Definitions

personalized-medicine

Personalized medicine

Personalized medicine is the concept that information about an patient's genotype or gene expression profile could be used to tailor medical care to an individual's needs. Such information could be used to help stratify disease status, select between different medications and/or tailor their dosage, provide a specific therapy for an individual's disease, or initiate a preventative measure that is particularly suited to that patient at the time of administration. Several examples of approaches to personalized medicine have been established in medical practice, but in general the genotype-centered approach is not yet in widespread use clinically. It is currently debated whether such "personalized medicine" offers significant advantages over traditional clinical approaches that combine an individual's personal medical history, family history, and data from imaging, laboratory, and other tests.

Traditional approaches of clinical medicine

Traditional clinical diagnosis and management focuses on the individual patient's clincal signs and symptoms, medical and family history, and data from laboratory and imaging evaluation to diagnose and treat illnesses. Recent advances in medical genetics and human genetics have enabled a more detailed understanding of the impact of genetics in disease. Large collaborative research projects (for example, the Human genome project) have laid the groundwork for the understanding of the roles of genes in normal human development and physiology, revealed single nucleotide polymorphisms (SNPs) that account for some of the genetic variability between individuals, and made possible the use of genome-wide association studies to examine genetic variation and risk for many common diseases.

Historically, the pharmaceutical industry has developed medications based on empiric observations and more recently, known disease mechanisms. For example, antibiotics were based on the observation that microbes produce substances that inhibit other species. Agents that lower blood pressure have typically been designed to act on certain pathways invoved in hypertension (such as renal salt and water absorption, vascular contractility, and cardiac output). Medications for high cholesterol target the absorption, metabolism, and generation of cholesterol. Treatments for diabetes are aimed at improving insulin release from the pancreas and sensitivity of the muscle and fat tissues to insulin action. Thus, medications are developed based on mechanisms of disease that have been extensively studied over the past century. Recent advancements in the genetic etiologies of common diseases will likely improve pharmaceutical development. Thus, "personalized medicine" is in many ways simply an extension of traditional clinical medicine taking advantage of the cutting edge of genetics research.

Despite the great advancements in medicine, there remain a number of concerns:

  • Adverse effects attributed to medications.
  • Costs of developing new therapeutic agents (an average of $1 billion and 12 to 15 years to develop a new therapeutic and further $1 billion to successfully market a new product [REFERENCE NEEDED]). The failure rate of product development is very high and in many cases failure is not evident until a great proportion of this investment has been committed to large scale clinical trials.[REFERENCE NEEDED]
  • Recent slow-down in the generation of novel therapeutic agents.[REFERENCE NEEDED]

Potential applications of personalized medicine

Personalized medicine aims to identify individuals at risk for common diseases such as cancer, heart disease, and diabetes. The simple family history has long been used by physicians to identify individuals at increased risk and to advise preventive measures such as lifestyle modifications (changes in diet, cessation of toxic habits, increased exercise) earlier screening, or even prophylactic medications or surgery. Scientific advancements offer the potential to define an individual's risk based on their genetic make-up. Fields of biomedical research termed "-omics" (genomics, proteomics, and metabolomics) study the contribution of genes, proteins, and metabolic pathways to human physiology and variations of these pathways that can lead to disease susceptibility. It is hoped that these fields will enable new approaches to diagnosis, drug development, and individualized therapy.

Pharmacogenetics

Pharmacogenetics (also termed pharmacogenomics) is the field of study that examines the impact of genetic variation on the response to medications. This approach is aimed at tailoring drug therapy at a dosage that is most appropriate for an individual patient, with the potential benefits of increasing the efficacy and safety of medications. Gene-centered research may also speed the devlopment of novel therapeutics.

Examples of pharmacogenetics include:

  • Genotyping for SNPs in genes involved in the action and metabolism of warfarin (coumadin). This medication is used clinically as an anticoagulant but requires periodic monitoring and is associated with adverse outcomes. Recently, genetic variants in the gene encoding Cytochrome P450 enzyme CYP2C9, which metabolizes warfarin, and the Vitamin K epoxide reductase gene (VKORC1), a target of coumarins, have led to commercially-available testing that enables more accurate dosing based on algorithms that take into account the age, gender, weight, and genotype of an individual.
  • Genotyping variants in genes encoding Cytochrome P450 enzymes (CYP2D6, CYP2C19, and CYP2C9), which metabolize neuroleptic medications, to improve drug response and reduce side-effects.

Cancer management

Oncology is a field of medicine with a long history of classifying tumor stages and subtypes based on anatomic and pathologic findings. This approach includes histological examination of tumor specimens from individual patients (such as HER2/NEU in breast cancer) to look for markers associated with prognosis and likely treatment responses. Thus, "personalized medicine" was in practice long before the term was coined. New molecular testing methods have enabled an extension of this approach to include testing for global gene expression profiles and/or somatic mutations in cancer cells from patients in order to better define the prognosis in these patients and to suggest treatment options that are most likely to succeed.

