In the emerging field of pharmacogenetics, scientists study genome variations and correlate them with drug treatment response.  For example, variations (also called polymorphisms) in genes encoding enzymes involved in drug metabolism have been found to affect the activation, deactivation, and toxicity of drugs used to treat cancer, heart disease, and psychiatric disorders.  Recently, scientists found that DNA sequence can also be used to predict responsiveness to current Hepatitis C treatment (a 48-week course of peginterferon-α-2b combined with ribavarin).

The sequence at a single DNA position (single nucleotide polymorphism, or SNP) on chromosome 19, close to the gene encoding the interferon-λ-3 protein, has a significant effect on a patient’s ability to clear Hepatitis C infection with treatment.  Patients with a C nucleotide at the critical position on both copies of chromosome 19 (CC genotype) are two to three times more likely to respond to treatment than those patients with the T nucleotide at the same position (TT genotype).

In the case of Hepatitis C, the mechanism by which one sequence is more therapeutic than the other is not yet understood.  However, sequence information can still assist doctors in selecting appropriate treatments: as alternative Hepatitis C treatments become available, doctors may bypass the current treatment for those patients with the TT genotype.

As DNA sequencing becomes cheaper and easier, and genome information becomes elucidated, the personalization of medicine may become a reality.

Just recently, a group of researchers at the University of Maryland School of Medicine have identified a variant of a gene that is believed to play a major role in determining why people do not respond to a popular anti-clotting medication. This gene variant, carried by as many as a third of the general population can put patients at increased risk for subsequent heart attacks, strokes and other serious cardiovascular problems. The interesting thing is, that this increased risk is not due to patients genetic predisposition for these disorders, but because it renders their medication ineffective.

Medicines that we introduce into our bodies often require one or several important mechanisms to unfold their intended effects: they may have to be actively transported into our cells, biochemically altered and thereby activated, or they may require deactivation and/or removal in order to not do more harm then good. Any of these processes may involve proteins on one level or another and, therefore, depend on genes. Thus, as we have maps that indicate the loci associated with genetic disorders (visit Tour > genome spots in DNA Interactive), we will soon have maps that tell us where to look if we wish to know our predisposition to the medications we use to cure ailments: whether they will do us any good, are totally useless or, in a worst case scenario, can even harm us.