[99mTc]HYNIC-RGD for imaging integrin αvβ3 expression

Decristoforo, Clemens; Faintuch-Linkowski, Bluma; Rey, Ana; von Guggenberg, Elisabeth; Rupprich, Marco; Hernandez-Gonzales, Ignacio; Rodrigo, Teodoro; Haubner, Roland

doi:10.1016/j.nucmedbio.2006.09.001

Next »Nuclear Medicine and Biology
Volume 33, Issue 8 , Pages 945-952, November 2006

[^99mTc]HYNIC-RGD for imaging integrin α_vβ₃ expression

Clemens Decristoforo
- Department of Nuclear Medicine, Medical University of Innsbruck, A-6020 Innsbruck, Austria
- Corresponding author. Universitaetsklinik fuer Nuklearmedizin, Anichstrasse 35, A-6020 Innsbruck, Austria. Tel.: +4351250480951; fax: +4351250422659.
Bluma Faintuch-Linkowski
- Radiopharmacy Center Instituto de Pesquisas Energeticas e Nucleares (IPEN), 05508-900 São Paulo, Brazil
Ana Rey
- Cátedra de Radioquímica, Facultad de Química, Universidad de la República, C.P. 11800 Montevideo, Uruguay
Elisabeth von Guggenberg
- Department of Nuclear Medicine, Medical University of Innsbruck, A-6020 Innsbruck, Austria
Marco Rupprich
- Department of Nuclear Medicine, Medical University of Innsbruck, A-6020 Innsbruck, Austria
Ignacio Hernandez-Gonzales
- Centro de Isotopos, Ciudad de la Habana, Cuba
Teodoro Rodrigo
- Radiopharmacy Center Instituto de Pesquisas Energeticas e Nucleares (IPEN), 05508-900 São Paulo, Brazil
Roland Haubner
- Department of Nuclear Medicine, Medical University of Innsbruck, A-6020 Innsbruck, Austria

Received 9 June 2006; received in revised form 4 August 2006; accepted 2 September 2006.

Abstract

There has been increasing interest in peptides containing the Arg–Gly–Asp (RGD) sequence for targeting of α_vβ₃ integrins to image angiogenesis. [¹⁸F]Galacto-RGD has been successfully used for positron emission tomography applications in patients. Here we report on the preclinical characterization of a ^99mTc-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]. ^99mTc labeling was performed using coligands (tricine and EDDA), as well as ^99mTc(CO)₃(H₂O)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 α_vβ₃-receptor-positive M21 and α_vβ₃-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. [^99mTc]EDDA/HYNIC-RGD, [^99mTc]tricine–TPPTS/HYNIC-RGD and [^99mTc]tricine–NA/HYNIC-RGD showed protein binding (<5%) considerably lower than [^99mTc](CO)₃/HYNIC-RGD and [^99mTc]tricine/HYNIC-RGD. [^99mTc]EDDA/HYNIC-RGD revealed high in vitro stability accompanied by low lipophilicity with a log P value of −3.56, comparable to that of [¹⁸F]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 α_vβ₃-receptor-positive tumors versus 0.85% ID/g in receptor-negative tumors 1 h postinjection. Small cell lung tumors could be visualized using γ camera imaging.

[^99mTc]EDDA/HYNIC-RGD shows encouraging properties to target α_vβ₃ receptors in vivo with high stability and favorable pharmacokinetics. Tumor uptake studies showed specific targeting of α_vβ₃-receptor-positive tumors with tumor-to-organ ratios comparable to those of [¹⁸F]Galacto-RGD.

Keywords: RGD, Technetium-99m, HYNIC, α_vβ₃