Human Monoclonal Antibody Helps Fight Advanced Melanoma Posted Tuesday, August 3, 2004 by arjuna
http://www.cancerwise.org/August_2004/print.cfm?id=6B104145-9ACE-4ABB-88FCF399BE506C90&method=DisplayFull
Early testing of an experimental human monoclonal antibody has shown a striking benefit in patients with advanced melanoma, according to M. D. Anderson researchers.
Tumors disappeared in three of 39 patients who were given a single injection of CP-675,206, a human monoclonal antibody manufactured by Pfizer Inc. Tumors shrank in a fourth patient, and cancer stopped growing in five other patients. These responses have remained since the patients’ initial treatment, which ranged from 13 to 28 months ago.Dr. Luis Camacho Photo
Most of the patients in the clinical trial had advanced melanoma, which has a median survival of less than a year, says the study’s principal investigator, Luis Camacho, M.D., assistant professor in M. D. Anderson’s Department of Melanoma Medical Oncology and a member of the institution’s Phase I Clinical Trials Group.
“We were very pleasantly surprised to find such objective antitumor responses in a Phase I clinical trial, which is designed to find the ideal dose and to look for side effects,” Camacho says. “These results are very early, but they are encouraging to us because there are no good agents available to treat malignant melanoma once it has spread.”
Tolerable side effects
Researchers gradually increased the amount of the initially tested dose by 1,500 fold, evaluating seven different dose levels, before they found higher doses that both produced a response and had tolerable side effects. Most patients who didn’t respond to the drug were those treated with lower doses, the investigators say.
The study was conducted at M. D. Anderson and at the University of California, Los Angeles. A collaborating researcher is Jesus Gomez Navarro, M.D., clinical director of the monoclonal antibody program at Pfizer Inc., which developed the antibody and is sponsoring the clinical trial. The researchers presented their findings at the annual meeting of the American Society of Clinical Oncology in June.
Similar to vaccines, CP-675,206 seems to continue to work long after patients receive the single two- to four-hour injection, Camacho says. “We believe the monoclonal antibody enlists the immune system to fight any new cancer cells trying to grow,” he says.
The antibody may work particularly well in melanoma, he adds, because previous research has shown the immune system, if activated, can recognize this cancer.
Because the antibody allowed the immune system to attack cells that “looked” similar to the body’s own, researchers worried that it could produce autoimmune disorders such as rheumatoid arthritis. But the only side effects observed, including rashes and diarrhea, occurred at the highest doses and were resolved without long-term problems, Camacho says.
Based on the results, Pfizer has launched a Phase II study, which is enrolling 100 patients at seven institutions nationwide. Camacho also serves as the principal investigator for this trial.
For more information about the Phase II multiple-dose CP675,206 study for patients with previously treated metastatic melanoma, call study coordinator Charla Parker, RN, at (713) 745-1042 or data manager Carolina Guitierrez, M.D., at (713) 794-1022.