Design and synthesis of small molecule ligands targeting protease-activated receptor 2 as potential diagnostic and therapeutic agents

Abstract

Positron emission tomography (PET) imaging requires radionuclides (positron-emitters) labeled molecules (tracers) to image biochemical and physiological processes in vivo and helps diagnose diseases noninvasively. The success of PET imaging depends on validated radiopharmaceuticals targeting biologically relevant receptors. Protease-activated receptors (PARs) are cell membrane receptors that belong to a class of the G protein-coupled receptors (GPCRs) family. Proteaseactivated receptor 2 (PAR2) is the second member of the PARs family. Aberrant activation of PAR2 is associated with various cancers, through downstream signaling that contributes to cancer progression and tumor metastasis. It has been found that PAR2 exhibited up to 16-fold overexpression in lung cancer. The upregulation of PAR2 in cancers indicates that it may serve as potential drug target for cancer screening and treatment. Blocking PAR2 activity with small molecules is proposed to provide a therapeutic benefit. In addition, the development of 18Fradiolabeled small molecules targeting PAR2 receptor hasthe potential to non-invasively diagnose some types of cancers such as lung and breast cancers. A library of AZ3451 analogues (14 compounds) was designed with the assistance of molecular modelling, and was synthesized, and characterized by Mass Spectrometry, and 1H-NMR. All compounds have greater than 95% purity as confirmed by HPLC. Collaborator Dr. Rithwik Ramachandran at Western University (UWO) will perform functional assays including calcium-signalling, β-arrestin recruitment, MARK signaling assays etc. to evaluate all compounds for the therapeutic potential; the candidate molecule will be selected for radiolabelling and PET imaging studies using animal models of cancer at the TBRHRI. The novel compounds synthesized in the thesis are potentially useful for the treatment of PAR2-driven cancers while the radioligand has potential for non-invasive cancer diagnosis with PET.