The experimental drug, called PTK/ZK, is paired with what is considered the best chemotherapy combination available for advanced colorectal cancer, so study volunteers will receive the highest standard of care.
All volunteers enrolled in the studies will get chemotherapy; half will also receive PTK/ZK, while half will be given a placebo. Researchers hope that PTK/ZK will cut off the blood supply that allows tumors to grow and spread, said Dr. J. Randolph Hecht, a Jonsson Cancer Center researcher and national lead investigator for the studies.
A tumor cannot grow bigger than a pinhead unless it establishes an independent blood supply through a process called angiogenesis. Researchers theorize that by stopping or cutting off this new blood supply, they can starve and hopefully kill the cancer. PTK/ZK, an angiogenesis inhibitor, is designed to block the cellular receptors for VEGF, or vascular endothelial growth factor, which signals blood vessels to grow.
"It's a little like satellite television," Hecht said. "The signal, VEGF, is picked up by the receptor, which is like a satellite dish. If you're a blood vessel, this signal tells you to grow. What we hope PTK/ZK does is block the receptor from working, sort of like snipping the wires in the satellite dish. We're hoping this drug keeps the cancer from growing, makes it more sensitive to the chemotherapy we're giving and maybe even makes the tumor shrink by itself."
The studies are open at UCLA's Jonsson Cancer Center in Westwood, as well as at UCLA oncology practices in Santa Monica, Pasadena and Santa Clarita.