Design of a New 99mTc-radiolabeled Cyclo-peptide as Promising Molecular Imaging Agent of CXCR4 Receptor: Molecular Docking, Synthesis, Radiolabeling, and Biological Evaluation.

Abstract

C-X-C Chemokine receptor type 4 (CXCR4) is often overexpressed or overactivated in different types and stages of cancer disease. Therefore, it is considered a promising target for imaging and early detection of primary tumors and metastasis. In the present research, a new cyclo-peptide radiolabelled with 99mTc, 99mTc-Cyclo [D-Phe-D-Tyr-Lys (HYNIC)- D-Arg-2-Nal-Gly-Lys(iPr)], was designed based on the parental LY251029 peptide, as a potential in vivo imaging agent of CXCR4-expressing tumors. The radioligand was successfully prepared using the method of Fmoc solid-phase peptide synthesis and was evaluated in biological assessment. Molecular docking findings revealed high affinity (binding energy of -9.7 kcal/mol) and effective interaction of Cyclo [D-Phe- D-Tyr-Lys (HYNIC)-D-Arg-2-Nal-Gly-Lys(iPr)] in the binding pocket of CXCR4 receptor (PDB code: 3OE0) as well. The synthesized peptide and its purity were assessed by both reversed-phase high-performance liquid chromatography (RP-HPLC) and mass spectroscopy. High stability (95%, n = 3) in human serum and favorable affinity (Kd = 28.70 ± 13.56 nM and Bmax = 1.896 ± 0.123 fmol/mg protein) in the B16-F10 cell line resulted. Biodistribution evaluation findings and planar image interpretation of mice both showed high affinity and selectivity of the radiotracer to the CXCR4 receptors. Therefore, the findings indicate this designed radioligand could be used as a potential SPECT imaging agent in highly proliferated CXCR4 receptor tumors.