Successful therapy of human cancer with monoclonal antibodies (moAbs) has not yet been achieved, but remains a possibility. We have developed a method of moAb modification that should greatly enhance their specific toxicity when used for regional immunotherapy. Examples of appropriate clinical situations are intraperitoneal injection for ovarian carcinoma and intraspinal injection for tumors confined to cerebrospinal fluid. Such regional therapy may provide the added specificity required to allow tumor eradication to be obtained. By conjugating galactose directly to moAbs, very rapid blood clearance is produced via the hepatic galactose-specific receptor. Within minutes, essentially all of the moAb is taken up by the liver, and subsequently is rapidly degraded within hours. By this mechanism, the moAB is inactivated immediately upon entering the systemic circulation. Antigen binding activity is retained in such galactose conjugates, at least with the three moAbs tested. Also, complement-mediated cytotoxicity is unaffected. In this proposal, we intend to examine other effector functions of such conjugated moAbs; namely antibody- dependent cell-mediated cytotoxicity mediated by mouse lymphocytes, mouse macrophages or human lymphocytes, specific localization to human tumor xenografts in nude mice, and therapeutic effects on human tumor xenografts. In vivo experiments will utilize 4 human tumor cell lines which grow intraperitoneally in nude mice, as a model for ovarian carcinoma. Another, unique model that will be used is a transfected mouse cell line, 2.2, which expresses a single human membrane antigen, MA149, and which grows i.p. in syngeneic normal mice. If certain effector functions are partially lost, the conjugation procedure will be modified such that they are preserved. If necessary, a carrier molecule such as albumin or amino-dextran will be galactose-conjugated, then linked to moAbs at a 1:1 molar ratio. MoAbs of different classes and subclasses will be tested, including IgM, IgG2a, and IgG2b. Rapid blood clearance of moABs, after regional injection, has 2 major benefits. First, it will greatly reduce the reaction of moAbs with antigen- positive normal cells outside the region injected, which allows clinical use of moAbs that are not tumor-specific, but have other desirable characteristics, such as homogenous expression and high antigen density. Second, for moAbs conjugated to toxic radioisotopes, it will greatly reduce exposure of bone marrow and other normal tissues due to circulating radioactivity.