Cancer genetics is a specialized field of medical genetics that is concerned with hereditary cancer risk. Currently, there are a small number of cancer predisposition syndromes in which an allele segregates in an autosomal dominant fashion, leading to significantly elevated risk for certain cancers. It is estimated that familial cancer accounts for about 5-10% of all cancers.[REFERENCE NEEDED] However, other genetic variants with more subtle effects on individual cancer risk may enable more precise cancer risk assessment in individuals without a strong family history.

Examples of personalized cancer management include:

  • Testing for disease-causing mutations in the BRCA1 and BRCA2 genes, which are implicated in familial breast and ovarian cancer syndromes. Discovery of a disease-causing mutation in a family can inform "at-risk" individuals as to whether they are at higher risk for cancer and may prompt individualized prophylactic therapy including mastectomy and removal of the ovaries. This testing involves complicated personal decisions and is undertaken in the context of detailed genetic counseling.[REFERENCE NEEDED]
  • Minimal residual disease (MRD) tests are used to to quantify residual cancer, enabling detection of tumor markers before physical signs and symptoms return. This assists physicians in making clinical decisions sooner than previously possible.[REFERENCE NEEDED]
  • Targeted therapy is the use of medications designed to target aberrant molecular pathways in a subset of patients with a given cancer type. For example, Herceptin is used in the treatment of women with breast cancer in which HER2 is overexpressed. Tyrosine kinase inhibitors such as Gleevec have been developed to treat chronic myeloid leukemia (CML), in which the BCR-ABL fusion gene (the product of a reciprocal translocation between chromosome 9 and chromosome 22) is present in >95% of cases. These medications specifically inhibit the Ableson tyrosine kinase (ABL) and are thus a prime example of "rational drug design" based on knowledge of disease pathophysiology.

Preventive treatment

Concerns regarding personalized medicine

Correlation with epidemiology and evidence-based medicine

This section is in progress. It will discuss the advancements that have already been made in epidemiology and evidence-based medicine. It will include a discussion of the relevance of individual predictive genetic tests taken in the context of large population studies.

Social justice and deployment of personalized medicine

This section is in progress. It will discuss concerns that advancements based on publicly-funded research may result in tests that are available only to a subset of the population. The social justice issue relates to integration of "personalized medicine" into preventive medicine on a large scale and not just for those that can afford to pay out of pocket for it.

Genetics discrimination

One of the significant barriers to genetic testing is thought to be the fear of discrimination. Discrimination from an insurer or even worse an employer. This fear has been indicated in several polls, including the Harris Poll in 2002. For the last decade there has been some form of legislation which had been mired in the House of Representatives in the United States. The current bill is called the Genetic Information Nondiscrimination Act. The bill has now been signed by President Bush. This legislation will break down a significant barrier to this technology.

Response of stakeholders to personalized medicine

There are several stakeholders: the industry, the regulators, the patients and the general public.

Pharmaceutical industry

The technologies underpinning personalized medicine could enable the pharmaceutical industry to develop a more efficient drug development process, based on the latest research on disease pathophysiology and genetic risk factors. Furthermore, a therapeutic agent could be marketed on the basis of a companion theranostic test result.

Diagnostics industry

The traditional diagnostics industry is mature and only achieving a growth rate of the order of 4% per annum.[REFERENCE NEEDED] Its products are very cost sensitive and have a relatively short life cycle.[REFERENCE NEEDED] The diagnostics industry has not been as successful as the pharmaceutical industry in attracting investment funding.[REFERENCE NEEDED] However, the advent of molecular diagnostic tests, or theranostics, opens new opportunities in a small but believed to be rapidly growing niche market.[REFERENCE NEEDED] New relationships are likely to develop between industry partners committed to personalized medicine embracing the approach of successful, specialised pharmaceutical firms.[REFERENCE NEEDED]

Insurers

The emergence of personalized medicine raises issues for those who pay for treatment. The cost of new diagnostic tests and individualized medications may be more expensive, but it is hoped that the predictive potential of personalized medicine could avert more costly treatments required after the onset of a disease.[REFERENCE NEEDED] Currently, less than 5% of all US private companies reimburse for genetic tests,[REFERENCE NEEDED] indicating that the current health care delivery system may not be able to deliver effective "personalized medicine".

Government agencies

The Food and Drug Administration (FDA) in the United States and their counterparts appear convinced that personalized medicine is going to make a profound impact on society and they are guiding this process. Dr. Andrew von Eschenbach, Commissioner of the FDA, is a strong proponent of personalized medicine, as evident from a briefing he gave to the Personalized Medicine Coalition. He and the FDA appear to be committed to bring new testing and treatments to market that are molecularly based. Dr. Eschenbach envisions a "molecular metamorphosis in medicine" that will improve our understanding of disease processes and lead to more effective tests and treatments based on this molecular-level knowledge. He likens the potential impact of these enhanced molecular approaches to the revolution in medicine made possible by the bacterial theory.

