RT Journal Article SR Electronic T1 Imaging of Tumor Angiogenesis Using 99mTc-Labeled Human Recombinant Anti-ED-B Fibronectin Antibody Fragments JF Journal of Nuclear Medicine JO J Nucl Med FD Society of Nuclear Medicine SP 1707 OP 1716 VO 47 IS 10 A1 Dietmar Berndorff A1 Sandra Borkowski A1 Dieter Moosmayer A1 Francesca Viti A1 Beate Müller-Tiemann A1 Stephanie Sieger A1 Matthias Friebe A1 Christoph S. Hilger A1 Luciano Zardi A1 Dario Neri A1 Ludger M. Dinkelborg YR 2006 UL http://jnm.snmjournals.org/content/47/10/1707.abstract AB The aim of this study was to target the angiogenesis-associated extracellular matrix protein ED-B fibronectin for molecular imaging of solid tumors. Recombinant and chemically modified derivatives of the single-chain antibody fragment (scFv) L19, capable of being labeled with 99mTc, were synthesized and radiolabeled. The resulting compounds 99mTc-AP39, 99mTc-L19-His, and 99mTc-L19-Hi20 were assessed for their imaging properties in vivo. Methods: L19 was genetically modified by inserting either the (Gly)3-Cys-Ala (AP39) or a (His)6 tag (L19-His) sequence at the C-terminal end. Chemical modifications were performed by conjugating the bifunctional chelator Hi20 (L19-Hi20) at ε-Lys-NH2 residues of the molecule to allow for a direct chelator-based labeling with 99mTc. Tumor-targeting, pharmacokinetic, and scintigraphic imaging properties of the radiolabeled scFvs were evaluated in nude mice bearing murine F9 teratocarcinoma. Results: 99mTc labeling of the L19 derivatives yielded radiochemically pure proteins maintaining high immunoreactivity to ED-B fibronectin, as measured by affinity chromatography. Size-exclusion high-performance liquid chromatographic analysis of labeled L19 derivatives demonstrated either dimeric species (L19-His) or a mixture of predominantly associative dimeric and monomeric species (AP39, L19-Hi20). 99mTc-AP39 showed the most favorable biodistribution and imaging properties with high and fast tumor uptake (8.3 percentage injected dose per gram at 3 h after injection), rapid blood clearance and renal excretion, leading to high signal-to-noise ratios (tumor-to-blood ratio of 6.4 at 3 h after injection), and excellent planar scintigraphy in vivo. Conclusion: ED-B fibronectin can be efficiently targeted by 99mTc-AP39 and scintigraphically visualized in tumor-bearing mice, providing a potentially useful clinical tool for imaging of angiogenesis-associated ED-B fibronectin–expressing human tumors.