Availability of pharmacogenomics-based prescribing information in drug package inserts for currently approved drugs

Analytical validation of GenoPharm a clinical genotyping open array panel of 46 pharmacogenes inclusive of variants unique to people of African ancestry

Pharmacogenomic testing may be used to improve treatment outcomes and reduce the frequency of adverse drug reactions (ADRs). Population specific, targeted pharmacogenetics (PGx) panel-based testing methods enable sensitive, accurate and economical implementation of precision medicine. We evaluated the analytical performance of the GenoPharm® custom open array platform which evaluates 120 SNPs across 46 pharmacogenes. Using commercially available reference samples (Coriell Biorepository) and in-house extracted DNA, we assessed accuracy, precision, and linearity of GenoPharm®. We then used GenoPharm® on 218 samples from two Southern African black populations and determined allele and genotype frequencies for selected actionable variants. Across all assays, the GenoPharm® panel demonstrated 99.5% concordance with the Coriell reference samples, with 98.9% reproducibility. We observed high frequencies of key genetic variants in people of African ancestry: CYP2B6*6 (0.35), CYP2C9*8, *11 (0.13, 0.03), CYP2D6*17 (0.21) and *29 (0.11). GenoPharm® open array is therefore an accurate, reproducible and sensitive test that can be used for clinical pharmacogenetic testing and is inclusive of variants specific to the people of African ancestry.

Pharmacogenetic information in Swiss drug labels - a systematic analysis

Implementation of pharmacogenetics (PGx) and individualization of drug therapy is supposed to obviate adverse drug reactions or therapy failure. Health care professionals (HCPs) use drug labels (DLs) as reliable information about drugs. We analyzed the Swiss DLs to give an overview on the currently available PGx instructions. We screened 4306 DLs applying natural language processing focusing on drug metabolism (pharmacokinetics) and we assigned PGx levels following the classification system of PharmGKB. From 5979 hits, 2564 were classified as PGx-relevant affecting 167 substances. 55% (n = 93) were classified as "actionable PGx". Frequently, PGx information appeared in the pharmacokinetics section and in DLs of the anatomic group "nervous system". Unstandardized wording, appearance of PGx information in different sections and unclear instructions challenge HCPs to identify and interpret PGx information and translate it into practice. HCPs need harmonization and standardization of PGx information in DLs to personalize drug therapies and tailor pharmaceutical care.

Emergence and Evolution of Pharmacogenetics and Pharmacogenomics in Clinical Pharmacy over the Past 40 Years

2006 marked the 40th year of publication for The Annals. Throughout its history, The Annals has provided important contributions to the development of clinical pharmacy. In 2007, we are continuing to publish articles reflecting on the history of clinical pharmacy through the eyes of practitioners, including those pioneering clinical pharmacy, as well as those whohave more recently entered the profession and a well-established specialty. In addition, we are presenting articles and editorials from the early history of The Annals that have given direction and shape to the practice of clinical pharmacy (see page 2042).

Incorporating Pharmacogenomics into Practice

The goal for this issue of the Journal of Pharmacy Practice is to provide an overview of pharmacogenomics and highlight research done in select therapeutic areas such as oncology, psychiatry, cardiology, and HIV, although pharmacogenomics is taking center stage in other therapeutic areas as well. At the root of all pharmacogenomic investigations is pharmacy, which is why it is so important for pharmacists to gain an understanding of this field and clinical applications of this science, particularly as it relates to their practice and their patients. Pharmacists are experts in pharmacokinetics and pharmacodynamics, and they therefore represent ideal health care professionals for incorporating pharmacogenomics into therapeutic drug monitoring. We are currently in a critical period of time in which pharmacists need to become engaged in the decision-making process regarding how best to implement pharmacogenomics into clinical practice. As part of this chapter, we will outline the role of the Human Genome Project and the Food and Drug Administration, both of which are instrumental to the advancement of pharmacogenomics. Lastly, we will be summarizing some of the barriers we still face regarding clinical applicability of this science and the potential role of genetic counselors in the incorporation of this science into clinical practice.

