ASCOIn a phase III study, imatinib mesylate (Gleevec), formerly known as
STI571, produced a 96% complete hematologic response rate and a 68% complete
cytogenetic response rate in newly diagnosed chronic myeloid leukemia (CML)
patients, Brian Druker, MD, said on behalf of the IRIS (International
Randomized Interferon vs STI-571) Study Group at the 38th Annual Meeting of the
American Society of Clinical Oncology (abstract 1).
"This study shows that with the right target and the right drug, you
can see remarkable results," Dr. Druker said at a media briefing
announcing the results. Imatinib mesylate, a specific inhibitor of the Bcr-Abl
tyrosine kinase, has previously been proved effective in CML in advanced stages
and in patients who no longer respond to interferon.
From June 2000 to January 2001, the IRIS study enrolled 1,106 patients at
177 centers in 16 countries. The patients, all within 6 months of diagnosis and
in chronic phase, were randomized to receive imatinib 400 mg/d or interferon at
a target dose of 5 MIU/m²/d plus cytarabine arabinoside (ara-C) at a dose of
20 mg/m²/d for 10 days per month.
Crossover was allowed for lack of response, loss of response, a rapidly
increasing white blood cell count, or severe intolerance of therapy. Median
follow-up was 14 months.
"We were astounded by how much better the Gleevec patients did,"
said Dr. Druker, professor of medicine, Oregon Health & Science University.
In contrast to the 96% complete hematologic response rate seen with imatinib
mesylate, the interferon patients had a rate of 67%.
The imatinib mesylate patients had an 83% major cytogenetic response rate
(68% complete), compared with only 20% for the interferon/cytarabine group (7%
In addition, 23% of patients in the interferon group could not tolerate the
therapy, compared with 0.7% of patients who were intolerant to imatinib