What they found, says Wartman, was that a certain gene called FLT3 was unexpectedly overproduced by his cancer cells. It so happens that a drug approved for kidney cancer inhibits that gene, and within days, Wartman started taking it. The drug sent his leukemia into remission, though he eventually had to call a halt because it also lowered his blood cell counts, a side effect. Now "I'm in uncharted waters," he says, adding that he remains in remission and is weighing the risks and benefits of taking the drug again.
Wartman points out that this is very much an emerging technology. "We've gone from a kind of Model-T Ford to a Maserati in just a few years," he says. But his case is a "very clear example" of personalized medicine's potential power, he says. He predicts that the next decade will usher in a whole new era of tailored cancer treatments.
Most will probably not be miracle cures. For many patients taking the new targeted therapies, the added benefit is measured in months; cancer cells can eventually find their way around drugs that target a specific glitch. But for others, a reprieve lasts for years. The 10-year survival rate for chronic myeloid leukemia is now above 80 percent, compared to 20 percent in the pre-Gleevec days. The hope is that different drugs could be prescribed in combination or succession and turn cancer into a chronic disease.
On other fronts, doctors are using genetic information to predict how a patient will respond to a drug. The HIV drug abacavir, for example, can cause a potentially deadly reaction in 5 to 8 percent of patients, so they get a genetic test to see if they should take the drug. Tests to gauge whether a person will get the full benefit of the anti-clotting drug Plavix, to figure out the best dose of the blood thinner warfarin, and to see who's likely to experience muscle pain or weakness on the anti-cholesterol drug simvastatin are also available.
Figuring out who will experience drug toxicity is key, because rare side effects have the potential to sharply curb the use of effective drugs. Clozapine, for example, is an antipsychotic that works but is a last-resort drug due to a dangerous side effect affecting the white blood cells, says Jeffrey Lieberman, chairman of psychiatry at the Columbia University College of Physicians and Surgeons. Researchers are now searching for genetic signatures that can predict who is at risk.
Increasingly, too, the roots of baffling diseases are being uncovered by peering deep into the genome. At the Medical College of Wisconsin and the Children's Hospital of Wisconsin, for example, researchers most famously identified a unique mutation in the DNA of young Nic Santiago Volker, who developed a crippling disease as a toddler that ravaged his digestive tract and required the removal of his colon. From 2007 until 2010, pretty much all of Nic's nutrition was delivered intravenously, recalls his mother, Amylynne Santiago Volker.
In 2009, when Nic was 4, sequencing of the 1 percent of his genome containing instructions for making proteins found a mutation linked to an immune-system disorder that doctors suspected was also responsible for his GI illness. In 2010, Nic was treated with a cord-blood transplant, a treatment for the immune disorder. A few months afterward, he was able to eat. "He got a steak first. That's what he wanted," his mother says.