Comparing cytochrome P450 pharmacogenetic information available on United States drug labels and European Union Summaries of Product Characteristics

Regulatory agencies are increasing the pharmacogenomic information in their official drug labeling. However, despite the importance of regulatory harmonization, this implementation may not be running in parallel among major agencies. Comparing labeling of medicines approved by different agencies may identify gaps to solve. Our study compared the cytochrome P450 pharmacogenetic information included in the United States (US) Food and Drug Administration (FDA) drug labels and European Union (EU) Summaries of Product Characteristics (SmPCs). US labels presented significantly more specific pharmacogenetic subheadings (51 vs 26%), more prevalence and pharmacokinetic data for each metabolic phenotype (59 vs 25% and 82 vs 48%, respectively) and more applicable information about dose modifications required (25 vs 5%). Approximately 75% of the US labels evaluated scored higher on the overall quality than the analogous EU SmPCs, and this difference was not associated with the time since the EU SmPCs' last review. To enhance harmonization, regulatory agencies should simultaneously introduce the pharmacogenetic information in their drug labeling.

Improving the Efficiency and Quality of the Value Assessment Process for Companion Diagnostic Tests: The Companion test Assessment Tool (CAT)

BACKGROUND

Companion diagnostic tests (CDTs) have emerged as a vital technology in the effective use of an increasing number of targeted drug therapies. Although CDTs can offer a multitude of potential benefits, assessing their value within a health technology appraisal process can be challenging because of a complex array of factors that influence clinical and economic outcomes.

OBJECTIVE

To develop a user-friendly tool to assist managed care and other health care decision makers in screening companion tests and determining whether an intensive technology review is necessary and, if so, where the review should be focused to improve efficiency.

METHODS

First, we conducted a systematic literature review of CDT cost-effectiveness studies to identify value drivers. Second, we conducted key informant interviews with a diverse group of stakeholders to elicit feedback and solicit any additional value drivers and identify desirable attributes for an evidence review tool. A draft tool was developed based on this information that captured value drivers, usability features, and had a particular focus on practical use by nonexperts. Finally, the tool was pilot tested with test developers and managed care evidence evaluators to assess face-validity and usability. The tool was also evaluated using several diverse examples of existing companion diagnostics and refined accordingly.

RESULTS

We identified 65 cost-effectiveness studies of companion diagnostic technologies. The following factors were most commonly identified as value drivers from our literature review: clinical validity of testing; efficacy, safety, and cost of baseline and alternative treatments; cost and mortality of health states; and biomarker prevalence and testing cost. Stakeholders identified the following additional factors that they believed influenced the overall value of a companion test: regulatory status, actionability, utility, and market penetration. These factors were used to maximize the efficiency of the evidence review process. Stakeholders also stated that a tool should be easy to use and time efficient. Cognitive interviews with stakeholders led to minor changes in the draft tool to improve usability and relevance. The final tool consisted of 4 sections: (1) eligibility for review (2 questions), (2) prioritization of review (3 questions), (3) clinical review (3 questions), and (4) economic review (5 questions).

CONCLUSIONS

Although the evaluation of CDTs can be challenging because of limited evidence and the added complexity of incorporating a diagnostic test into drug treatment decisions, using a pragmatic tool to identify tests that do not need extensive evaluation may improve the efficiency and effectiveness of CDT value assessments.

An evaluation of pharmacogenomic information provided by five common drug information resources

INTRODUCTION

This study evaluated whether pharmacogenomic information contained in the Food and Drug Administration (FDA)-approved package inserts of sixty-five drugs was present in five drug information resources.

METHODS

The study searched for biomarkers from the FDA package inserts in 5 drug information sources: American Hospital Formulary Service Drug Information (AHFS), Facts & Comparisons 4.0 (Facts), ePocrates Online Free (ePocrates Free), Lexicomp Online (Lexicomp), and Micromedex 2.0. Each resource had the opportunity to present biomarker information for 65 drugs, a total of 325 opportunities. A binary system was used to indicate presence or absence of the biomarker information. A sub-analysis was performed on the 13 most frequently prescribed drugs in the United States.

