Tuesday, 15 May 2012

The Future of Personalized Medicine

Using DNA technologies to prevent adverse drug reactions

Recent advances in DNA technologies continue to provide us with a greater understanding of our own genome, and its effect on disease. Advances such as these are helping create the foundations for personalized medicine, a field of healthcare where treatments and medication are tailored to the individual patient by use of their genetic information. (USNews,& Duke Medicine, 2011)

Fig. 1 Groups of people can have genetic predispositions to how the react to certain drugs.
People with ADRs are represented by the red and green patient groups in the diagram.

One of the many benefits of  personalized medicine is the potential to prevent adverse drug reactions. Adverse drug reactions, or ADRs, (“unintended and harmful reactions to medicines that occur at doses regularly used for treatment” [World Health Organization, 2008]) are amongst the leading causes of death in many countries, and can cause a wide range of problems such as visual impairments, liver disorders, and muscle degeneration (World Health Organization, 2008). It has quite recently been found that certain people can have genetic predispositions to how they react to a drug (Science Daily, 2012), and as such, adverse drug reactions could be avoided if this could somehow be detected prior to the prescription of drugs. 

Fig 2. The SNP Dr, which uses saliva samples to
search for and analyze for SNPs.
The technology needed to do so has only recently started developing. The Imperial College London and its spinout company DNA Electronics have developed the prototype for a portable device which allows for the detection of certain areas of DNA that determine how we are most likely to respond to certain prescription drugs (DNA Learning Center Blog, 2009). The device is known as the ‘Single Nucleotide Polymorphism Doctor’, or ‘SNP Dr’, and works by searching for, and analyzing areas in our genome called ‘single nucleotide polymorphisms’, or ‘SNPs’ (Colin Smith, 2009.

Fig 3. An SNP, where cytosine has been replaced
with thymine on one strand of DNA,
and guanine with adesine on the other.

SNPs are variations in DNA sequences where a single nucleotide in the genome differs between individuals (Broad Institute, 2010). For example (as can be seen in figure 3), the codon GGA in one person might be altered to GAA in another, where the second guanine nucleotide in this segment of DNA would be replaced with adenine, this would result in a different amino acid being specified in the nucleic acid sequence (or quite possible no amino acid at all), and would thus create variations in the protein product (Human Genome Project Information, 2008). This variation of nucleotides must be present in at least 1% of the human population for it to be considered a SNP, otherwise it is merely a genetic defect. These variations are not abnormal, but rather create diversity with populations. They can influence a wide range of factors; from eye color (Paul Rincon, BBC, 2006) and other physical characteristics to susceptibility to certain diseases. SNPs can also determine how our bodies react to pathogens, toxins, drugs and vaccines.

The technology within the SNP Dr is based upon the fact that the responses a particular individual may have to certain medications can be predicted from the locations of certain SNPs. It can detect these SNPs very quickly on the spot, with the use of a saliva sample, and compare the results to a database of disease causing SNPs, such as the dbSNP (Single Nucleotide Polymorphism database) (Colin Smith, 2009).  This would make it a lot more economically viable to test whether a patient could have an adverse response to a drug, as a lot less time and money would be required than sending samples out to be analyzed in a laboratory (which is the current method of detecting SNPs). This would potentially allow better treatments for diseases such as HIV, for which some drugs are deemed uneconomical due to the fact that they only work for specific groups of patients (the white and green subsets of the populace depicted in figure 1).

The SNP Dr could prevent ADRs and make a lot of drugs more economically viable. Coupled with the fact that it would only require half an hour to analyze the data required to do so, as opposed to the current time period of half a day, makes it a great advancement in both the fields of genetics and personalized medicine.

Advancing Personalized Medicine: Tailoring Drugs to Fit a Patient's Genetic Predisposition (2012) Science News,
viewed 18 March 2012,

Finney, L (2008) Medicines: safety of medicines – adverse drug reactions World Health Organization,
viewed 17th March 2012,
<http://www.who.int/mediacentre/factsheets/fs293/en/index.html >.    

The Future of Medicine (2009) Cold Spring Harbor Laboratory - DNA Learning Center,
viewed 19th March 2012,

Personalized Medicine (2011) USNews and Duke Medicine,
viewed 16 March 2012,

Reece, J, Urry, L, Cain, M, Wasserman, S, Minorsky, P & Jackson, R 2011, Campbell Biology : Global Edition, 9th edition, Pearson.

Rincon, P (2006) Genetics of eye colour unlocked BBC,
viewed 17 March 2012,
< http://news.bbc.co.uk/2/hi/6195091.stm>.

Smith, C (2009) On-the-spot DNA analysis to test tolerance to prescription drugs gets closer Imperial College London,
 viewed 17th March 2012,

SNP (2010) Broad Institute,
viewed 17th March 2012,

SNP Fact Sheet (2008) Human Genome Project Information,
viewed 17 March 2012,

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