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TwitThisTailoring Drugs for Prime Time
As pharmacogenomic knowledge advances, regulators at the Food and Drug Administration are wrestling with the type of testing they should require from drugmakers, and the information they want drug companies to provide to doctors and patients. In 2002, Strattera, a new drug for attention deficit/hyperactivity disorder, became the first drug with a message on its label informing doctors they could test patients to determine their version of the 2D6 gene.
Last year, an advisory committee to the FDA recommended that such information be added to the label for mercaptopurine. This would not only benefit leukemia patients, whose doctors are now generally aware of the genetic issue, but also patients who suffer from Crohn's disease, a much more common ailment that is often treated with a similar drug.
When Randy Adams had a flareup of Crohn's disease in 1999, it caused such crippling stomach pain that he had to go to the emergency room. Doctors put him on a powerful drug called Imuran, which keeps the body's immune system from attacking healthy tissue. But because Imuran, a cousin of mercaptopurine, can cause severe side effects, doctors use it cautiously, and Adams's doctor was no exception: He set the dose low, then stopped the drug after a couple of months when it seemed not to be working.
As luck would have it, Adams's fiancée, Melanie, had started working at a pharmaceutical firm, Prometheus Laboratories, which performs pharmacogenetic tests. Her colleagues urged Adams to consult a specialist and take a test for the TPMT gene.
The test brought good news: Adams had a version of the gene that would allow him to handle much higher doses of Imuran. His doctor increased his dose sixfold and the pain and inflammation were soon under control, without negative side effects or need for surgery. "I felt great," said Adams. "I had energy, I could run for a mile and I didn't have to have surgery."
Soon, checking patients' gene types and tailoring their dosage may be so routine that patients are unaware of the process. Early this year, a few weeks before he was going to have hip replacement surgery at Barnes- Jewish Hospital in St. Louis, Hal Regele, 64, was asked if he wanted to participate in a gene study for patients taking warfarin. He agreed, and a few days before his scheduled surgery, he learned his postoperative dosage of warfarin would be cut in half.
Regele has a variation of the 2C9 gene that makes him a poor metabolizer of the drug. His surgery went well, but when it was over and he was home on warfarin, he developed bruises and swelling and had to return to the hospital. Measurements of his blood showed it was excessively thin, despite the reductions in his warfarin dose. Doctors took him off the drug for two or three days, and then lowered his dosage again, allowing his blood to reach safe levels.
Despite the problems, Gage said the gene testing was a success. "Just imagine what could have happened to him if he had gotten a standard dose," he mused. "Instead of having some localized bruising and bleeding, he might have bled somewhere that would have been worse, possibly into his brain. As they say on Star Trek, we took evasive action. It was certainly better than it could have been."
Getting Tested
If your doctor prescribes any of the drugs mentioned in this story, discuss the need for a test. A warning: The tests run $250 to $500, and insurance may not pay.
- Genelex offers a direct-to-consumer test. You can contact their office at 800-523-3080.
- Prometheus Laboratories offers pharmacogenetic testing through a doctor. To contact, call 888-423-5227.
- Nanogen makes the genetic chip used in Mayo Clinic tests. For other testing sites, call 877-626-6436.
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