RESULTS

Package insert biomarker information was available, on average, for 81.5% of the 65 FDA-listed drugs in 2011. Percent availability for the individual resources was: Lexicomp, 95.3%; Micromedex 2.0, 92.3%; Facts, 76.9%; AHFS, 75.3%; and ePocrates Free, 67.7%. The sub-analysis of the 13 top drugs showed Lexicomp and Micromedex 2.0 had the most mentions, 92.3%; ePocrates Free had the least, 53.8%.

CONCLUSION

The strongest resource for pharmacogenomic information was Lexicomp. The gap between Lexicomp and ePocrates Free is concerning. Clinicians would miss pharmacogenomic information 6.6 times more often in ePocrates Free than in Lexicomp.

IMPLICATIONS

Health sciences librarians should be aware of the variation in biomarker availability when recommending drug resources for licensing and use. Librarians can also use this study to encourage publishers to include pharmacogenomics information from the package insert as a minimum standard.

Screening for 392 polymorphisms in 141 pharmacogenes

Pharmacogenomics is the study of the association between inter-individual genetic differences and drug responses. Researches in pharmacogenomics have been performed in compliance with the use of several genotyping technologies. In this study, a total of 392 single-nucleotide polymorphisms (SNPs) located in 141 pharmacogenes, including 21 phase I, 13 phase II, 18 transporter and 5 modifier genes, were selected and genotyped in 150 subjects using the GoldenGate assay or the SNaPshot technique. These variants were in Hardy-Weinberg equilibrium (HWE) (P>0.05), except for 22 SNPs. Genotyping of the 392 SNPs revealed that the minor allele frequencies of 47 SNPs were <0.05, 105 SNPs were monomorphic and 22 variants were not in HWE. Also, based on previous studies, we predicted the association between the polymorphisms of certain pharmacogenes, such as cytochrome P450 2D6, cytochrome P450 2C9, vitamin K epoxide reductase complex, subunit 1, cytochrome P450 2C19, human leukocyte antigen, class I, B and thiopurine S-methyltransferase, and drug efficacy. In conclusion, our study demonstrated the allele distribution of SNPs in 141 pharmacogenes as determined by high-throughput screening. Our results may be helpful in developing personalized medicines by using pharmacogene polymorphisms.

Racial differences in attitudes toward personalized medicine

BACKGROUND/AIMS

Patient concerns regarding personalized medicine may limit its use. This study assesses racial differences in attitudes toward personalized medicine, evaluating variables that may influence these attitudes.

METHODS

A convenience sample of 190 adults (≥18 years) from an academic primary care practice was surveyed regarding awareness and acceptance of personalized medicine, plus concerns and benefits regarding its use. Logistic regressions predicting awareness, acceptance and concerns were performed, controlling for race, gender, marital status, education, children, internet use, and self-reported discrimination.

RESULTS

The sample was 35% non-Hispanic white (NHW) and 34.7% male. More NHW participants expressed acceptance of personalized medicine than non-Hispanic black (NHB) participants (94.4 vs. 81.9%, p = 0.0190). More NHBs were concerned about the use of genes without consent (57.3 vs. 20.6%, p < 0.0001), sharing genetic information without consent (65.0 vs. 35.6%, p < 0.0001), discrimination based on genes (62.4 vs. 34.3%, p = 0.0002), and lack of access due to cost (75.0 vs. 48.0%, p = 0.0002). In logistic regressions, NHBs (OR = 7.46, 95% CI = 3.04-18.32) and those self-reporting discrimination (OR = 2.87, 95% CI = 1.22-6.78) had more concerns about the misuse of genes and costs associated with personalized medicine.

CONCLUSION

Racial differences exist in attitudes toward personalized medicine and may be influenced by self-reported discrimination. Further study to understand factors influencing the acceptance of personalized medicine could help encourage its use.

Physician Awareness and Utilization of Food and Drug Administration (FDA)-Approved Labeling for Pharmacogenomic Testing Information

We surveyed 10,303 United States physicians on where they obtain pharmacogenomic testing information. Thirty-nine percent indicated that they obtained this from drug labeling. Factors positively associated with this response included older age, postgraduate instruction, using other information sources, regulatory approval/ recommendation of testing, reliance on labeling for information, and perception that patients have benefited from testing. Physicians use pharmacogenomic testing information from drug labeling, highlighting the importance of labeling information that is conducive to practice application.

