Tumor localization of monoclonal antibodies against human renal carcinoma in a xenograft model

We investigated the localization of intravenously injected DAL K45 and DAL K29, two monoclonal antibodies (MABs) against human renal cell carcinoma (RCC), and their F(ab) 2 fragments in nude mice bearing intrarenal transplants of the RCC line Caki-1. More of the MABs or their F(ab) 2s specifically localized in the tumor than in any normal tissue with the exception of blood. Compared to parent MABs, F(ab) 2s were cleared faster from all tissues. In serum, the MABs and F(ab) 2s showed a single radioactive peak retaining partial immunoreactivity. DAL K45-F(ab) 2 showed the highest tumor:normal tissue localization ratios and the most distinct gamma-camera image at 24 h.