The generation of MAb3 directed against human breast tu mor-associated cell surface antigens offers the potential for improved techniques in the evaluation of patients with cancer

Thirteen patients with metastatic breast carcinoma were given injec dons of 50—1593@ag of †̃311-monoclonal antibody (MAb) B6.2 immuno globulin G and F(ab')@for pharmacokinetic evaluation and radioimmu noimaging. Blood clearance of the †̃31I-MAb-B6.2 was biphasic. The mean half-times (t@, t@.,)for the immunoglobulin G were 33 ±1.7 and 20.9 ±11.0 h, respectively. The t@ for the F(ab'>@was 1.7 ±1.3 h, and the t@ was 31.0 ±5.7 h. The percentageof protein bound †̃@†̃I for the immunoglobulin G and for the F(ab')@ at 72 h was 73.7 ±11.4% and 58.2 ±14.5%, respectively. In vitro reactivity of MAb B6.2 with granu locytes isolated from normal subjectsand patients was demonstratedby cytofluorometric and radioimmunoassays.MAb B6.2 wasshownto bind with normal cross-reactingantigen, a cell surface antigen known to be expressedon normal humangranulocytes.Reactivity with normal cross reacting antigen on granulocytes is consistent with the skeletal images obtainedduring immunoscintigraphy of all 13 patients. A specific tumor image was observed in one patient. No toxicity was encountered. In spite of extensive preclinical data suggestingthat †̃31I-MAb B6.2 would be a useful agent for radioimmunoimaging, the clinical utility of this reagent is probably limited because of the reactivity with granulocytes.