Clinical delivery of pharmacogenetic testing services: a proposed partnership between genetic counselors and pharmacists

One of the basic questions in the early uses of pharmacogenetic (PGx) testing revolves around the clinical delivery of testing. Because multiple health professionals may play a role in the delivery of PGx testing, various clinical delivery models have begun to be studied. We propose that a partnership between genetic counselors and pharmacists can assist clinicians in the delivery of comprehensive PGx services. Based on their expert knowledge of pharmacokinetics and pharmacodynamics, pharmacists can facilitate the appropriate application of PGx test results to adjust medication use as warranted and act as a liaison to the healthcare team recommending changes in medication based on test results and patient input. Genetic counselors are well-trained in genetics as well as risk communication and counseling methodology, but have limited knowledge of pharmaceuticals. The complementary knowledge and skill set supports the partnership between genetic counselors and pharmacists to provide effective PGx testing services.

Insurance coverage policies for personalized medicine

Adoption of personalized medicine in practice has been slow, in part due to the lack of evidence of clinical benefit provided by these technologies. Coverage by insurers is a critical step in achieving widespread adoption of personalized medicine. Insurers consider a variety of factors when formulating medical coverage policies for personalized medicine, including the overall strength of evidence for a test, availability of clinical guidelines and health technology assessments by independent organizations. In this study, we reviewed coverage policies of the largest U.S. insurers for genomic (disease-related) and pharmacogenetic (PGx) tests to determine the extent that these tests were covered and the evidence basis for the coverage decisions. We identified 41 coverage policies for 49 unique testing: 22 tests for disease diagnosis, prognosis and risk and 27 PGx tests. Fifty percent (or less) of the tests reviewed were covered by insurers. Lack of evidence of clinical utility appears to be a major factor in decisions of non-coverage. The inclusion of PGx information in drug package inserts appears to be a common theme of PGx tests that are covered. This analysis highlights the variability of coverage determinations and factors considered, suggesting that the adoption of personal medicine will affected by numerous factors, but will continue to be slowed due to lack of demonstrated clinical benefit.

Pharmacogenomics in the assessment of therapeutic risks versus benefits: inside the United States Food and Drug Administration

Pharmacogenomics is the study of how genetic variations influence responses to drugs, diagnostics, or biologic agents. The field of pharmacogenomics has significant potential to enhance drug development and aid in making regulatory decisions. The United States Food and Drug Administration (FDA) has supported pharmacogenomics for nearly a decade by providing regulatory advice and reviewing applications, with the intent of discovering and applying genetic determinants of treatment effects. The FDA will continue to develop policies and processes centered on genomics and individualized therapeutics to guide rational drug development. It will also continue to inform the public of clinically relevant pharmacogenomic issues through various mechanisms of communication, such as drug labeling. In this review, we provide a perspective on several pharmacogenomic activities at the FDA. In addition, we attempt to clarify what we believe are several misperceptions regarding the FDA's pharmacogenomic initiatives. We hope this perspective provides a window into some ways in which the FDA is enabling individualized therapeutics through its mission-critical activities.

Healthcare payers: a gate or translational bridge to personalized medicine?

Healthcare payers represent stakeholders who can act as either a bridge or a gate to the translation of personalized medicine into routine clinical practice. To date, the slow realization of the promise of personalized medicine has been partly attributable to the lack of clear evidence supporting the clinical utility of genetic and genomic tests and the lag in development of clinical guidelines for the use and interpretation of tests. These factors, along with a paucity of clear guidance from healthcare payers and clinical experience with genomic tests, serve as impediments to timely and consistent reimbursement decisions. The design of alternative strategies for collaborative evidence-generation, clinical decision support and educational initiatives for healthcare providers, patients and the payers themselves are critical needs to achieve the full benefit of personalized medicine in day-to-day healthcare settings.

