Drugs are getting personal

June 1, 2010

As healthcare moves from a broader clinical mentality to more personalized, tailor medicine, pharmacogenomics is emerging as a best-practice therapy.

In recent years, population health has gained a foothold. Now it seems that the industry has come full circle and is focusing on the individual-specifically the individual's unique genetic attributes. As healthcare moves from a broader clinical mentality, pharmacogenomics-the scientific study of how individuals react to medications and how to prescribe optimal drug treatment-is emerging to personalize medicine and enable clinicians to target specific drugs to specific patients based on their genetic makeup.

Large-scale genetic studies in the recent past have provided data that can be used to better understand genetic contributions to drug metabolism. This information, when compared against and individual's genetic test result can help tailor drug therapy for most patients and minimize the chance of adverse drug reactions as well as determine which medication will be most effective in treating a certain condition, but only to a degree. Biological response to a medication often relates to how an individual's body breaks down and processes the active ingredients.

The potential long-term benefits of pharmacogenomics promote more effective dosing, improve the chances that a medication will be effective for a specific patient, offset the cost of more expensive services such as hospitalization, improve safety of drug therapies, reduce the cost of disease management and increase medication adherence.

According to pharmacy benefit manager Medco Health Solutions, approximately 50% of cancer drugs will be administered orally by 2013, with 85% of them relying on a genetic biomarker. Seven drugs specifically paired with genetic tests were in line for approval by the Food & Drug Administration (FDA) between the second half of 2009 and the first half of 2010.

According to the Pharmacogenomics Knowledge Base, which is funded by the National Institutes of Health (NIH) and managed by Stanford University, there are 26 well known pharmacogenomic gene-drug relationships. Likewise, there are six drugs for which the FDA requires diagnostic genetic testing and 30 for which a diagnostic test is recommended. Approximately 200 drugs have pharmacogenomic information on their labeling.

A few drugs have already become primary examples of the value of genetic testing to determine individual patient metabolism. Breast cancer drug tamoxifen can be ineffective in 7% to 10% of users because of the presence of the CYP2DC gene that reduces metabolism. In addition, the use of antidepressants also can slow the metabolism of tamoxifen.

A recent study by Medco of 896 people, who provided a blood sample or cheek swab after starting on warfarin therapy, indicates that those with high sensitivity fared better on a reduced dose. During the first six months of taking warfarin, those who underwent genetic testing were 31% less likely to be hospitalized for any reason and 29% less likely to be hospitalized for bleeding or blood clots than the group that wasn't tested. The cost of the test is estimated at $250 to $400.

HER-2 testing and the use of Herceptin (trastuzumab) illustrate another example of the application of pharmacogenomics. The medication, which specifically targets the epidermal growth factor receptor protein (HER-2/neu), is indicated for the adjuvant treatment of patients with HER-2 over-expressing metastatic breast cancer.

A new study by researchers at New York-Presbyterian Hospital and Weill Cornell Medical Center has found that about 44% of Caucasians taking statins are likely to have a particular gene variant and might not realize the statin's protective effects against colorectal cancer because of it. Researchers say this finding might help personalize the use of statins, allowing industry to offer patients a test to determine if they have the "right" gene to benefit from current statin drugs. There appear to be opportunities for a new class of statins for those who have the less-sensitive genetic profile.

"It's impossible to look at a person and figure out the right medication, the correct dose, and how long to remain on a drug, but genetic testing can provide better outcomes," says Robert Epstein, MD, chief medical officer for Medco and president of the Medco Research Institute. He estimates that more than 50 medications have been paired with genetic tests and submitted for FDA review. The use of the tests is growing by 45% per year.

Dr, Epstein would like to see formularies tailored to individuals and databases of genetic screening results available for reference by patients and their providers.