Swiss drugmaker Novartis' cancer-fighting drug Gleevec can still help treat chronic myeloid leukemia even after five years of use, a new study showed on Wednesday.
The long-term study found that 89 percent of more than 500 volunteers who started taking the drug -- also known by the generic name imatinib -- for chronic myeloid leukemia (CML) beginning around June 2000 remained alive.
That survival rate includes all causes of death, according to the study published in The New England Journal of Medicine.
"If you look at CML-specific deaths, the rate is five%," said Brian Druker of the Oregon Health & Science University, who led the study.
"That's truly extraordinary when you think back five years ago when survival rates were less than 50 percent for this disease and we told patients they were lucky if they made it five years. Now we're saying it's more like 95% they will be alive at five years."
The researchers also found very few patients -- just 17% -- developed resistance to the drug over the five-year span.
The other remarkable feature is the risk of relapse is decreasing over time," Druker told Reuters. "That means to me that long-term survival is very likely."
The drug was the first anti-cancer medicine to be designed based on precise knowledge of how a particular cancer grows. It works by blocking a protein known as tyrosine kinase.
But it isn't effective in all cases, and other companies as as well as Novartis have been developing alternatives.
CML is relatively rare. In the United States, it strikes about 4,600 people a year.
The drug has also been approved for other rare forms of leukemia.
In October, Novartis warned Gleevec could, in rare instances, damage the heart. But in the long-term study, drug-related congestive heart failure was seen in only one patient.
The drug has been on the market since 2001.