Survey of US public attitudes toward pharmacogenetic testing

To assess public attitudes and interest in pharmacogenetic (PGx) testing, we conducted a random-digit-dial telephone survey of US adults, achieving a response rate of 42% (n=1139). Most respondents expressed interest in PGx testing to predict mild or serious side effects (73±3.29 and 85±2.91%, respectively), guide dosing (91%) and assist with drug selection (92%). Younger individuals (aged 18-34 years) were more likely to be interested in PGx testing to predict serious side effects (vs aged 55+ years), as well as Whites, those with a college degree, and who had experienced side effects from medications. However, most respondents (78±3.14%) were not likely to have a PGx test if there was a risk that their DNA sample or test result could be shared without their permission. Given differences in interest among some groups, providers should clearly discuss the purpose of testing, alternative testing options (if available) and policies to protect patient privacy and confidentiality.

Feasibility of incorporating genomic knowledge into electronic medical records for pharmacogenomic clinical decision support

In pursuing personalized medicine, pharmacogenomic (PGx) knowledge may help guide prescribing drugs based on a person’s genotype. Here we evaluate the feasibility of incorporating PGx knowledge, combined with clinical data, to support clinical decision-making by: 1) analyzing clinically relevant knowledge contained in PGx knowledge resources; 2) evaluating the feasibility of a rule-based framework to support formal representation of clinically relevant knowledge contained in PGx knowledge resources; and, 3) evaluating the ability of an electronic medical record/electronic health record (EMR/EHR) to provide computable forms of clinical data needed for PGx clinical decision support. Findings suggest that the PharmGKB is a good source for PGx knowledge to supplement information contained in FDA approved drug labels. Furthermore, we found that with supporting knowledge (e.g. IF age <18 THEN patient is a child), sufficient clinical data exists in University of Washington’s EMR systems to support 50% of PGx knowledge contained in drug labels that could be expressed as rules.

Pharmacogenetics and pharmacogenomics of sexual dysfunction: current status, gaps and potential applications

Although treatment of different types of sexual dysfunction has improved in the past decade with the introduction of phosphodiesterase type 5 inhibitors and selective serotonin reuptake inhibitors, response rates to these targeted therapies are variable. There are a number of studies in the published literature that provide proof-of-concept that genetic variation contributes to the variable response. Pharmacogenomics will most likely be one part of our therapeutic armamentarium in the future and will provide a stronger scientific basis for optimizing drug therapy on the basis of each patient’s genetic constitution. This article will review English language medical literature on the state-of-the-art genetic polymorphisms of drug targets, transporters and signaling molecules as well as pharmacogenetic studies of sexual dysfunction and suggested possible applications. Collectively, the data demonstrate that pharmacogenomics in the field of sexual medicine is still in its infancy. More research will provide further intriguing new discoveries in years to come.

Pharmacogenomics, evidence, and the role of payers

Initial enthusiasm for the potential of pharmacogenomics (PGx) to transform medical practice has been tempered by the reality that the process of biomarker discovery, validation, and clinical qualification has been disappointingly slow, with a limited number of PGx tests entering the marketplace since the initial publication of the human genome sequence. Reasons for the delays include the complexity of the underlying science as well as clinical, economic, and organizational barriers to the effective delivery of personalized health care. Nevertheless, payers are interested in using PGx services to ensure that drug use is safer and more effective, particularly in the settings of medications that are widely used, have significant risks of serious adverse events, have poor or highly variable drug response, or are very expensive. However, public and private payers have specific evidence requirements for new health care technologies that must be met prior to obtaining favorable coverage and reimbursement status. These evaluation criteria are frequently more rigorous than the current level of evidence required for regulatory approval of new PGx tests or PGx-related drug labeling. To support payer decision-making, researchers will need to measure the impact of PGx testing on clinical and economic outcomes and demonstrate the net benefit of PGx testing as compared to usual care. By linking payer information needs with the current PGx research agenda, there is the opportunity to develop the data required for informed decision-making. This strategy will increase the likelihood that PGx services will be both reimbursed and used appropriately in clinical practice.

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.

