Before cancer drug imatinib mesylate, sold under the name Gleevec, a diagnosis for chronic myeloid leukemia (CML) ‘amounted to a death sentence,’ according to the U.S. National Cancer Institute.

Now, the drug could keep its patients alive for 10 years or longer, a new study published in the New England Journal of Medicine Thursday found.

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The most successful personalized medicine ever used

Data from the global study, which enrolled 1,106 participants at 177 cancer centers in more than 16 countries, showed that the once-a-day pill helped 83% of its patients extend their lives for at least a decade.

Prior to the Food and Drug Administration’s approval of the drug in 2001, less than one in three CML patients survived five years past their diagnosis, according to a news release ono the study from Oregon Health & Science University.

‘This has been the thrill of my life,’ Dr. Richard Silver, a hematologist and oncologist in New York who helped test the drug in patients, told NBC News.

According to Silver, Gleevec is the first targeted personalized medicine ever used — and the most successful.

One of the surviving patients is Bharat Shah, who told NBC News he had six months to three years to live upon his diagnosis in 2000.

After joining a clinical trial of Gleevec, Shah said he was back to normal within two months. After 17 years using the drug, the only side effect is that his eyes get a little puffy.

Gleevec also proved effective against other forms of cancer, including pediatric CML and gastrointestinal stromal tumor (GIST), the study found.

Common side effects, according to the study, included nausea, fatigue, itchy skin and muscle pain.

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