Definition

A contrast agent composed of a peptide of seven amino acids targeting the extradomain B (EDB) of fibronectin (FN) conjugated to the contrast agent gadolinium, with potential contrast-enhancing activity upon magnetic resonance (MR) imaging. Upon administration of EDB-FN-targeting gadolinium-based contrast agent MT218, the EDB-FN-targeting peptide moiety targets and binds to EDB-FN overexpressed on various tumor cells. Upon MRI, gadolinium produces a large magnetic moment and thus a large local magnetic field. This enhances the relaxation rate of nearby protons and increases the signal intensity of tissue images. This allows visualization and specific localization of EDB-FN-expressing tumor cells. EDB of fibronectin, an oncogenic extracellular matrix protein, is expressed in many aggressive solid human tumors, whereas it is not detectable in normal vessels and tissues.