Ethnic differences in the VKORC1 gene polymorphism and an association with warfarin dosage requirements in cardiovascular surgery patients

OBJECTIVES

Vitamin K epoxide reductase (VKORC1) is the drug target for inhibition by coumarin-based anticoagulant drugs such as warfarin. Warfarin therapy has been reported as a leading cause of drug-related hospitalization and there is therefore an urgent need to develop tests for better warfarin prescription. We report here the distribution of the intron 1 -136 T>C (1173 T>C intron) polymorphism of VKORC1, previously reported to be associated with warfarin maintenance dose in Caucasians and Japanese, in several ethnic populations from Japan and Israel, and describe its significance for warfarin dosage in Japanese cardiovascular surgery patients.

METHODS

Subjects consisted of 132 Japanese individuals and 341 Israeli individuals from four Jewish ethnic groups (86 Ashkenazi Jews, 95 Yemenite Jews, 73 Moroccan Jews and 87 Libyan Jews). In addition, 31 Japanese patients receiving warfarin therapy after cardiovascular surgery, maintained with a target International Normalized Ratio, were studied. The genotyping for the 1173 T>C intron polymorphism of VKORC1 was determined using rapid real-time PCR.

RESULTS

The allele frequency of the combined VKORC1 1173 CT and CC genotypes varied among the four Israeli ethnic groups and was, on average, much higher in the Israeli (0.728) than in the Japanese population (0.152). For the Japanese cardiovascular surgery patients, the maintenance dose of warfarin was significantly larger in the combined VKORC1 1173 TC and CC genotype group than in the 1173 TT genotype group (3.6 +/- 0.5 mg vs 2.8 +/- 0.7 mg, respectively; p = 0.02).

CONCLUSION

The frequencies of the intron 1 VKORC1 1173 T>C SNP show significant differences between ethnic groups and are associated with warfarin dose requirements for achieving a recommended International Normalized Ratio range in Japanese cardiovascular surgery patients. This study supports the example of warfarin as an appropriate model for applying personalized medicine for anticoagulant drugs, and highlights the importance of ethnicity in pharmacogenetics.

Molecular imaging and personalized medicine: an uncertain future

The Food and Drug Administration has described their view of the role that imaging will play in the approval, and perhaps postapproval, use of new therapeutic drugs. The therapeutic drug industry and regulatory authorities have turned to imaging to help them achieve better efficiency and efficacy. We must extend this initiative by demonstrating that molecular imaging can also improve the efficiency and efficacy of routine treatment with these same drugs. The role of molecular imaging in personalized medicine, using targeted drugs in oncology, is very attractive because of the regional information that it provides (in many cases, with a functional or dynamic component), which cannot be provided by in vitro methods ("regional proteomics"). There is great potential for molecular imaging to play a major role in selecting appropriate patients and providing early proof of response, which is critical to addressing the conflict between the high price of treatment and limited reimbursement budgets. This is a new venture in both molecular imaging and targeted drugs. However, there are various regulatory, financial, and practical barriers that must be overcome to achieve this aim, in addition to the normal scientific challenges of drug discovery. There is an urgent need to reduce the cost (i.e., time and money) of developing imaging agents for routine clinical use. The mismatch between the current regulations and personalized medicine includes molecular imaging and requires the engagement of the regulatory authorities to correct. Therapeutic companies must be engaged early in the development of new targeted drugs and molecular imaging agents to improve the fit between the two drug types. Clinical trials must be performed to generate data that not only shows the efficacy of imaging plus therapy in a medical sense, but also in a financial sense. Molecular imaging must be accepted as not just good science but also as central to routine patient management in the personalized medicine of the future.

Legal pressures and incentives for personalized medicine

Legal liability has the potential to be a powerful driver pushing implementation of personalized medicine. Individuals injured by adverse drug effects are increasingly likely to bring lawsuits alleging that they have a polymorphism or biomarker conferring susceptibility to the drug that should have been identified and used to alter their drug treatment. Likely targets of such lawsuits include drug manufacturers, third party payors, physicians and pharmacists, of which physicians are most at risk of substantial liability.

Common laboratory methods in pharmacogenomics studies

PURPOSE

Common laboratory methods used in pharmacogenomics studies are described.

