Treatment with a murine monoclonal antibody directed against CA 125 often induces a broad immune response that correlates with prolonged survival of women with recurrent ovarian cancer, according to a report in the July issue of the American Journal of Obstetrics and Gynecology.
MAb-B43.13 (OvaRex Mab, oregovomab, AltaRex Corp., Edmonton, Alberta, Canada) is a murine immunoglobulin G-1 antibody to CA 125. Prolonged survival was an unexpected outcome when technicium-99m-labeled MAb-B43.13 was first administered as a diagnostic agent to women with recurrent ovarian cancer, Dr. Volker J. Mobus of Statische Kliniken in Frankfort, Germany, and colleagues report.Subsequently, 44 patients were treated with Tc-99m-labeled MAb-B43.13 between 1989 and 1996. The women had already undergone up to five chemotherapeutic regimens, and based on median serum level of CA 125 antigen of 316 U/mL, were considered to have a very poor prognosis. For this the study, they were given up to seven i.v. injections of 2 mg each.More than half of the patients survived for more than 1 year after the first dose, and about a third for more than 2 years. Six patients were still living after 4 to 7.5 years. Patients generally required multiple injections to experience robust humoral responses, the authors note. Those who were treated at least three times and who had a broad, multiepitopic immune response maintained that response for more than 1 year.Survival was significantly greater among those who exhibited a human antimurine antibody (HAMA) response (p = 0.0016). There was a trend toward greater survival among those with a response to variable region Ab2 or anti-CA 125, as well. Among those with evaluable immune responses who survived for more than 2 years, 86.7% were HAMA responders, 90% were Ab2 responders, and 45.5% were anti-CA 125 antibody responders.The immune therapy had a benign safety profile, the report indicates, and was not associated with significant toxicities. ‘The favorable safety profile of Mab-B43.13, combined with its therapeutic efficacy, may render it an important additive to the currently available treatment options for ovarian cancer,’ Dr. Mobus and colleagues conclude.(Source: Am J Obstet Gynecol 2003;189:28-36: Reuters Health: July 28, 2003: Oncolink)