title: [99mTc]HYNIC-RGD for imaging integrin alphavbeta3 expression.
abstract: There has been increasing interest in peptides containing the Arg-Gly-Asp (RGD) sequence for targeting of alpha(v)beta(3) integrins to image angiogenesis. [(18)F]Galacto-RGD has been successfully used for positron emission tomography applications in patients. Here we report on the preclinical characterization of a (99m)Tc-labeled derivative for single-photon emission computed tomography. c(RGDyK) was derivatized with HYNIC at the amino group of the lysine [c(RGDyK(HYNIC)) or HYNIC-RGD]. (99m)Tc labeling was performed using coligands (tricine and EDDA), as well as (99m)Tc(CO)(3)(H(2)O)(3). Radiolabeled peptides were characterized with regard to lipophilicity, protein binding and stability in buffer, serum and tissue homogenates. Integrin receptor activity was determined in internalization assays using alpha(v)beta(3)-receptor-positive M21 and alpha(v)beta(3)-receptor-negative M21L melanoma cells. Biodistribution was evaluated in normal and nude mice bearing M21, M21L and small cell lung tumors. HYNIC-RGD could be labeled at high specific activities using tricine, tricine-trisodium triphenylphosphine 3,3',3''-trisulfonate (TPPTS), tricine-nicotinic acid (NA) or EDDA as coligands. [(99m)Tc]EDDA/HYNIC-RGD, [(99m)Tc]tricine-TPPTS/HYNIC-RGD and [(99m)Tc]tricine-NA/HYNIC-RGD showed protein binding (<5%) considerably lower than [(99m)Tc](CO)(3)/HYNIC-RGD and [(99m)Tc]tricine/HYNIC-RGD. [(99m)Tc]EDDA/HYNIC-RGD revealed high in vitro stability accompanied by low lipophilicity with a log P value of -3.56, comparable to that of [(18)F]Galacto-RGD. In M21 cells for this compound, the highest level of specific and rapid cell uptake (1.25% mg protein(-1)) was determined. In vivo, rapid renal excretion, low blood retention, low liver and muscle uptakes and low intestinal excretion 4 h postinjection were observed. Tumor uptake values were 2.73% ID/g in M21 alpha(v)beta(3)-receptor-positive tumors versus 0.85% ID/g in receptor-negative tumors 1 h postinjection. Small cell lung tumors could be visualized using gamma camera imaging. [(99m)Tc]EDDA/HYNIC-RGD shows encouraging properties to target alpha(v)beta(3) receptors in vivo with high stability and favorable pharmacokinetics. Tumor uptake studies showed specific targeting of alpha(v)beta(3)-receptor-positive tumors with tumor-to-organ ratios comparable to those of [(18)F]Galacto-RGD.
authors.affiliation: Department of Nuclear Medicine, Medical University of Innsbruck, A-6020 Innsbruck, Austria. clemens.decristoforo@uibk.ac.at <clemens.decristoforo@uibk.ac.at>
authors.forename: Clemens
authors.initials: C
authors.lastname: Decristoforo
authors.forename: Bluma
authors.initials: B
authors.lastname: Faintuch-Linkowski
authors.forename: Ana
authors.initials: A
authors.lastname: Rey
authors.forename: Elisabeth
authors.initials: E
authors.lastname: von Guggenberg
authors.forename: Marco
authors.initials: M
authors.lastname: Rupprich
authors.forename: Ignacio
authors.initials: I
authors.lastname: Hernandez-Gonzales
authors.forename: Teodoro
authors.initials: T
authors.lastname: Rodrigo
authors.forename: Roland
authors.initials: R
authors.lastname: Haubner
mesh_terms: D000818:Animals; D018288:Carcinoma, Small Cell / Q000000981:diagnostic imaging / Q000378:metabolism; D045744:Cell Line, Tumor; D004355:Drug Stability; D006801:Humans; D006834:Hydrazines / Q000378:metabolism*; D039302:Integrin alphaVbeta3 / Q000032:analysis* / Q000378:metabolism; D008175:Lung Neoplasms / Q000000981:diagnostic imaging / Q000378:metabolism; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C; D009539:Nicotinic Acids / Q000378:metabolism*; D009842:Oligopeptides / Q000378:metabolism*; D015609:Organotechnetium Compounds / Q000378:metabolism*; D010456:Peptides, Cyclic / Q000378:metabolism*; D011485:Protein Binding; D011877:Radionuclide Imaging; D019275:Radiopharmaceuticals / Q000378:metabolism*; D014018:Tissue Distribution
chemical_list: C120392:6-hydrazinopyridine-3-carboxylic acid; D006834:Hydrazines; D039302:Integrin alphaVbeta3; D009539:Nicotinic Acids; D009842:Oligopeptides; D015609:Organotechnetium Compounds; D010456:Peptides, Cyclic; D019275:Radiopharmaceuticals; C585528:technetium 99m HYNIC-RGD; C047981:arginyl-glycyl-aspartic acid