For many cardiac patients who receive stents–tiny tubes that help restore blood flow through clogged arteries–a gene that is responsible for processing a common anti-clotting drug can complicate their recovery.
Worldwide, there are more than 2 million stent procedures performed each year, about 528,000 in the U.S. alone. But up to 30 percent of Caucasians and up to 50 percent of Asians carry at least one copy of the gene known as CYP2C19*2, the “star-2 allele.” Carriers of that gene have a 42 percent higher risk of death, stroke, or second heart attack after stent procedures if they are given clopidogrel (Plavix), because the gene prevents the drug from working properly.
Now, Canadian biotech firm Spartan Bioscience has developed the first bedside genetic test for heart patients, the Spartan Rx. The device tests DNA from a simple swab of cheek saliva to identify star-2 allele carriers, allowing patients to be treated with the right anti-clotting medication.
The unit is the size of a toaster and nurses with no previous genetic testing experience can typically learn how to use it quickly. Results are available in 60 minutes, a huge time savings compared to standard DNA lab tests that take 2-7 days. It’s important to identify star-2 allele carriers as soon as possible, because 40-50 percent of major adverse cardiac events that occur after stent procedures happen in the first 24-48 hours.
In their proof-of-concept study called RAPID GENE, researchers from the University of Ottawa Heart Institute found that the Spartan Rx device correctly identified patients, who were then placed on the optimal drug right away. For those that were identified as star-2 allele carriers, treating them with the more potent drug prasugrel eliminated high levels of platelet markers in their blood. The study was recently reported in The Lancet.
“Essentially, for the one-third of patients who were at risk using standard therapy, with this point-of-care genetic test, we are able to eliminate that risk altogether,” says Derek So, MD, FRCPC, MSc, an interventional cardiologist at the University of Ottawa Heart Institute in Ottawa, Ontario.
For patients who are not star 2 allele carriers however, standard clopidogrel therapy is still a good choice. It has been one of the most commonly prescribed drugs in cardiology for the last 10 years, has a well-established history, and has less risk of bleeding than the more potent anti-clotting drug prasugrel. Targeting the right drug for the right patients will also have a positive impact on healthcare costs. Clopidogrel costs less in countries where the Plavix patent has expired, as it has in Canada and the U.S., and the cost of prasugrel (Effient) is similar to the cost of Plavix.
Interestingly, this is the first foray by Spartan Bioscience into the medical field. The company had already developed the technology for rapid genetic testing, but for non-medical applications such as testing for listeria during the Canadian tainted-meat crisis or testing water. Dr. So and his co-investigator, geneticist Jason Roberts, MD, collaborated with Spartan Bioscience to develop the technology for clinical application with cardiology patients.
While the Spartan Rx looks at a single, but most prevalent genetic factor that complicates treatment for stent patients, next-generation devices will attempt to process multiple genetic factors in faster time frames.
Beyond targeted treatments for stent patients, Dr. So comments that this application can be very easily adopted to other areas of medicine where genetics may be important, such as HIV drugs, or identifying which emergency room patients might benefit the most from steroid treatment. “We are at a stage where this can be done very quickly. What we need are champions in each field to quickly put their minds together,” says Dr. So.
CONNECT THE DOTS
Watch this video to hear Dr. So present results from the RAPID GENE proof-of-concept study at a medical conference last November. Learn more about stents from the National Heart Lung and Blood Institute. You may also like our earlier posts, “Family Learns Health Secrets Through Genome Sequencing” and “New Designer Drugs for Stroke Prevention in Atrial Fibrillation Patients.”