Pretargeted tumour imaging with streptavidin immunoconjugates of monoclonal antibody CC49 and 111In-DTPA-biocytin.

Pretargeted tumour imaging was performed in nude mice bearing subcutaneous LS174T human colon cancer xenografts with streptavidin-CC49 monoclonal antibody and 111In-DTPA-biocytin. Mice were administered 250 micrograms of streptavidin-CC49, followed 6 or 9 days later by 40 ng (250 microCi) of 111In-DTPA-biocytin. Tumors were visualized at 24 h postinjection of 111In-DTPA-biocytin. Tumour uptake was 0.9-2.5% injected dose/g with tumour/nontarget ratios from 2:1 to 37:1 (except for kidney, which was 0.5-3:1). Tumour uptake in mice pretargeted with streptavidin or streptavidin-conjugated nonspecific normal mouse IgG was < 0.1% i.d./g.