Genome Project Begins Paying Dividends to Patients
MELISSA BLOCK, host:
Continuing with health news, for years researchers have been predicting that advances in genetics will revolutionize medical practice. Now that's starting to happen. In a study released today, researchers say by studying someone's genes, they can predict how that person will respond to an important heart drug. NPR's Joe Palca has that story.
JOE PALCA reporting:
Warfarin is an extremely useful drug. Millions of people take it. It prevents blood clots, a frequent problem following heart attacks. Even though the drug has been around for more than 60 years, there's still a lot researchers would like to know about it.
Mr. ALLAN RETTIE (University of Washington, Seattle): We'd like to know primarily why there's such a huge variability in people's response to the same dose of warfarin.
PALCA: Allan Rettie is a medicinal chemist at the University of Washington in Seattle. Rettie says it's very hard to find the right dose for each patient, and the wrong dose can have serious consequences.
Mr. RETTIE: Age, sex, weight are very important determinants of the dose of the drug that you need. But, really, altogether they only explain about maybe a quarter of the variability in the response.
PALCA: So Rettie has been looking for genetic factors. A few years ago he assembled a group of some 200 patients being treated with warfarin. The first gene he looked at was responsible for breaking down warfarin once it's in the body. The particular version of that gene a person had had a small but measurable effect on how much warfarin a patient needed. But a year ago Rettie says another team of scientists made an important discovery. They found the gene that warfarin acts on to have its blood-thinning effect, a gene called VKORC1.
Mr. RETTIE: Our group latched on to the observations that came out a year ago and immediately started sequencing our warfarin patients to see if there was any genetic variability in their VKOR gene that might account for some of the variability in their response to the drug. And we found, to our surprise and, I guess, delight, that a very large amount of the variability in warfarin dosing and response was due to genetic variations in VKORC1 alone.
PALCA: Details of this finding appear in tomorrow's edition of The New England Journal of Medicine. Allan Rettie's colleague, Mark Rieder, says being able to predict the appropriate dose of warfarin is important for doctors and their patients.
Mr. MARK RIEDER (Rettie Colleague): Warfarin's a very tricky drug in terms of it has a narrow range where it's effective. If you go above that, you can have problems with bleeding. If you go below that, it's just not therapeutic.
PALCA: Right now Rieder says it can take months to find the right dose for a particular patient.
Mr. RIEDER: We hope that you could come into the clinic, you could test for these genetic differences, and then that would help to inform the physician to get you to your dose much quicker.
PALCA: It will still be a while before a genetic test will be available in the clinic. Rieder says it will be important to do a study testing patients' genes before they get warfarin instead of after, as was the case in the current study. Elizabeth Nabel expects that study will be done. Nabel is director of the National Heart, Lung and Blood Institute. She says this is the start of the new field that mixes pharmacology and genetics.
Ms. ELIZABETH NABEL (Director, National Heart, Lung and Blood Institute): And to have the ability to use pharmacogenetics to begin to predict who is going to respond, what doses are we going to need to use, how long are we going to treat really will help us tremendously individualize our treatment to the patient.
PALCA: In other words, doctors won't just look at your age, weight and blood pressure before giving you a drug. Soon they'll routinely be testing your genes, too. Joe Palca, NPR News, Washington.
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