From today’s New York Times, another great example of ‘personalized medicine’ based on DNA testing.
The standard treatment for infection with the hepatitis C virus is a grueling 48-week course of the antiviral drugs interferon and ribavirin that gives some patients flulike symptoms and severe depression. The treatment varies in its effectiveness, being much more successful in Americans of European descent than in African-Americans.
Hepatitis C & DNA
A Duke University team has now uncovered the principal reason for the disparity between the races. It lies not in differing compliance to the treatment or access to health care, as some have assumed, but in genetics.
Using a genetic test called a genome-wide association study, the Duke team, led by David B. Goldstein and John McHutchison, found that the coding at a single site on the DNA, out of the three billion sites in the human genome, made all the difference in people’s response to the treatment.
The site is close to the gene for a special kind of interferon, known as interferon-lambda-3, and may help control the gene’s activity. Some people have the DNA unit T at this site, and others have C. Since a person inherits two copies of the genome, one from each parent, individuals may have T’s on both copies, C’s on both, or one T and one C.
People with the CC version, or allele, respond much better to the standard hepatitis treatment than do those with the TT allele. The C versions are more common in Europeans than in Africans, and this explains half of the difference in the response between the two races, the Duke team said in a report released Sunday on the Web site of the journal Nature……
People who have a lower chance of benefiting from the grueling treatment because they have the TT allele might decide to wait until better drugs become available, especially if their liver damage is not severe. On the other hand, African-Americans with the CC allele might be more confident in accepting the treatment, Dr. McHutchison said.
The science of pharmacogenetics continues to turn out new examples that medicine is not necessarily ‘one size fits all’. From anticoagulants to antidepressants, we’re really only just getting started with finding the link between the effectiveness of medicines and your DNA.
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