Personalized Medicine Through Pharmacogenetics

THIS YEAR, 38-YEAR-OLD ACTRESS AND PHILANTHROPIST ANGELINA JOLIE HELPED RAISE AWARENESS ABOUT THE POWERFUL BENEFITS OF GENETIC TESTING. IN MAY, WHEN TEST RESULTS INDICATED THE PRESENCE OF A GENE LINKED TO BREAST CANCER, SHE CHOSE HER OWN PATH: A DOUBLE MASTECTOMY.

WHILE MOST PEOPLE UNDERSTAND HOW GENETIC TESTING CAN HELP DIAGNOSE AND TREAT DISEASES LIKE CANCER, DID YOU KNOW THAT A PERSON’S GENETICS CAN ALSO DETERMINE HOW WELL MEDICATIONS HELP MANAGE PAIN? PHARMACOGENETICS, A RELATIVELY NEW AND GROWING SUBSET OF GENETIC TESTING, CAN PROVIDE VALUABLE INFORMATION THAT CAN INCREASE THE EFFICACY OF MEDICAL TREATMENTS AND BETTER MANAGE CHRONIC PAIN.

TO EXPLAIN HOW PHARMACOGENETICS IS TRANSFORMING TREATMENT STRATEGIES FOR PEOPLE IN PAIN, PAINPATHWAYS SPOKE WITH KRISTEN REYNOLDS, PhD, VICE PRESIDENT OF LABORATORY OPERATIONS FOR PGXL LABORATORIES, THE FIRST CLIA-CERTIFIED LABORATORY TO EXCLUSIVELY OFFER CLINICAL PHARMACOGENETICS TESTING IN THE UNITED STATES, AND ANGELA HUSKEY, PharmD, CPE, ASSOCIATE VICE PRESIDENT OF CLINICAL AFFAIRS FOR MILLENNIUM LABORATORIES.

PP: What is the difference between genetics testing and pharmacogenetics?

HUSKEY: Genetics testing is an umbrella that includes a variety of tests. Pharmacogenetics is one type of testing that offers information about how your genes impact your response to medications.

REYNOLDS: Pharmacogenetics is a subset of genetics testing, but it is not testing for inherited diseases and doesn’t identify pathologic conditions. Instead, pharmacogenetics identifies medication sensitivities and is the first step in providing personalized medicine. It helps physicians identify the right medications in the right doses for each individual patient.

PP: How are patients treated?

HUSKEY: For pharmacogenetics, most testing involves the collection of saliva samples into a tube. The sample is then studied to look for variations in enzymes, and the information and test results help the physician determine the medications with the most efficacies and least toxicity for that particular patient. Most tests are complete within five to seven working days.

PP: Which patients benefit from pharmacogenetics?

REYNOLDS: I think genetic diagnostics put into clinical use will eventually become a new standard of care. In the pain management field, many of the drugs prescribed are opioids, which only work if the liver can activate them. If a patient’s liver can’t activate the medication, then the patient is basically taking a drug that will never work and continues to suffer from inadequate pain relief.

Many times, if the patient reports that medication is not working, the physician will increase the dose, and this leads to an increased potential for adverse side effects. The physician might order a urine drug screen to determine if the patient is taking the drug correctly, and this urine test can look like a false negative if the patient can’t metabolize the medication. Pharmacogenetics can identify the patients not receiving or not likely to receive benefits from the medication.

HUSKEY: Currently, pain management and treatment depends on objective pieces of information for the most part. Pharmacogenetics is useful to the clinician before prescribing medication and also when the patient is having an unexpected response to the medication. It essentially moves us beyond the current standard of care. Physicians who might have labelled patients as drug-seeking can now identify a valid, legitimate reason that medication is not working for that patient.

PP: Have you seen pharmacogenetics make a difference in patient care?

REYNOLDS: Yes. One patient, a middle-aged man, presented with chronic back pain and said the prescribed medications were not providing any relief. He had conflicting urine screens, so he had pharmacogenetics testing done, which showed he was a poor metabolizer of the medications. He wouldn’t have had normal urine screen results, but with the tests, the physician was able to switch him to a different class of medications that worked.

HUSKEY: A clinician was seeing a patient thought to be complaining and drug seeking. This patient went to a pain specialist who ordered the tests, and it was found the patient had a deficient enzyme. Another patient had done well with a particular drug for four years, but then began experiencing side effects. The test identified a drug interaction. We hear on a regular basis that pharmacogenetic testing does change the clinician’s recommendations for drug treatments.

RELATED: Genetic Mapping + Super Computing = Personalized Medicine

PP: What are the challenges and possibilities for pharmacogenetics in the future?

HUSKEY: There’s a huge need for education on pharmacogenetics, both with patients and with clinicians. It can help drive therapy, but I’m not sure most clinicians could describe the difference between pharmacogenetics and genetics testing. However, the utilization is increasing quickly along with the understanding of what to do with the results. Experience is really going to be the driver.

REYNOLDS: Pharmacogenetics testing is an important topic for any patient to discuss with his or her physician. Particularly with pain patients, establishing the pros and cons of a medication and understanding the risk of failure is imperative. But there is still a large educational gap in the medical community and we’re working to help physicians understand how pharmacogenetics can help decrease the costs associated with adverse or inadequate reactions to medications. If you drive without a seat belt, you are at increased risk of serious injury. It’s similar if you have a pharmacogenetic gene variant — that increases your risk of adverse side effects.

HUSKEY: The sky is the limit. Pharmacogenetics is one of the most rapidly progressing fields that I’ve ever been involved in; there’s been an explosion of literature published in the past decade. Not only will we continue to discover more genes, there will be a time when we will have discovered enough genes that testing will be useful for every single drug. {PP}