Pharmacogenomics -- The Key to Personalized Medicine?

Pharmacogenomics is more than just a 16-letter word; it’s a scientific field that just might hold the key to truly personalized medicine. But even though progress is being made in terms of understanding and applying this science to health care, there are some serious barriers to implementation. The clinical utility of pharmacogenomics has yet to be proven; in fact, there isn’t even a consensus on how to go about establishing this. And understandably so; with so many variables involved, it’s hard to nail down that type of criteria. For instance, what steps might need to be taken in order to differentiate between the influences of a patient’s genetic makeup as opposed to environmental factors that come into play?

But forget about the issues behind establishing clinical utility for a moment. Assuming that it can be established, the issue of cost will be sure to cause some fiery debates. First and foremost, more tests and clinical trials are needed, and these steps require funding that just isn’t there right now. But as researchers delve deeper into the potential benefits of pharmacogenomics, the likelihood of acquiring more funding becomes greater. More funding will hopefully lead to a better understanding of how to implement this science into the clinical setting to provide better care. But even then the issue of cost will still linger, as insurance companies and patients will try to figure out an affordable way to deliver this type of care.

Luckily, there are medical professionals like Dr. Howard McLeod and his colleagues out there, tirelessly working to collect answers to all of these questions. Dr. McCloud is an expert of the field of pharmacology from the University of North Carolina at Chapel Hill School of Medicine and a member of the FDA’s Committee of Clinical Pharmacology. He is also a contributing author to the recent New England Journal of Medicine article “Genomics and Drug Response,” which aims to educate physicians of all specialties on the potential of pharmacogenomics in the clinical setting. We were lucky enough to speak with Dr. McLeod last week, and some of the highlights of the discussion are below. If you’d like to hear the full conversation, check out the embedded podcast following the text.

I’d like to start by having you give our readers and listeners a quick background on your “Genomics and Drug Response” review article and maybe discuss your interest in this area.

Well it’s [an area] that’s been really emerging over the last decade…genetics is one of the contributors to drug response. And I suppose in terms of the efficacy of medicine and the adverse drug reactions that very commonly occur across all different classes of medicine. And so my co-authors from the Mayo Clinic, (Drs. Liewei Wong and Richard M. Weinshilboum) and myself were asked to put together a comprehensive review that really tried to pull together practicing physicians some of the main issues around genomics and drug response. And obviously you can’t cover everything in one article but there are some examples that practicing physicians really do need to know about genetics. It’s not just something for the future.

Would you be able to give some examples of pharmacogenomics are already being applied in the clinical setting and how that is influencing treatment decisions.

Certainly. There are two main areas that pharmacogenomics is been applied…one of them is in the area of dosing. It’s not something that’s necessarily very exciting—picking up the dose of a medicine is not especially sexy—but the concept that everyone gets the same dose is really something that we have questions [about] for decades in terms of drug interactions and aspects of organ dysfunction. It’s no surprise that you have altered metabolism or transport from a genetic polymorphism that you need a different dose of a medicine. Whether that medicine is a blood thinner like coumadin or warfarin or whether it’s an anti-cancer drug, the dosing is going to be different based on your genotype, just as it is if you have altered kidney function. The second area where genetics is being used is in terms in the response to medicine and that’s often whether or not a medicine is going to work or not. The most thorough examples are in the area of cancer where genetic variation in targets for therapy have been found and if you have a genetic variation in that target you’re very likely to benefit from the medicine. And often these medicines — the biologics, the tyrosine inhibitors—are quite expensive. The idea that you have to spend $20,000 on treatment and have no chance of benefit because of genetic variation is really something that hits all the different aspects of medicine. You don’t want someone exposed to the risk; you don’t someone wasting their money; you don’t want to waste their time in terms of tumors and chance of benefit. Cancer has been an area where there’s been a lot of activity choosing whether someone is going to benefit from an epidermal growth receptor antagonist, for example, or not based on genetic variation.

Assuming genomics become a larger factor in delivering health care — and it seems like that can certainly become the case as we learn more– physicians would need to become more educated in this area to make sure that the science is being applied appropriately. What processes or educational methods do you foresee in order for this to happen? Is it something where physicians become responsible for adding that layer of education or a situation where maybe genome consultants carve out a niche in the health care industry?

I think it will end up being all of the above. I really looked at the way radiology has been laid out as one of the examples in that most people that order a scan don’t know the physics behind the scan, may not even be good at reading the can and yet are comfortable with its application either through using decision support tools, iPhone apps or whatever else based on the experience that they’ve gained and they reach out to specialists as needed. So it could actually be reading the report or calling the radiologist and walking through the different cuts of the MRI in terms of its application. So I think we’re going to see pharmacogenetics layer out where in some cases maybe someone who has especially practiced in cancer or with blood thinners might be comfortable handling genetics without extra help. Others might reach out to their clinical pharmacists who are used to managing variability and drug response in the context of organ dysfunction and drug interactions and genetics really fits right in there. Or in some cases they’ll need special help; maybe a case where someone has multiple different genetic variants and needs to plan out a complex case of therapy. One would then refer to a specialist in that way and we see that now with other areas. Generalists who are comfortable adding statins to the control of cholesterol in patients as they age; at some point they refer them to a cardiologist or even sub-specialist within cardiology as needed. I think we’re going to see the same layering. And the education also really needs to be more focused on making sure someone knows what tools are available for interpreting and responding to the genetic information, as opposed to some of the efforts that have gone on where we’re really trying to retrain an internist to become a molecular biologist — I just don’t really see this as a useful tool.

To listen to the entire conversation, please access the audio podcast below. Other topics that Dr. McLeod covers are:

• The issue of cost as it applies to the advancement of pharmacogenetics and how he envisions insurance companies providing this type of medical coverage.
• Environmental factors vs. genetics; how to best use this scientific area to create the best possible patient outcomes.
• The reliability, speed, accuracy, and turnaround time of genome tests.
• The role of websites like 23andme.com, where consumers can get in depth genetic testing to help determine their risk of disease.

Do you believe that this area of science holds the key to better health care? Or is it a situation where much more research is necessary to determine how this area of science can play a role in the clinical decision process?

What reservations do you have about incorporating pharmacogenomics into your clinical decisions? Do you foresee a gap between physicians’ knowledge of pharmacogenomics/the state of the science and patients’ expectations of its capabilities?