A novel experimental agent for chronic lymphocytic leukemia (CLL) has been found to be highly active and well tolerated in patients who have relapsed and are resistant to other therapy, according to an interim study.
The agent, called PCI-32765, is the first drug designed to target Bruton’s tyrosine kinase, a protein essential for CLL-cell survival and proliferation.
CLL is the most common form of leukemia, with about 15,000 new cases annually in the U.S. About 4,400 Americans die of the disease each year.
Study co-leader Dr. Susan O’Brien of The University of Texas M.D. Anderson Cancer Centre reported the analysis, which involves 61 patients who have relapsed and whose cancer no longer responds to standard CLL therapy.
Of these patients, 27 received a drug dose of 420 milligrams (mg) and 34 received a drug dose of 840 mg.
This study found that 70 percent of patients in the 420-mg group had either a complete or partial remission to treatment after 10 months of follow-up.
“These interim findings are truly exciting because they provide additional evidence that PCI-32765 is a highly active oral therapeutic that produces a high rate of durable remissions – the remissions last months on end – with acceptable toxicity in relapsed and refractory CLL,” Dr. John C. Byrd, director of the division of hematology at Ohio State University Comprehensive Cancer Center and study’s co-leader, noted.
“These responses last for many months in part because patients are willing to remain on the drug since the side effects are very tolerable,” he said.
Complete remission means there is no detectable CLL anywhere in the body; partial remission means that the individual’s disease volume has decreased 50 percent or more in a sustained manner.
“Usually patients with highly resistant and refractory CLL would have progressed and possibly died by this time, but 82 percent remain on PCI-32765 and continue to improve,” Byrd added.
The findings were recently presented at the 53rd Annual Meeting of the American Society of Hematology in San Diego.