Selection of monoclonal antibody to hCG which localizes in human choriocarcinoma growing in the Syrian hamster cheek pouch.

Six different monoclonal antibodies (MAbs) to human chorionic gonadotropin (hCG) were evaluated for radioimmunodetection in Golden Syrian Hamsters bearing a human choriocarcinoma in the cheek pouch (188-516 mIU of hCG/g). The affinity of three antibodies when determined were high and five of the antibodies were of IgG1 subclass. After i.v. injection of Staphylococcus Protein A (SPA) affinity purified radioiodinated antibodies, tissue distribution studies demonstrated that antibody 061 had higher target-to-nontarget ratios than the other five antibodies. The mean tumor:muscle ratio of 131I-MAb 061 was 27.5 in four animals, where the mean tumor:muscle ratio of four animals injected with 131I-labeled control monoclonal IgG1 Kappa from MOPC-21 murine myeloma (MOPC-21) was only 2.2. Sharp images of the cheek pouch tumor were obtained at five days following a tracer dose of 131I-061 MAb, but not with the same dose of a 131I-MOPC-21.