MONTREAL — In March 2010, the US Food and Drug Administration (FDA) added a ‘black box’ warning to the drug clopidogrel, noting the link between certain genotypes and reduced drug efficacy. Despite the label change, however, only around one in every 200 physicians actually orders a genetic test when prescribing clopidogrel — an antiplatelet medicine marketed by Sanofi and Bristol-Myers Squibb as Plavix — according to data from Medco Health Solutions, a New Jersey–based pharmacy services provider.

The slow uptake of such testing is not due to some ingrained aversion to pharmacogenetic information, however. In work presented at the International Congress of Human Genetics here last month, Medco’s senior director of personalized medicine Lon Castle found that 30% of cardiologists and 41% of primary care providers agreed to free genetic testing when contacted after having prescribed clopidogrel for their patients. Physicians “are willing to do it; they’re eager to do it — they just need some more information to make themselves comfortable with it,” Castle says.

But after-the-fact testing is already one step too late, says Dan Roden, assistant vice-chancellor for personalized medicine at the Vanderbilt University Medical Center in Nashville, Tennessee. At the meeting here last month, Roden and his colleagues reported the results of a retrospective review of the records of nearly 53,000 regular users of the Vanderbilt health system. They looked at just six of the 99 drugs with FDA-sanctioned pharmacogenetic information, including clopidogrel, and showed that between 300 and 600 serious adverse drug reactions could have been avoided over the past five years had preemptive genotyping coupled to effective intervention strategies been in place.

With an eye to pharmacogenomically guided drug therapy, in September 2010 Vanderbilt launched PREDICT (short for Pharmacogenomic Resource for Enhanced Decisions in Care and Treatment), a system-wide effort to proactively link genetic information to the institution’s extensive electronic health record system and then alert physicians through a pop-up notice if a patient’s genetics predict any complications with medicines they plan to prescribe. As a first step to broader implementation, the trial is starting out with clopidogrel response in people undergoing heart catheterizations — a standard procedure performed on more than a million Americans each year so that doctors can monitor their patients’ coronary arteries for any signs of illness. To date, more than 3,000 people entering the ‘cath lab’ have also received a genetic test for DNA variants that have been linked to drug responses — information that then goes into their medical record.

(Click here to continue reading.)