June 25, 2001 Lately, scientists and physicians have been buoyed by strides in cancer research. Modern "smart" drugs are being designed to fight in a new way -- by blocking the signals that would otherwise tell cancer cells to grow uncontrollably. This month, the U.S. Food and Drug Administration speedily approved Gleevec, a therapy that has been described as a true breakthrough for its attack on chronic myelocytic leukemia and other cancers.
The latest salvo comes this week, in research conducted at the University of Rochester Medical Center, on a new leukemia drug, R115777. Results of a Phase I study for this drug will be published in the June 1 edition of Blood, an oncology journal.
Tested on 34 patients, R115777 was less toxic than traditional chemotherapy. In addition, 30 percent of the patients who took R115777 went into partial or complete remission. This result was somewhat unexpected, physicians say: Early studies of experimental drugs are designed to assess safety, toxicity, and whether the treatment works the way it was meant to work. It's unusual for physicians to also see significant improvements in patients, said Jeffrey Lancet, M.D., a hematologist at the University's James P. Wilmot Cancer Center and lead author of the Blood paper.
Developed and funded by Janssen Pharmaceutica Inc., R115777 works by using a farnesyl transferase inhibitor (Fti) as an agent to halt the cellular signals passed on by enzymes that lead to the overactive blood cell formation found in leukemia. FTI-based therapies have been used to treat solid-tumor cancers, but University of Rochester physicians came up with the idea to test it on blood cancers and proposed the study to Janssen and the National Cancer Institute.
After further testing in a larger group of people, R115777 may become a player in the new arsenal of cancer therapies. Still, Lancet remains cautious. "We're not expecting it to be a cure-all," he said. "But it offers another course of action. And the treatments for leukemia right now are far from adequate. This is a drug that fits into the idea that advances against cancer accrue in small steps. We hope that R115777 is another important step."
Adult acute leukemia presents a big challenge. Three in ten patients do not achieve complete remission; when an individual in his 60s or 70s is newly diagnosed, the chance for a five-year survival is less than 20 percent. Even in younger patients, the prognosis is poor when the disease relapses.
Traditional treatment usually involves chemotherapy, radiation and sometimes a bone marrow transplant. But R115777 is given in pill form, twice daily, and can be taken by patients who have relapsed. It does not prohibit them from receiving traditional treatment later.
The drug was tested at several dosages, from 100 to 1,200 milligrams, on 34 patients with different variations and stages of acute leukemia. The main side effect was a lowering of the patient's blood count, which increases chances of bleeding or contracting an infection. At the highest dosage, patients did experience neurological side effects, such as confusion and balance difficulties, that were severe enough to stop administering the drug at 1,200 milligrams, Lancet said. Further testing will begin at 600 milligrams per dose.
Eventually, Lancet hopes that even if R115777 cannot be used as a single treatment, it could be offered in conjunction with chemotherapy drugs or in low doses as a maintenance medication for patients in remission.
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