Data confirm Dasatinib's effectiveness in resistant chronic myelogenous leukemia

Updated clinical trial results show that the drug dasatinib (Sprycel) continues to be highly effective in patients with chronic myelogenous leukemia who were unable to tolerate Gleevec or who developed resistance to it, reports a team led by researchers at Dana-Farber Cancer Institute.

Richard Stone, MD, of Dana-Farber, will present the results of the START-C trial at the annual meeting of the American Society of Hematology on Tuesday, Dec. 11, in Atlanta.

“Previous results showed that about 65 percent of patients who couldn't tolerate Gleevec or became resistant will benefit from dasatinib,” said Stone. “Now, with a longer followup of at least two years, these responses are durable. Very few people have relapsed on the drug.”

Dasatinib, an oral tyrosine kinase inhibitor made by Bristol-Myers Squibb that blocks the abnormal BCR-ABL growth signals of the Philadelphia chromosome, was approved by the Food and Drug Administration in 2006. It is 325 times more powerful than Gleevec in blocking BCR-ABL, and also inhibits other cancerous growth signals.

The international study team reported that progression-free survival 15 months after beginning treatment was 90 percent, and overall survival was 96 percent. Doses of dasatinib were interrupted at times for 87 percent of patients and doses were reduced in 73 percent because of side effects, which included lowered blood cell counts and pleural effusions (excess fluid in the chest cavity.) “These are manageable problems,” said Stone.

Because of its superior potency to Gleevec, investigators are testing dasatinib as an alternative first-line treatment. Stone said that a large Phase III trial of the drug used as initial treatment is under way at Dana-Farber and other research centers.