Radiolabeling and biological evaluation of the GX1 and RGD-GX1 peptide sequence for angiogenesis targeting

• Published in: Nuclear medicine and biology 2015-02, Vol.42 (2), p.123-130
• Main Authors: Oliveira, E.A, Faintuch, B.L
• Format: Article
• Language: English
• Subjects: Amino Acid Sequence; Angiogenesis; Animals; Blood Proteins - metabolism; Chelating Agents - chemistry; Dimerization; Drug Stability; Humans; Hydrazines - chemistry; Isotope Labeling; Mice; Mice, Inbred BALB C; Molecular Imaging; Neovascularization, Pathologic - diagnosis; Nicotinic Acids - chemistry; Oligopeptides - chemistry; Oligopeptides - metabolism; Oligopeptides - pharmacokinetics; Radiochemistry; Radiology; RGD and GX1 peptides; Technetium; Technetium-99 m; Tissue Distribution
• ISSN: 0969-8051; 1872-9614
• DOI: 10.1016/j.nucmedbio.2014.09.004

Abstract Introduction Aiming to develop a novel99m Tc-labeled imaging agent, for angiogenesis and tumor receptors, two peptides obtained from phage display library, namely GX1 and the heterodimer RGD-GX1, were synthesized in a cyclic conformation. They were radiolabeled with99m Tc, employing the HYNIC chelator, for radiochemical evaluation and biological properties. Methods Radiolabeling, radiochemical control, plasma protein binding, and partition coefficient were assessed for both radioconjugates. Biodistribution in healthy Balb/c mice was carried out, in order to evaluate the biological behaviour of the radiocomplexes. Results The conjugates displayed a rather similar pharmacokinetic profile. They were prepared with high radiochemical purity (> 96%), and both were hydrophilic (log P of − 2.25 and − 2.51 respectively). Preferential renal excretion was observed. Kidney uptake (42.31 ± 5.35 %ID/g) for99m Tc-HYNIC-E-[c(RGDfk)-c(GX1)], 1 h post-injection was about three times higher than the uptake of99m Tc-HYNIC-PEG4 -c(GX1) (11.92 ± 4.77%ID/g). Total blood, bone and muscle values revealed a slightly slower clearance for the RGD-GX1 radiocomplex. Conclusion The high radiochemical purity achieved, and the similar in vivo profile observed for both radioconjugates, make them potential candidates for radiopharmaceuticals for tumor imaging. Further investigations of binding affinity, and uptake of GX1 and RGD-GX1 peptides in tumor models, are warranted.