Leukemia: Why Gleevec Got Approved

When officials at the FDA take just 2 1/2 months to approve a new cancer treatment, you know it's got to be some kind of breakthrough. And indeed the drug called Gleevec, which was given the go-ahead last week in record time, has produced dramatic results in patients with a rare malignancy called chronic myeloid leukemia. It's too early to say just how good Gleevec is. But the drug's success so far makes one thing clear. When designing a safe, effective treatment for a particular cancer, it pays to learn as much as possible about its underlying molecular biology.

Chronic myeloid leukemia is one of those rare cancers that occur as the result of a single genetic accident--in this case, a mutation that causes blood cells to multiply uncontrollably. Gleevec works by blocking the chemical signal responsible for that wayward growth.

So far, only the results from Gleevec's phase I or safety studies have been made public. The FDA based its decision on phase II "efficacy" data that have not yet been published. But researchers from Novartis and the Oregon Health Sciences University reported in the New England Journal of Medicine last month that 51 of 53 patients who had received the highest dose of the drug had gone into remission with only mild side effects--a little nausea, swelling and diarrhea. In seven of those cases, even the genetic abnormalities known to cause this cancer seemed to have disappeared. Doctors are testing Gleevec on an unusual stomach cancer that is triggered by similar molecular defects.

Such innovation doesn't come cheap. Treatment is likely to cost between $2,000 and $2,400 a month, probably for the rest of the patients' lives. Novartis plans to give a price break to anyone who's uninsured and makes less than $100,000 a year.

Still unknown is whether Gleevec can prolong life. Any time you rely on a single drug to treat cancer there's always the risk that the malignant cells will eventually become resistant.

--By Christine Gorman