotide primer extension analysis. Bioinformatic algorithms were used to predict the functional consequences of relevant mutations and samples were assigned CYP2D6 activity scores. A unique allele distribution was revealed and two rare novel alleles, CYP2D6*73 and CYP2D6*74, were identified. No significant differences in allele frequencies were detected between Xhosa controls and schizophrenia patients. This study provides i) comprehensive data on a poorly characterised population, ii) a valuable CYP2D6 genotyping strategy and iii) due to their unique genetic profile, provides the basis for pharmacogenetic intervention for Xhosa individuals.

Pharmacogenetics and psychoactive drug therapy: ready for the patient?

Psychiatry is one of the most promising areas for bringing pharmacogenomics to the patient. Psychiatric disorders such as depression and schizophrenia contribute significantly to worldwide morbidity and mortality. Forecasts rank depression second only to ischemic heart disease by 2020. In depression and schizophrenia, 30% to 50% of all patients do not respond sufficiently to the initial treatment regime. Genetic variability has been demonstrated to play an important role in the response to pharmacotherapy. Most data are available with regard to polymorphisms in the genes coding for drug-metabolizing enzymes and recommendations for the choice of personalized dosages based on genotyping results are available. Clinical outcome, in particular adverse effects, has been shown to correlate with the results from genotyping. Incorporating pharmacogenomics into clinical practice has, however, been slow and it is still not clear in which clinical situations genotyping should be performed and what the benefit of such procedures could be beyond therapeutic drug monitoring. Additionally, many studies in psychiatry focus on genetic variation in candidate genes of drug targets. However, despite promising reports, no clear recommendation can be given at present to perform such testing in clinical use.