Anti-idiotype induction therapy: anti-CA125 antibodies (Ab3) mediated tumor killing in patients treated with Ovarex mAb B43.13 (Ab1).

Intravenous injection of the murine monoclonal anti-CA125 antibody B43.13 (Ovarex: Ab1) into ovarian cancer patients led to the induction of an idiotypic network. Of the 75 patients who received one to ten injections of a 2-mg dose of the antibody, 48 developed anti-(mAb B43.13) antibodies (Ab2); 18 of these patients also had elevated levels of anti-[anti-(mAb B43.13)] antibodies (Ab3; = anti-CA125 antibodies) compared to pre-injection values. Characterization of these antibodies revealed that the binding to CA125 could be inhibited by mAb B43.13 in most samples. Human anti-CA125 antibodies or Ab3 purified from patient serum samples specifically recognized human ovarian tumor cells and tissues expressing CA125. In addition, these anti-CA125 antibodies were able to conduct Fc-mediated tumor cell killing (antibody-dependent cell-mediated cytotoxicity). This raises the possibility of using an Ab1 for anti-idiotype induction immunotherapy of cancer.