Leukemia Drug Gleevec Continues to Amaze
Nearly 5 years after its introduction, most patients still doing well
FRIDAY, Dec. 3, 2004 (HealthDayNews) -- It was late 1997 and Doug Jensen, 71, of Canby, Ore., thought he'd developed a particularly stubborn cold. But his symptoms dragged on and "kept getting worse," he said.
Then Jensen got the devastating news: Blood tests confirmed he had chronic myelogenous leukemia (CML), a deadly blood cancer.
In 1997, average life expectancy for CML patients "was about four to six, maybe seven years," according to Dr. Brian Druker, a cancer researcher at Howard Hughes Medical Institute and the Oregon Health and Science University Cancer Institute, in nearby Portland.
Besides a bone marrow transplant, the powerful drug interferon was the only treatment available for patients such as Jensen, and it came with horrendous side effects.
By 1999, "it had gotten to the point where I couldn't even walk across the room," Jensen said. "My doctors finally said, 'Doug, this interferon is killing you faster than the leukemia -- we've got to take you off it.'"
At the same time, Jensen's doctor mentioned a clinical trial involving an experimental drug called Gleevec that was headed by Druker. With nothing to lose, Jensen enrolled.
"I was patient 13 -- 'lucky 13,' " he said. Within a year of treatment, Jensen's white blood cell count began to return to normal, and now, more than four years later, his bone marrow samples fail to show any detectable trace of the genetic abnormality that causes CML.
"I'm here because of Gleevec, there's absolutely no doubt in my mind," he said.
For the 5,000 CML patients diagnosed each year in the United States, "Doug Jensen's story is now the norm," Druker said. And he noted that, since its introduction, the drug has also proven effective in controlling relatively rare intestinal malignancies called gastrointestinal stromal tumors, affecting another 5,000 Americans annually.
Research continues into Gleevec and Gleevec-like compounds, with more than 250 related scientific papers being presented at the annual meeting of the American Society of Hematology, starting Dec. 4 in San Diego.
"Gleevec is what's considered a very targeted therapy," Druker said. "By that I mean that it was designed specifically to kill leukemia cells without harming normal cells. It precisely targets the [genetic] abnormality that drives the growth of these leukemia cells."
The fact that the drug's target is so specific means that Gleevec has only minor, easily controlled side effects -- in Jensen's case, some mild gastrointestinal upset and a slight protrusion of the eyes.
"Right now I approach CML patients with enormous optimism, because Gleevec is performing incredibly well," Druker said.
"The relapse rate on Gleevec after four years is 14 to 15 percent," he added, much lower than most cancer therapies. "Plus there are already second-generation Gleevecs entering phase II clinical trials, to help that 15 percent of patients who do relapse."
"When I sit down with a newly diagnosed CML patient I'm thinking about this as potentially a chronic disease that we'll treat like diabetes is treated with insulin -- we'll control it for long periods of time," Druker said.
But it's the wider promise of targeted therapies such as Gleevec that has Druker and other cancer researchers so excited.
"The important message to me is the incredible hope this gives to patients with CML, and also how that hope translates to perhaps doing the same thing with other cancers," Druker said. "This is really the future of all cancer therapies -- understanding what drives the growth of cancer and precisely targeting that abnormality with a safe, effective therapy."
According to Druker, Gleevec's long-term success has "validated that paradigm, and it's just a matter of all the other cancers catching up. In fact, there are many other drugs being developed that follow the same logic that the development of Gleevec did."
Jensen said he shares that enthusiasm.
"As far as I'm concerned, it's a miracle," he said. "I look back now from when I was first diagnosed -- I've gotten two new daughters-in-law, new grandkids. My wife and I just had our 48th wedding anniversary. Those are all things that I'd never have had, if it hadn't been for Gleevec."
To learn more about Gleevec, visit the U.S. Food and Drug Administration.