Ethnicity, genomics and personalized medicine
For well over a century, the Statue of Liberty has invited the world to “Give us your tired, your poor, your huddled masses yearning to breathe free.” Now, thanks to stunning advances in the sequencing of the human genome and patient-specific genetic research, America’s healthcare system is extending another invitation to this nation’s complex polyglot population: give us the rich diversity of your DNA.
Spawned by explosive advances in scientific knowledge about the human genome and personalized medicine, a revolution in patient care and medication management is on its way. Within a few years, pharmacogenomics will transform both the practice of pharmacy and the way medicines are prepared, prescribed and dispensed to patients for many chronic diseases. And it will allow prescribers and pharmacists to adapt medicines to the vast genetic diversity of America’s rich trove of ethnic groups and individual patients, based on those patients’ own ability to process and metabolize different drug compounds.
Researchers have found that more than half of all patients have variations in their DNA that can profoundly affect the way they react to many commonly prescribed medications. For instance, researchers have already established that “patients with a genetic variation in the gene identified as 2C19 are some three-and-a-half times more likely to have an adverse reaction” to the blood thinner Plavix (clopidogrel bisulfate), said Tasha Michaels, a clinical pharmacist with Kerr Drug who helped coordinate a six-month pharmacogenetic pilot program by Kerr in collaboration with the University of North Carolina’s Eshelman School of Pharmacy.
That study established the feasibility of a community pharmacy-based pharmacogenetic program and its acceptance by physicians and patients. The pilot — which involved a collaboration among pharmacists, physicians, Eshelman faculty and an outside genomic testing lab — demonstrated that pharmacists can screen participating patients, apply individualized genetic information from lab DNA tests to those patients at the pharmacy counter when dispensing prescriptions, adjust medications and dosages where needed in collaboration with the physician, and prevent drug mishaps or improve long-term patient outcomes.
Kerr’s Plavix pilot also demonstrated that pharmacists can perform the patient interventions required — including taking DNA samples from patients via buccal [cheek] swabs that “didn’t take that much more time” than a follow-up visit for medication therapy management would, Michaels said. “So you can easily work it into the pharmacy workflow.”
Drug labeling for more than 100 pharmaceutical therapies, including Plavix, has already been updated to include warnings of decreased response in individuals with certain genetic profiles. And in the not-too-distant future, predicts clinical pharmacist and former American Pharmacists Association officer Brad Tice, the vast majority of prescriptions dispensed will likely include specific genetic coding for each recipient.
“Pharmacogenomics is going to be as big for pharmacy as immunizations have been,” Tice told DSN Collaborative Care.
For some pharmacy practitioners, the new frontier of genomic-based medication therapy is already here. The advance units of community pharmacy, led by perennial retail health innovators like Kerr Drug and CVS Caremark, have already ventured into the fast-expanding world of genomic advances and pharmacogenetics with pilot programs or joint ventures that tailor drug therapy more effectively to individual patients, avoid some adverse drug reactions and in some cases, improve outcomes.
“The ultimate goal is to create ‘designer drugs’ matched to unique genetic profiles,” noted CVS Caremark in a report. Added Troyen Brennan, EVP and chief medical officer for CVS, “there is a growing desire by clients to tailor pharmaceutical treatment based on genetic inheritance.”
It’s what author Francis Collins calls “the revolution in personalized medicine” in his book, "The Language of Life: DNA and the Revolution of Personalized Medicine."
The dramatic gains made by scientists in gene sequencing have brought a more personalized form of drug therapy into focus. And the rapid growth of testing labs that can identify a specific patient’s genetic markers for his or her ability to metabolize or otherwise respond to specific drug compounds has brought the ability to tailor drug therapies to individual patients within reach of many community pharmacies.
“Pharmacogenetic testing is increasingly paving the way for more personalized drug management” and “should help improve drug response rates and reduce adverse events,” noted Howard McLeod, the Fred Eshelman Distinguished Professor of Pharmacogenomics and Individualized Therapy at the University of North Carolina’s Eshelman School of Pharmacy and director of the UNC Institute for Pharmacogenomics and Individualized Therapy.
