Scientists present clinical trial results for the first bedside genetic test
How quickly can clinicians accurately determine the way a patient will respond to medication, or their chances of getting a disease? It might even begin the minute they walk in the door. ‘Genotyping by eye’, as Atul Butte from Stanford University phrased it at a recent Xconomy forum, can be as instantaneous as noticing a patient is obese, a factor that increases chances of diabetes more than any known genetic variant today.
More precise genetic tests are fast catching up to this idea of near-instant genotyping as well. Researchers from the University of Ottawa recently demonstrated the success of a ‘bedside’ genetic test to optimize treatments for patients undergoing coronary stent implantations. At the Transcatheter Cardiovascular Therapeutics symposium this week, the lead investigator, Dr. Derek So, presented the results of the RAPID GENE clinical trial, a point-of-care genetic test to identify carriers of a common genetic variant that reduces the efficacy of standard anti-platelet therapies.
Patients who carry the allelic variant CYP2C19*2 respond poorly to Plavix (clopidogrel), the standard anti-platelet therapy administered after cardiac stent procedures for acute coronary syndrome or stable angina. The CYP2C19*2 variant of the cytochrome P450 2C19 gene occurs in about 40% of Asians and 25% of Caucasians, and reduces the carriers’ capacity to efficiently metabolize drugs like clopidogrel. As a result, standard medication does not provide these patients the anti-platelet protection they need.
The RAPID GENE test used to identify these patients was based on a saliva sample taken from patients and inserted into a testing machine. Within 60 minutes, nurses administering the test had results identifying which patients carried the ‘poor metabolizer’ form of the gene.
For the trial, patients were divided into two groups- the first received the standard clopidogrel therapy, while the other group was tested with the RAPID GENE test before being prescribed medication. In the second group, carriers of the CYP2C19*2 variant received an alternate medication, prasugrel (Effient). About 180 patients were tested, with approximately 50% in each group. All patients whose prescriptions were based on their genetic test results received adequate protection from their medication. In the control group however, approximately 30% of CYP2C19*2 carriers did not respond well to Plavix, demonstrating the significance of the genetic test- based therapeutic decision.
Tailoring prescriptions based on patient genetic profiles is not uncommon. Treatment for breast cancer patients has been optimized based on HER2 receptor profiles for over a decade now. More recently, sequencing an entire family’s genome enabled researchers to identify disease variants and confirm a genetic basis for the precise, physician-optimized dosages of anti-coagulants prescribed to the father, which could help his children in the future as well. Though pharmacogenetic strategies such as these are no longer just a futuristic fantasy, routine clinical genetic testing has been hindered by economics, the need for trained specialists to perform the tests, or the amount of time required for results to become available. The speed, precision and success of the RAPID GENE test illustrate the potential of point-of-care pharmacogenetic strategies to improve clinical decisions and healthcare choices in all fields of medicine.SHARE