99mTc-ior C5

Abstract

Monoclonal antibody (MAb) for C5 is a murine IgG 1 antibody which recognizes the tumor-associated antigen (TAa) for C2 homogeneously expressed in the cytoplasm of normal colon epithelium and beterogeneously expressed in more than 83% of primary colorectal carcinomas. The antigen for C2 appears distinct in molecular structure and tissue expression compared to other colorectal antigens in that the latter are more strongly expressed in colon cancers compared to corresponding normal tissues and the expression in both normal colonic mucosa and colorectal carcinomas is homogeneous. In vivo biodisinbution studies have shown no uptake in normal organs and tissues, and studies in human colon cancer xenograft-bearing nude mice have shown good tumor uptake after antibody administration. Biodistribution studies in patients indicated that for C2 was highly expressed in primary and metastatic colorectal carcinomas and showed very limited expression in normal adult tissues. Based on data from pharmacokinetics and biodistribution studies. 9 9 m Tc-ior C5 appears to be useful as a target for the immunodiagnosis of colorectal tumors. Furthermore, feasibility studies indicate that 9 9 m Tc-ior C5 can be used safely and that adequate tumor-localizing doses can be administered for diagnostic imaging without exposing the patient to excessive radiation.