In vivo optical imaging using a novel fluorescently-labeled single-domain antibody targeting a universal tumor marker

Fluorescence molecular imaging plays an essential role in clinical applications such as image-guided surgery by aiding surgeons in localizing and identifying tissues to resect or to preserve during oncological surgery. This technology relies increasingly on the use of targeted fluorescent agents that recognize specific biomarkers expressed by diseased or healthy tissue. Targeting moieties such as camelid-derived single-domain antibodies (sdAbs), characterized by high target affinity and fast systemic clearance, are excellent candidates for molecular imaging. Due to their mid-range size (~12-15 kDa), they offer considerable advantages over small molecules, peptides, and antibodies.

Within this project, we generated, developed, and preclinically validated a panel of sdAbs with view of application in molecular-guided surgery. First, we present the capabilities of the generated sdAbs to bind on multiple types of cancer cells in vitro. Further, we report in vivo biodistribution and specific tumor binding of the sdAbs after radiolabeling (99mTc) in the subcutaneous tumor model in mice. Finally, we show the in vivo behavior and the capacity of the selected sdAbs to allow specifically visualize cancer tissue after conjugation of a novel fluorescent molecule (S775Z) in subcutaneous and orthotopic tumor models with clinically relevant target-to-background-ratios. We conclude that the generated compounds show a potential towards future clinical translation, for example as a contrast agent for image-guided surgery. This application could increase the accuracy of detection and removal completeness of number of cancers.