By Ransdell Pierson
Dec 8 (Reuters) - An experimental AbbVie Inc drug for leukemia controlled or eliminated signs of the disease in more than 80 percent of patients who had failed to benefit from previous treatments, an unprecedented finding that could spur use of the medicine for other cancers, researchers said.
The AbbVie drug, ABT-199, works by blocking a protein called BCL-2 that allows cancer cells to overcome a natural mechanism called programmed cell death, in which the body kills off defective or cancerous cells.
AbbVie is developing the once-daily pill in partnership with Roche Holding AG.
The favorable data was seen in a phase I, or early-stage, trial involving 67 patients with chronic lymphocytic leukemia who had not been helped by chemotherapy or relapsed from such treatment.
The slowly progressing blood cancer, which mainly affects people age 65 and older, occurs when white blood cells build up in the blood, bone marrow and lymph nodes, causing them to enlarge. About 15,000 Americans are diagnosed with the disease each year.
Some 84 percent of patients who took ABT-199 strongly responded to the drug, with at least a 50 percent reduction in signs of the disease. And 23 percent had complete remissions, meaning all signs of the disease vanished.
"To achieve that magnitude of complete remission is extraordinarily promising and unprecedented in this particular type of leukemia, among patients with otherwise resistant disease," Dr. John Seymour, a researcher with the Peter MacCallum Cancer Centre in Melbourne, Australia, said in a telephone interview.
Seymour is scheduled to present data from his trial on Tuesday at the annual meeting of the American Society of Hematology (ASH) in New Orleans.
In the ongoing study, 72 percent of patients remain on the drug and are well at or beyond 12 months of treatment, Seymour said.
Seymour said patients with chronic lymphocytic leukemia that have failed to respond to therapy typically only live another 12 to 18 months. He said it was too early to say how patients in his trial would fare.
One patient in the trial died from a complication of treatment, called tumor lysis syndrome, in which killed cancer cells build up in the bloodstream.
But Seymour said dosages of the drug are now slowly increased during the first few weeks of treatment, a change that has markedly decreased the lysis risk.
Otherwise, he said ABT-199 was very well tolerated, with generally mild side effects such as nausea and diarrhea.
"For decades BCL-2 has been a sought-after target, but up until now no other drugs have had the potency and precision of ABT-199," Seymour said.
He said other malignancies, including cancers of the breast, prostate and lung, are also fueled by BCL-2, and that ABT-199 may therefore have promise in treating them.
"This compound has that potential, but we're still at the very early stages of testing it," Seymour said. "We're crawling, but we're looking forward to where we may be running in the future."