Personalized Medicine: Pharmacogenomics 101

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Pharmacogenomics, the study of how genes affect the way medicines work in your body, is helping advance personalized medicine and allowing healthcare providers nationwide to match individual biology to medical care.

It’s becoming more common for doctors to test for gene variants before prescribing certain drugs. For example, children with leukemia might get the TPMT gene test to help doctors choose the right dosage of medicine to prevent toxic side effects. Some HIV-infected patients are severely allergic to treatment drugs, and genetic tests can help identify who can safely take the medicines.

“If doctors know your genes, they can predict drug response and incorporate this information into the medical decisions they make,” says Dr. Rochelle Long, a pharmacogenomics expert at NIH.  “By screening to know who shouldn’t get certain drugs, we can prevent life-threatening side effects.”

Pharmacogenomics is also being used for cancer treatment. Some breast cancer drugs only work in women with particular genetic variations. If testing shows patients with advanced melanoma (skin cancer) have certain variants, 2 new approved drugs can treat them.

NIH-funded researchers recently identified a set of genes with unique activity patterns that can help assess whether someone will benefit from taking aspirin for heart health. Scientists are now working to develop a standardized test for use in daily practice. If doctors can tell that aspirin won’t work in certain patients, they can try different treatments.

One NIH-funded research team studied a different clot-fighting drug known as clopidogrel (Plavix). Led by Dr. Alan Shuldiner at the University of Maryland School of Medicine, the team examined people in an Amish community. Isolated communities like this have less genetic diversity than the general population, which can make it easier to study the effects of genes. But as in the general population, some Amish people have risk factors, such as eating a high-fat diet, that raise their risk for heart disease.

Many of the Amish people studied had a particular gene variant that made them less responsive to clopidogrel, the scientists found. Further research revealed that up to one-third of the general population may have similar variations in this gene, meaning they too probably need a different medicine to reduce heart disease risks.

The findings prompted the U.S. Food and Drug Administration (FDA) to change the label for this common drug to alert doctors that it may not be appropriate for patients who have certain gene variations. Two alternative drugs have since been developed. “If people have these gene variants, they know they have options,” says Shuldiner. “This is a great example of how study results made it onto a drug label and are beginning to be implemented into patient care.”