Four new or experimental drugs that cause only mild side effects showed far better ability in clinical trials to control advanced kidney cancer than results typically seen with older, more-toxic treatments, researchers reported here Sunday.
The early-stage studies involved Pfizer Inc.’s experimental pill SU11248, the experimental drug BAY 43-9006 developed by Bayer AG and Onyx Pharmaceuticals Inc. and Genentech Inc.’s recently launched Avastin and experimental pill Tarceva.
The trials were described at the annual scientific meeting of the American Society of Clinical Oncology.
Dr. Robert Motzer of Memorial-Sloan Cancer Center helped test SU11248 in 63 patients with kidney cancer who had failed prior “cytokine” treatments, including Interleukin 2 or interferon.
Motzer said tumors shrank in 33 percent of the patients. That compares with shrinkage typically seen in only about 10 percent of patients who take Avastin; about 5 percent of patients who take Interleukin 2 and about 2 percent of patients taking interferon.
“We saw six times better responses from SU11248 than the biggest current therapies,” said Motzer, who noted Pfizer plans to begin a 700-patient, late-stage trial this summer to confirm the kidney cancer results.
SU11248 works indirectly, blocking the receptor, or cellular doorway, used by a protein called VEGF that stimulates blood vessel growth. The pill is taken once a day.
Dr. Mark Ratain, an oncologist at the University of Chicago, described the results of his 484-patient trial of BAY 43-9006 among patients with various types of cancer given the drug for 12 weeks.
BAY 43-9006, which Bayer is developing with Onyx, blocks a series of proteins that tumor cells use for communication and also blocks the VEGF protein that help produce blood vessels which supply nutrients to tumors.
Ratain said 106 of the patients had kidney cancer that had spread to other parts of the body. Among those patients, 37 percent saw their tumors shrink by at least 25 percent within the first 12 weeks of treatment.
Moreover, 88 percent of the 37 patients had no worsening of their cancer after 24 weeks.
“Strong results”
“These are very strong results when you consider that few patients benefit from current treatments,” Ratain said. “It’s the difference between day and night.”
Dr. John Hainsworth, an oncologist at the Sarah Cannon Cancer Center in Nashville, described a Phase II trial in which Avastin and Tarceva were combined to treat 63 patients with kidney cancer that had spread. Only 58 patients remained in the trial and were evaluated.
Avastin, an injectable medicine recently approved in the United States for colon cancer, blocks the VEGF protein. Tarceva is an experimental pill that blocks a protein called epidermal growth factor that helps communicate information within cancer cells.
Hainsworth said 21 percent of the patients in his trial saw the volume of their tumors shrink by 50 percent after two months of treatment. Only 13 percent saw their cancer get worse during that period.
He said only two patients discontinued the trial because of side effects, both of which involved rashes.
“The combination of Avastin and Tarceva appears to be one of the most active and best-tolerated regimens in treatment for advanced renal cell cancer,” Hainsworth said.
He said the strong results gave hope that the combination, or other combinations of new therapies that attack specific proteins, can be used to keep kidney cancer under control.
“Maintenance therapy becomes a possibility,” Hainsworth said, noting that the safety of the newer drugs should allow patients to take them for extended periods.
By contrast, he said many patients have to abandon standard chemotherapy agents because they are so toxic.