SUMMARY

The reliable and accurate determination of a person's genetic makeup at a particular locus in the DNA molecule, or genotype, is fundamental to pharmacogenomics. Whole blood cells and buccal cells are commonly collected to obtain a DNA sample. Once DNA is collected, the genomic DNA must be isolated from other cellular material. Next, a specific region of interest must be identified and amplified, performed via polymerase chain reaction (PCR). Gel electrophoresis is often performed after PCR to verify that PCR was successful and that the amplified target sequence is the correct size. Numerous methods are available to determine a person's genotype and differ based on allele discrimination and detection. PCR coupled with restriction fragment length polymorphism (RFLP) analysis, a conventional genotyping method, does not rely on automated technology and is practical for laboratories that genotype a limited number of samples. Pyrosequencing is an automated genotyping method in which the principal allele discrimination method is a primer extension reaction coupled with a luciferase-based enzyme reaction. TaqMan relies on the use of fluorescencelabeled probes, in addition to PCR primers, in the reaction mixture, enabling PCR amplification and allele discrimination in the same step. Mass spectrometry differentiates DNA molecules using a defined mass. Denaturing high-performance liquid chromatography (DHPLC) uses a reverse-phase ion-pair column to discriminate between variant and nonvariant alleles.

CONCLUSION

An understanding of the common genotyping methods used in pharmacogenomics studies, including PCR-RFLP analysis, pyrosequencing, TaqMan, mass spectrometry, and DHPLC, will aid pharmacy practitioners and students when interpreting the methods sections of such studies.

Pharmacogenomics and the future of drug therapy

With the completion of the human genome project, many investigators are striving to translate the resulting wealth of new information into new and improved clinical practices. Pharmacogenomics represents one of the most promising of these applications for adult- and pediatric-based therapies. This article provides a historical perspective, but most importantly, uses this background to illustrate important principles of the field. The application of pharmacogenomics to asthma therapy is presented as an example of the current status of pharmacogenomics as it is being applied to an important pediatric health problem. Finally, a discussion of future promises and challenges to the application of pharmacogenomics is presented, including economic and ethical issues.

Pharmacogenetics of chronic cardiovascular drugs: applications and implications

Cardiovascular disease continues to be a tremendous worldwide problem, and drug therapy is a major modality to attenuate its burden. At present, conditions such as hypertension, dyslipidaemia and heart failure are pharmacologically managed with an empirical trial-and-error approach. However, it has been suggested that this approach fails to adequately address the therapeutic needs of many patients, and pharmacogenetics has been offered as a tool to enhance patient-specific drug therapy. This review outlines pharmacogenetic studies of common cardiovascular drugs, such as diuretics, beta-blockers, angiotensin-converting enzyme inhibitors, angiotensin receptor blockers, statins and warfarin, ultimately highlighting considerations for future research and practice.

Diagnostics and biomarker development: priming the pipeline

The decrease in the rate at which novel medical products are reaching the market, despite major scientific achievements and investment that might have predicted otherwise, is causing much concern. Although this 'pipeline problem' has often been discussed in the context of drug development, it is also crucial to examine the unique characteristics of the pipeline for biomarkers and diagnostics. Here, we characterize the pipeline problem for biomarkers and diagnostics, and consider what steps could be taken to solve it.

Managed Care Pharmacist - Pharmacogenomics and Its Potential Uses in Managed Care Pharmacy

Managed care pharmacists are involved formally with the interface between the delivery and financing of health care; their work thus entails an accountability for both elements. Interpreted broadly, managed care pharmacists are pharmacists working within the sphere of a health care system, health care purchaser, health insurer, managed care organization, or benefit administration agency. Patients, the pharmacy profession, and society are best served by this broad interpretation, because the interdependency of financing and delivery is inextricably linked to the achievement of good health outcomes. This continuing feature will explore contemporary issues facing managed care pharmacists.

Challenges and opportunities of pharmacogenetics in drug development

Drugs fail the regulatory process for a variety of reasons, including issues with pharmacokinetics, safety and efficacy. One of the most exciting questions in drug development today is how far the science of pharmacogenetics, the study of the genetics of drug response, can be used to address the fundamental issues that the pharmaceutical industry is facing. In particular, the question of how far it is possible to use this emerging science to deliver the right treatment, to the right patient, at the right dose, at the right time is both the challenge and opportunity of using pharmacogenetics in drug development. This review will address these questions with several real-life examples.

