In a recently completed phase II study of the monoclonal antibody OvaRex, nearly half of the OvaRex-treated patients with advanced ovarian cancer survived 50 weeks or longer. The results of the trial were presented at the 32nd Annual Meeting of the Society of Gynecologic Oncologists by Thomas G. Ehlen, MD, FRCSC, lead investigator of the clinical trial at the Vancouver Cancer Center in British Columbia. Patients participating in this study had had a relapse of ovarian cancer after failure of multiple standard treatments.
The study enrolled 13 patients with advanced recurrent ovarian cancer who received 2-mg intravenous infusions of OvaRex on an outpatient basis (five doses over a 12-week period and then every 3 months until disease progression). Six patients survived 50 weeks or longer. Over half the patients achieved immune responses following treatment. 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, OvaRex was well tolerated, and treatment was easily managed in the outpatient setting.
New Treatments Needed
"For women with advanced ovarian cancer who have relapsed disease after treatment with standard chemotherapeutic agents, the response benefit from available drug treatment is commonly less than 1 year and is often associated with significant toxicities," said Dr. Ehlen. "We need new treatments that do not have the same side effects as currently used chemotherapies, and so the clinical results from this and other completed or ongoing trials with OvaRex are very encouraging."
Rather than being tumor specific, OvaRex is an antigen-specific product, Dr. Ehlen explained. "It targets the antigen CA-125, which is produced by most ovarian tumors but not recognized by the patient’s immune system as a threat since it is self-produced," he continued. "OvaRex 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. Among the patients followed in our study, it was notable that two patients continue to survive years after starting the protocol therapy."
Several Clinical Trials Underway
"We believe that the frequent development of immune responses observed in this study—correlated with evidence of prolonged stabilization of disease and survival in some patients—provides further proof of principle for this innovative approach to cancer treatment," commented Howard Finger, MD, vice president of clinical operations and medical director of AltaRex Corp, the manufacturer of OvaRex. "We are pleased with the outcomes of this completed study, one of several prospective, well-controlled trials in North America sponsored by AltaRex to evaluate the safety and efficacy of OvaRex MAb to support our upcoming US regulatory filing for ovarian cancer indications."
Currently, these late-stage clinical studies are underway at 64 sites across North America. The studies involve patients in both the watchful waiting and recurrent ovarian cancer indications. Worldwide, OvaRex has been studied in more than 400 ovarian cancer patients.
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