NASHVILLEIn a phase II study of an investigational monoclonal antibody, OvaRex MAb, in advanced recurrent ovarian cancer, 6 of 13 patients survived 50 weeks or longer from entry into the trial, Thomas G. Ehlen, MD, said at a poster session of the 32nd Annual Meeting of the Society of Gynecologic Oncologists (SGO).
Dr. Ehlen was the lead investigator of the trial at the Vancouver Cancer Center, British Columbia. The study was sponsored by AltaRex Corp., Waltham, Massachusetts.
The study enrolled 13 patients with advanced ovarian cancer that had relapsed after treatment failure of multiple standard therapies. Patients received intravenous 2-mg infusions of OvaRex MAb on an outpatient basis (five doses over a 12-week period, and then every 3 months until disease progression).
Over half of the patients in the study showed a substantive immune response following OvaRex MAb treatment, Dr. Ehlen said. Among these immune responders, one patient survived more than 18 months, and two are still alive almost 2 years after entry into the study.
In addition, Dr. Ehlen stated, OvaRex MAb was well tolerated, and treatment was easily managed in the outpatient setting.
Dr. Ehlen said that OvaRex MAb is antigen specific rather than tumor specific. "It targets the antigen CA 125, which is produced by most ovarian tumors but is not recognized by the patient’s immune system as a threat since it is self-produced," he said. "OvaRex MAb binds to the circulating CA 125, and because of its foreign nature, it fools the body’s own immune system, including the T cells, into attacking the CA 125 and, in turn, the associated ovarian tumor."
The frequent development of immune responses observed in the study, which correlated with evidence of prolonged disease stabilization and survival in some patients, provides further proof of principle for this approach to cancer treatment, Dr. Ehlen commented.
The study is one of several prospective, controlled trials sponsored by AltaRex in North America to evaluate the safety and efficacy of OvaRex MAb. By the end of the year, AltaRex hopes to file a Biologics License Application with the US Food and Drug Administration for regulatory approval of OvaRex MAb for ovarian cancer indications. The agent has already received Orphan Drug status and Fast Track designation from the FDA.