Mind to Market

Monday, August 20, 2007

FDA Steps into Personalized Medicine

Last week the FDA approved new labeling on the blood thinner Coumadin and its generic form, warfarin. The new labeling suggests that an individual's response to the drug is dependent upon their genetic makeup. Not only is the FDA opening the door to personalized medicine, but they are actually taking a leadership role in doing so, a role not characteristic of the agency.

Warfarin has been in use for some 50 years during which time it was evident that individual response to the drug was widely varied. Dosing requires careful monitoring of patients who could suffer life-threatening bleeding if dosages were too high and life-threatening clotting if the dosage were too low. A number of factors such as patient size, age and other medications were attributed to the variability in results but it was obvious that these factors did not explain the entire story.

A story in the WSJ (sub required) last week pointed out that studies over the past decade have identified two genes that were tied to the variance in results: CYP2C9 and VKORC1. Variants in either or both genes lead to different drug responses in individuals. Combining size, age and an individual's genotype can increase the confidence with which a doctor can prescribe a patient's dosage.

The FDA's leadership in making this move is a direct result of its Critical Path Initiative, a broad initiative undertaken by the agency to modernize biomedical sciences with the goal of improving the nation's healthcare. A cornerstone the CRI is the improvement of evaluation tools, specifically biomarkers and disease models. By taking this step the FDA is actively encouraging the use of pharmacogenomics; the use of genetic markers to predict an individual's response to a drug.

Already a number of labs have begun offering genetic tests for CYP2C9 and VKORC1 such as the Mayo Clinic and Labcorp. Osmetech announced last Friday that they are developing a warfarin assay that they plan to have available by the first half of 2008.

This is all being done without a critical clinical trial; the trial that compares a group of patients that are treated without genetic testing against a group that are treated with genetic testing. Given the fact that the health risk to patients without genetic testing is reduced by the extensive monitoring they undergo during their initial dosing, it is questionable whether the genetically tested patients will actually have a lower health risk. However, by taking some of the guess work out of the dosage process, doctors can more quickly converge on the correct dosage, reducing the time the patient must spend in an over- or underdosed state and certainly cutting down on visits to the doctor for monitoring.

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