Personalised Medicine
Personalised medicine
Personalised medicine is the use of an individual's genetic and genomic
information to provide the best possible healthcare for that person,
including:
Prevention
Identification of genetic risk factors for disease may mean that diseases can be diagnosed early and possibly even prevented.
Despite
major advances in recent years, research into the relationship between
genomic variation and disease risk is still in its infancy. There are
very few diseases for which the genetic contributions are simple: In
most cases, a combination of many genomic elements interact with a
host of environmental factors.
Several
common
diseases have relatively clear genetic signatures or predictors, and a
small number are controlled by a single pair of genes - the 'monogenic'
diseases. For
example, people with certain mutations in the BRCA1 gene have a higher
risk of developing breast, ovarian, and possibly prostate and colon
cancers. People with certain changes in the apoE gene have a higher
risk of developing Alzheimer's disease. However, even in these
well-studied cases, the genetic change does not tell the whole story
but is one of many contributing factors, including other genes and
environmental factors.
Since 2006 there has been an explosion
in
the studies uncovering new genetic linkages of common disease. Much
data has been generated by 'genome-wide association studies' that
correlate known single point genetic mutations (single nucleotide
polymorphisms, SNPS) with specific diseases. Although some of these
associations may prove
clinically useful, in reality many are simply too weak to make a strong
prediction. For example, a single base variation may change an
individual's lifetime risk of a disease from 2% to 4%; Although this
has doubled their risk relative to the rest of the population, it may
be hard to argue
for clinical intervention as a result.
As genome sequencing and
associated informatics technologies improve, this knowledge base will
be expanded gain a higher-resolution map of the genetic
cause of disease. Increasingly, researchers are analysing more complex
genetic variants such as Copy Number Variations (CNV) that are
associated with disease. With a clearer idea of risk profiles and how
genomic markers interact with environmental factors, disease prevention
strategies
more meaningful and potentially change healthcare management into a
truly preventative paradigm.
As well as managing patents' risk factors, highly accurate screening
programmes for early diagnosis may offer cost effective healthcare for
large populations.
Diagnosis and Treatment: Personalised medicine
Genetic analysis may enable the identification or diagnosis of a
disease or a disease sub-type, facilitating rapid and appropriate
treatment for individuals based on their own genomes.
For
example, where diseases do not appear as a well-defined set
of symptoms and signs it may be appropriate for a
genetic test to be used to diagnose the presence of a disease, an
approach that is already used in muscular dystrophy.
In some
cases it may be possible to use a patient's genotype to predict their
response to a drug treatment or protocol. In this way a patient's
treatment can be tailored for the best possible efficacy and lowest
risk of side effects. For example, warfarin is an effective
anti-clotting medicine, but difficult to manage as patients respond
differently to different dosages. Recently, studies understanding the
genetic roots of the warfarin response have resulted in new genetic
tests that allows physicians to tailor the dose to the patient,
minimising dangerous side effects and maximizing the therapeutic
efficacy of the drug.
There are already some treatments
available that are specific for an individual patient's genetic makeup.
For example the breast cancer drug trastuzumab (Herceptin), only works
in the 20% of patients whose tumour cells show high expression levels
of the HER2 gene.
Another cancer drug, Imatinib (Glivec) is used
for chronic myelogenous leukaemia. However it is most effective in
patients who have the 'Philadelphia chromosome', a genetic abnormality
created when part of chromosome 9 wrongly attaches to chromosome 22
during cell division.
Although already underway, personalised
medicine is still in its infancy. Cheaper and faster genome sequencing
technology will facilitate the development of personalised medicines in
two ways. First, a more complete understanding of the
genotype-phenotype relationship will allow researchers to identify the
biochemical pathways that are different in patients with disease,
uncovering potential new drug targets for drug development and early
markers for disease detection. Cheaper and faster sequencing will also
allow companies developing new drug treatments to more fully understand
the relationship between genotype and drug response, increasing
therapeutic efficacy and decreasing the risk of adverse events.
Cost benefits of personalised medicine
In addition to improving health outcomes, personalised medicine is
expected to deliver greater cost efficiency for healthcare providers,
as prevention, diagnosis and treatment becomes more tailored to - and
successful in - individual patients.
