Intraperitoneal radio‐localization of tumors pre‐targeted by biotinylated monoclonal antibodies

Abstract

We describe 2-step and 3-step strategies for intraperitoneal tumor radio-localization by means of monoclonal antibodies (MAbs). Nude mice bearing intraperitoneal human colon carcinoma tumors were injected i.p. with biotinylated MAb AUAI, followed 24 hr later by radioiodinated streptavidin (2-step). The uptake of radioactivity in tumor and normal tissues was measured 4 hr after injection of radioactive compound. A 3-step strategy consisted in administering biotinylated antibody, cold avidin after 24 hr and 111In-labelled biotin after a further 4 hr; mice were then killed 2 hr later. Tumor localization of intraperitoneally-administered biotinylated antibody and direct targeting of radioactive streptavidin to biotinylated antibody bound to tumor sites were demonstrated using immunohistochemistry and autoradiography. Our results show that (i) the 2-step approach increased the percentage of radioactivity uptake by tumor with respect to directly labelled antibodies (24% vs. 6%) and improved the tumor/non-tumor ratio; (ii) the 3-step approach allowed faster blood clearance of the radioactive probe (111In-biotin) and yielded high tumor/non-tumor ratios. "Pre-targeting" methods appear to have advantages over the conventional 1-step approach with directly radiolabelled antibody.

Biochemical modifications of avidin improve pharmacokinetics and biodistribution, and reduce immunogenicity

“…Approximately 10% of avidin's mass is due to heterogeneous oligosaccharides, largely composed of mannose and N-acetylglucosamine (DeLange, 1970;Bruch and White, 1982). Because of their high affinity for biotin, they have been used in numerous biotechnological applications Bayer, 1988, 1989) and in different in vivo procedures such as radioimmunodetection and drug immunotargeting (Hnatowich et al, 1987;Paganelli et al, 1990Paganelli et al, , 1995. Radiolabelled AV and SA show different plasma pharmacokinetics and in vivo behaviours (Rosebrough, 1993;Sung et al, 1994;Grana et al, 1996).…”

Polyethylene glycol modification of a galactosylated streptavidin clearing agent: effects on immunogenicity and clearance of a biotinylated anti-tumour antibody

“…Pretargeting strategies using streptavidin or avidin either as the carrier of the radioisotope to a tumour pretargeted with biotinylated antibody (Paganelli et al, 1992;Khawli et al, 1993;Saga et al, 1994) or as the clearing agent for biotinylated antibodies before administration of the radioisotope in three-step pretargeting (Paganelli et al, 1990b(Paganelli et al, , 1991a have also been described as successfully reducing the blood background levels of radioactivity.…”

Distribution of neocarzinostatin conjugated to biotinylated chimeric monoclonal antibody Fab fragments after adminstration of avidin

“…However, with the avidin doses used in this study, we did not observe any side-effects in the animals. Other researchers have also reported that such doses of avidin are not toxic (Hnatowich et al, 1987;Ogihara et al, 1994;Paganelli et al, 1990).…”