The drug, known as Gleevec or STI-571, is one of a new class of drugs that target cancerous cells and switch off the fundamental cancer-causing mechanism.
This form of "molecular targeting" has been shown to be effective in fighting one form of leukemia, called chronic myeloid leukemia, and a rare type of stomach tumor.
"This single drug is as interesting and impressive as any we have ever seen throughout our long war on cancer," Secretary of Health and Human Services Tommy Thompson said at a news conference this afternoon.
Clinical tests began in June 1998, but the FDA put the drug on a fast track to approval after 90 percent of patients in initial trials saw their white blood cell counts drop to normal or close to normal.
While such a short trial period leaves many questions unanswered, the maker of Gleevec, Novartis, has started mass producing the drug. At a cost of roughly $2,000 a month, Gleevec is expected to be available in pharmacies this month.
Researchers emphasized that the long-term effects of the drug are still unknown, but "early studies have shown that Gleevec will offer a significant improvement for many patients," said FDA acting Commissioner Bernard Schwetz.
Roughly 5,000 Americans are diagnosed with chronic myeloid leukemia each year. It is one of the four main types of leukemia. To date it has typically been treated with drugs such as interferon, or with potentially risky bone marrow transplants. The disease claims about 2,300 American lives every year.
Other clinical trials have shown that Gleevec is also effective in treating a form of gastrointestinal cancer. About 2,000 Americans are diagnosed with that condition annually.