Discordance between availability of pharmacogenetics studies and pharmacogenetics-based prescribing information for the top 200 drugs

BACKGROUND

Despite growing numbers of pharmacogenetics studies, little pharmacogenetics-based prescribing information is available to practitioners. It is possible that the lack of prescribing data for commonly used drugs is due to a paucity of evidence-based pharmacogenetics literature for these agents.

OBJECTIVE

To investigate the relationship between pharmacogenetics prescribing data in drug package inserts (PIs) and pharmacogenetics research literature for agents represented in the top 200 prescribed drugs for 2003.

METHODS

A PubMed search (to August 7, 2004) was performed to identify pharmacogenetics studies relevant to the top 200 drugs. These data were compared with PIs for drugs in the top 200 list that contained pharmacogenetics prescribing information.

RESULTS

Pharmacogenetics data in the literature were available for 71.3% of the top 200 drugs. The gene involved coded for a drug-metabolizing enzyme in 34.5% of the literature sampled. The remaining 65.5% of the pharmacogenetics studies contained information largely related to genetic variability in target proteins and drug transporters. Three drugs with PIs containing pharmacogenetics prescribing information deemed to be useful to guide therapy were in the top 200 list (celecoxib, fluoxetine, pantoprazole). There was no consensus on the strength of association between genetic variability and drug response for these agents.

CONCLUSIONS

The lack of specific pharmacogenetics-based prescribing information in PIs for commonly used drugs does not seem to be related to a paucity of pharmacogenetics data in the research literature. Rather, other factors including, but not limited to, the uncertain clinical relevance of genetic associations may make practical prescribing recommendations difficult.

[Implications of pharmacogenetics in every-day practice]

Pharmacogenetics as one of the areas of clinical pharmacology addresses hereditary factors involved in individually different responses to drugs. Clinical trials combined with molecular genetics seek for underlying reasons influencing efficacy and toxicity of drugs. The declared goal of pharmacogenetics is to provide physicians with knowledge and tools to allow an individualized patient-directed pharmacotherapy. This concept is best evolved for clinical practice in the field of drug-metabolizing enzymes, especially for the cytochromes P450 (CYP) 2D6, CYP2C19 and thiopurine S-methyltransferase (TPMT). Patients with inherited enzyme deficiencies are at risk to accumulate excessive drug concentrations when treated with standard doses which may lead to adverse drug reactions or even to life-threatening conditions. Genetic factors are also involved in drug-target interactions (e. g. receptors). Prospective controlled clinical trials are needed to evaluate the benefit of pharmacogenetics for therapy outcome and to define its role in clinical practice.

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.

Novel technology and the development of pharmacogenetics within the pharmaceutical industry

This article focuses on the role of pharmacogenetics (PGx) technology across the drug development pipeline. Recent technology developments in three main areas are discussed: the discovery of polymorphisms or other variants in genes of interest; genotyping technologies used in PGx research (both for candidate gene analyses and for a whole-genome association approach); and the use of genotyping in patients prior to prescription (diagnostics). Finally, the associated issues of genetic data management and analysis are addressed, and the challenges facing the pharmaceutical industry in storing, manipulating and exploiting the large and complex data sets that will be generated from emerging PGx platforms are discussed. In conclusion, it is demonstrated that, despite the failures of some technology development programs and the slow rate of progress of others, there has, in fact, been steady progress toward the implementation of PGx within the pharmaceutical industry.

HMG-CoA reductase inhibitor pharmacogenomics: overview and implications for practice

HMG-CoA reductase inhibitors (statins) are widely prescribed and recommended as first-line therapy for most patients with hypercholesterolemia or established coronary heart disease. However, there is interpatient variability in lipid-lowering response to statins that is not explained by initial cholesterol levels and inadequate dosing alone. Genetic polymorphisms may contribute. This review discusses the potential contribution of polymorphisms in genes encoding proteins involved in drug metabolism and transport, cholesterol biosynthesis, lipid metabolism and others to lipid responses to statins.