Essentially, pharmacogenomics and pharmacogenetics — the two terms are often used interchangeably, even though they differ slightly in meaning — is the science of applying the fast-growing body of knowledge about the human genome to “how information in our genes influences our response to drugs,”McLeod said.
“In cancer and almost every other area of medicine, there are multiple drugs that work,” he noted. “But none of them work on more than half the patients. So when prescribers are faced with choosing what medicine to give a person, they often go with the drug they know best. And because there is often no way to know with great certainty how the drug may work on that individual, it may not be the one that will benefit the patient the most.”
Some of the variations are related to ethnicity. “There’s not that much ethnic variation for a drug like Plavix,” observed Michaels. “But there’s definitely more of a variable response for other drug classes,” based on “various enzymes” common to different racial groups that affect how they react to various molecular compounds. For instance, said Michaels, Asians tend to break down alcohol in their systems differently than other groups due to differences in their DNA.
APhA defines pharmacogenomics, or PGx, as “the use of patient-specific genetic characteristics to guide medication therapy, in order to maximize safety and efficacy, and narrow the drug choices for an individual patient.”
“Although the distinctions between PGx and pharmacogenetics are minimal, PGx generally refers to the study of the interactions among multiple genes/gene products and drug response, whereas pharmacogenetics is often used to describe the effects of a single gene,” noted the pharmacy group.
In the Journal of the American Pharmacists Association, APhA asserted that pharmacogenomics “will further enhance the community pharmacist’s ability to individualize therapy during medication processing or extensive MTM [i.e., medication therapy management].”
To that end, APhA said, “Pharmacists must take steps to assess the entire clinical picture and use pharmacogenomics where appropriate to optimize drug therapy.”
The tools to do so are increasingly within the reach of many pharmacists — and the need for their involvement in this expanding field of medicine is clear. “We know the genomic profiles already on 50% of medications, … and all new drugs are going to have it. So I really see pharmacists as being the provider,” Tice said. “There are not enough genetic counselors in the United States, and they’re going to mainly be focused on hereditary diseases, not as much on medication applications. So there’s even more of a need for pharmacists to step up in this area.”
What’s more, the APhA reported, “Pharmacogenomic testing technology has made conducting pharmacogenomics testing in community pharmacies possible. Pharmacists must arm themselves with the knowledge and skills specific to pharmacogenomics in order to fully integrate this expanding area into patient care and turn this into a great opportunity.”
Hurdles remain, however, for any pharmacy looking to apply pharmacogenetics to its practice model. “Despite many scientific discoveries and Food and Drug Administration-mandated drug labeling changes, neither pharmacists nor other healthcare providers recognize pharmacists as the pharmacogenomics expert,” APhA reported.
What’s more, noted the organization in a report in late 2012, “few primary care practitioners use the pharmacogenetic information contained in package inserts to order those pharmacogenetic tests that influence prescribing, even though we know that 1-in-4 prescription drugs dispensed is metabolized by polymorphic pathways.”
Another big challenge is the lack, thus far, of a clear and established payment standard for pharmacists who provide genetic-driven drug therapy and counseling, Tice said. “There are a lot of issues there. But just on a basic payment model, when the clinical justification can be established that we can test enough people to determine those who metabolize [a drug differently] … at some point, it becomes valuable from a prior-authorization perspective to pay a pharmacist to do the DNA test in certain criteria and provide counseling to the patient. It may be drug dependent, but you see a lot of the major plans are paying for these tests to be done. It’s growing very quickly.”
Lynn Dressler, assistant professor in the Division of Pharmaceutical Outcomes and Policy at the University of North Carolina’s Eshelman School of Pharmacy, and associate director of policy and ethics for its Institute for Pharmacogenomics, is one pharmacy researcher focused on “how pharmacogenomics will improve patient outcomes and change the standard of care in medicine,” according to UNC.
“I do think there’s information in your DNA that could be useful to your doctors and pharmacists, and to you as an individual, but it’s not the only piece of information that is helpful,” Dressler said. “Our lifestyle and environmental exposures also are contributing factors.”