Martin Champagne, MD, FRCP(C)
STI-571, also known as Gleevec, was approved for the treatment of chronic myeloid leukemia, or CML, one of the four main types of leukemia. It has also achieved remarkable clinical trial results in the treatment of a rare intestinal tumor called gastrointestinal stromal tumor, or GIST. Researchers are also beginning to look at the effects of this new drug on children with CML, and in phase I clinical trials, the drug is showing promising results. Dr. Martin Champagne, a medical oncologist at St. Justine Hospital in Montreal, Canada, is the principal researcher of the current study investigating the use of Gleevec in children with CML. Below, he discusses these promising results and the special considerations involved in testing new drug treatments on children. Q: Could you summarize the results of the trial? The levels that we achieved in the patients were at levels where we would expect to see anti-leukemic activity based on preclinical models. Q: So is it common for drugs to be tested separately for children and adults?
The trial is a phase I trial, which means that we're looking at the dose-limiting toxicities and the maximum tolerated dose in children with the Philadelphia chromosome-positive leukemia, which is the defining characteristic of this particular type of rare leukemia. We were also looking at the way that their bodies were handling the drug. We have found that the drug is fairly well tolerated in the children tested.
Yes. Children are not young adults. You can't figure out how the body will handle the drug just by making a sample rule of three and dividing by body weight. So we have to do specific studies to find out how they will handle and tolerate the drug - which is different in most studies than in adults.
Q: What kind of side effects have you seen in the study? Q: How safe is this drug in children? Q: And when will the trial be completed? Q: This drug has been tested for safety in children, but what about efficacy? Q: Do you foresee any future implications for the use of Gleevec in children with leukemia? Q: Do you believe that this drug could be a cure for leukemia in children as well as adults?
The most common toxicities that we found were minor nausea and vomiting. We also had some toxicity related to what we call the hematological parameters, which is a little bit of anemia, and decrease of white blood cells, which is no surprise in patients with leukemia at the start.
Although we did escalate the drug by different levels, and we increased the drug at a fairly high amount of total dose, we did not encounter significant toxicity of one organ or one function of the body that will prevent using the drug in children at the set dose. So, actually the drug was well tolerated for most of the kids.
The trial is still underway. We're looking for more patients so that we can test the drug at two levels, to find out if the preliminary information we got is consistent.
We have no data yet that I can comment on. But we hope at least from our preclinical model that it will work, because the Philadelphia chromosome, which is the defining feature in these types of leukemia, is not different in the pediatric patients than it is in the adults. But we have to figure that out. We just don't know yet.
There will be many challenges, because these particular types of leukemia are different in children than they are in adults. We'll ask medical oncologists to figure out what the best timing and schedule would be for giving the drug to children. We'll have to look at how we can incorporate the drug with chemotherapy trials, to see if we can build better results by using combination therapies.
I hope for some kids it will be the solution. But you have to keep in mind that these types of leukemia are rare in children. They represent only about 2 to 3 percent of the most common type of leukemia, which is the acute lymphoblastic leukemia. So the major proportion of patients will have to rely still on other therapeutics to achieve a cure.
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