Novel agents in targeted radionuclide therapy

Cadherins are cell adhesion and cell signaling molecules that provide the molecular link between adjacent cells, and have critical prescription for initiation and continuation of the adhesion mechanism. N-cadherin, which is a member of the cadherin family, is extensively presented in enlarged blood vessels of tumor cells and tumors. N-cadherin antagonists are vascular targeting agents with antineoplastic and antiangiogenic activity. These agents bind to the N-cadherin receptor in a selective and competitive manner and by this way inhibit tumor vasculature and tumor cell growth, also induce endothelial cell apoptosis induction of tumor cells. As part of this thesis, it is aimed to synthesize a new generation of peptide radiopharmaceuticals that can be applied on the theranostic platform to target N-cadherin present in tissues and cells where epithelial-mesenchymal transformation has taken place and evaluate this agent in vitro and in vivo. For this purpose, a synthetic N-Ac-CHAVC-NH2 cyclic peptide sequence, designed as (ADH-1)c, was synthesized which functions as an N-cadherin antagonist containing a selective binding His-Ala-Val (HAV) motif based on the chimeric antigen receptor sequence. A microwave-assisted solid phase peptide synthesis system based on the Fmoc chemistry was used for raising the yield and reducing the amount of racemization in the peptide synthesis. (ADH-1)c was synthesized by i → i + 5 macrocyclization using ammonium acetate (5% w/v) after synthesis and characterization of the linear counterpart (ADH-1). For the characterization and purification, liquid chromatographic-electrospray ionization-mass spectrometry (LC-ESI-MS) and reverse phase-high performance liquid chromatography (RP-HPLC) were used respectively. The conjugate of cyclic peptide and EDTA chelator (AntiCAD1) was synthesized by the water-soluble carbodiimide method. For the characterization of the AntiCAD1 agent the fluorescence spectrophotometer, zetasizer and LC-ESI-MS systems were used. The identified AntiCAD1 has been labeled with [68Ga]Ga radionucleotides. The [68Ga]Ga-AntiCAD1 analytical radiochemical purity was analyzed by TLC methods. In order to determine the analytical lipophilicity, the P dispersion coefficient was calculated and the 'shake flask' method was applied (logP=-2.69±0.54). Analytical biodistribution was investigated using PET/CT on Wistar Albino rats. Mean values of SUVmax were 1.36, 1.96, 1.38, 1.16 and 2.14 in the liver, kidney, spleen, salivary gland, and target lesion areas, respectively. The statistical Pearson Factor calculation method was used to test the relationship between the agent's target region and other body tissues and to measure the degree of this association. The correlation coefficient was calculated to be 0.73. This value, which ranged from 0.70 to 0.89, was interpreted as a strong positive correlation. In this study; identified that radio-labeled conjugate [68Ga]Ga-AntiCAD1 derived from the ADH-1 peptide - an adhesion molecule which is one of the cancer epithelial mesenchymal transformation markers can be used as a potential radiopharmaceutical in imaging cadherin activity in damaged tissues in which the increase of N-cadherin protein presentation has been identified and metastatic solid tumors with increased expression of the adhesion molecule. Because the study was designed on a terranostatic platform, it was concluded that the conjugate could be used for analogue therapy if it was marked with therapy radionuclides.