Evaluation of Glycodendron and Synthetically Modified Dextran Clearing Agents for Multistep Targeting of Radioisotopes for Molecular Imaging and Radioimmunotherapy

A series of N-acetylgalactosamine-dendrons (NAG-dendrons) and dextrans bearing biotin moieties were compared for their ability to complex with and sequester circulating bispecific antitumor antibody streptavidin fusion protein (scFv4-SA) in vivo, to improve tumor-to-normal tissue concentration ratio...

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Published in:Molecular pharmaceutics 2014-02, Vol.11 (2), p.400-416
Main Authors: Cheal, Sarah M, Yoo, Barney, Boughdad, Sarah, Punzalan, Blesida, Yang, Guangbin, Dilhas, Anna, Torchon, Geralda, Pu, Jun, Axworthy, Don B, Zanzonico, Pat, Ouerfelli, Ouathek, Larson, Steven M
Format: Article
Language:English
Subjects:
Animals
Carbohydrate Sequence
Cell Line, Tumor
Colonic Neoplasms - diagnosis
Colonic Neoplasms - radiotherapy
Coordination Complexes - chemistry
Coordination Complexes - therapeutic use
Dextrans - chemistry
Dextrans - therapeutic use
Drug Delivery Systems
Drug Stability
Heterografts
Humans
Mice
Molecular Imaging
Molecular Structure
Positron-Emission Tomography
Radioimmunotherapy
Radioisotopes - chemistry
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Summary:A series of N-acetylgalactosamine-dendrons (NAG-dendrons) and dextrans bearing biotin moieties were compared for their ability to complex with and sequester circulating bispecific antitumor antibody streptavidin fusion protein (scFv4-SA) in vivo, to improve tumor-to-normal tissue concentration ratios for multistep targeted (MST) radioimmunotherapy and diagnosis. Specifically, a total of five NAG-dendrons employing a common synthetic scaffold structure containing 4, 8, 16, or 32 carbohydrate residues and a single biotin moiety were prepared (NAGB), and for comparative purposes, a biotinylated-dextran with an average molecular weight of 500 kD was synthesized from amino-dextran (DEXB). One of the NAGB compounds, CA16, has been investigated in humans; our aim was to determine if other NAGB analogues (e.g., CA8 or CA4) were bioequivalent to CA16 and/or better suited as MST reagents. In vivo studies included dynamic positron-emission tomography (PET) imaging of 124I-labeled-scFv4-SA clearance and dual-label biodistribution studies following MST directed at subcutaneous (s.c.) human colon adenocarcinoma xenografts in mice. The MST protocol consists of three injections: first, a scFv4-SA specific for an antitumor-associated glycoprotein (TAG-72); second, CA16 or other clearing agent; and third, radiolabeled biotin. We observed using PET imaging of the 124I-labeled-scFv4-SA clearance that the spatial arrangement of ligands conjugated to NAG (i.e., biotin linked with an extended spacer, referred to herein as long-chain (LC)) can impact the binding to the antibody in circulation and subsequent liver uptake of the NAG-antibody complex. Also, NAGB CA32-LC or CA16-LC can be utilized during MST to achieve comparable tumor-to-blood ratios and absolute tumor uptake seen previously with CA16. Finally, DEXB was equally effective as NAGB CA32-LC at lowering scFv4-SA in circulation, but at the expense of reducing absolute tumor uptake of radiolabeled biotin.
ISSN:1543-8384
1543-8392
DOI:10.1021/mp4003128