The Genomics and Personalized Medicine Act was introduced in the U.S. Congress to address scientific barriers, adverse market pressures, and regulatory obstacles. In addition, U.S. Secretary of Health and Human Services Mike Leavitt created a committee known as the Secretary's Advisory Committee on Genetics Health and Society (SACGHS) to study issues related to personalized medicine.

Patients

Since the aim of personalized medicine is to improve healthcare, patients will continue to benefit from advances in biomedical research and individualized treatments. Public education about the potential benefits of personalized medicine will be an important facet of its widespread acceptance.

Collaboration, infrastructure and technology : key enablers

The march toward personalized medicine is not driven, in some instances, on the basis of scientific hypothesis but through hypothesis generation sometimes starting with natural history. The key task is to find genes and gene variations that play a role in a disease. The first step is to associate the occurrence of a particular gene variant with the incidence of a particular disease or disease predisposition - an association that can vary from one individual to another depending on many factors, including environmental circumstances. The outcome is the development of biomarkers which are stable and predictive. Today's biomarker is tomorrow's theranostic.

The infrastructure necessary includes molecular information -biological specimens derived from tissue, cells, or blood provided on the basis of informed donor consent and suitably annotated. Clinical information is also necessary based on patient medical records or clinical trial data.

A very high level of collaboration involving scientists and specialists from varying disciplines is required to integrate and make sense of all this information.

The Harvard Partners Center for Genetics and Genomics was founded in 2001 with the specific goal of accelerating the realization of personalized medicine. Likewise, Duke University's Institute for Genome Sciences & Policy is an interdisciplinary effort aimed at personalizing medicine through the translation of advances in the genome sciences into clinical practice. The Personal Genome Project was announced by George Church in 2006; it will publish full genome sequences and medical records of volunteers in order to enable research into personalized medicine. The Laboratory for Personalized Molecular Medicine was founded in 2007 to identify specific mutations in genes linked to clinical outcome in patients with leukemia and lymphoma. Identifying the presence or absence of these mutations is becoming a standard of care for patients with acute myeloid leukemia. LabPMM also developments patient-specific molecular tests from patient tumor DNA samples. The ultra-sensitive tests are used by leading cancer treatment centers world-wide to monitor residual disease and treatment.

Not only is personalized medicine tailoring the right drug, for the right person, at the right time but it also includes evaluating predisposition to disease sometimes decades in advance of its threatened onset.

Personalized medicine and education

There are several universities involved in translating the burgeoning science into use. The difficulty is that medical education in all countries does not provide adequate genetic instruction.

A small number of universities are currently developing a subspecialty in medicine that is known by several names including, molecular medicine, personalized medicine, or even prospective medicine. These include, Duke University in North Carolina USA, Harvard in Cambridge USA, The Mount Sinai Hospital in New York City. A medical school is currently being constructed in Arizona USA to teach the field of personalized medicine; this is a project of Arizona State University and the not-for-profit Translational Genomics Research Institute (TGen). In addition to academia, the first personalized medicine practice in the United States was founded in 2007. Helix Health sees patients in New York City and the surrounding suburbs. The Laboratory for Personalized Molecular Medicine founded in 2007 to identify specific mutations in genes linked to clinical outcome in patients with leukemia and lymphoma, actively collaborates and assists academic centers and hospitals in the development of patient-specific molecular tests from patient tumor DNA samples. This has expanded and accelerated patient access to personalized medicine in test centers that otherwise do not have the resources to provide this care. The ultra-sensitive tests developed by LabPMM are used world-wide to monitor residual disease and treatment.

See also

References

External links

Further reading

  • Acharya et.al. (2008), Gene Expression Signatures, clinicopathological features, and individualized therapy in breast cancer, JAMA 299: 1574.
  • Potti et.al. (2006), Genomic Signatures to Guide the Use of Chemotherapeutics, Nature Medicine 12: 1294.
  • Potti et.al. (2006), A genomic strategy to refine prognosis in early-stage non-small-cell lung cancer, New England Journal of Medicine 355: 570
  • Sadee W, Dai Z. (2005), Pharmacogenetics/genomics and personalized medicine, Hum Mol Genet. 2005 October 15;14 Spec No. 2:R207-14.
  • Steven H. Y. Wong (2006), Pharmacogenomics and Proteomics: Enabling the Practice of Personalized Medicine, American Association for Clinical Chemistry, ISBN 1-59425-046-4
  • Qing Yan (2008), Pharmacogenomics in Drug Discovery and Development, Humana Press, 2008, ISBN 1588298876.
  • Willard, H.W., and Ginsburg, G.S., (eds), (2009), Genomic and Personalized Medicine, Academic Press, 2009, ISBN 0123694205.
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