Ligands of the Angiotensin II Type 2 Receptor : Exploring structure and function of the AT2R ligand C38

Sammanfattning: The renin-angiotensin-aldosterone-system (RAAS) control blood-pressure regulation, exerted by the main effector peptide angiotensin II (AngII) binding the angiotensin II type 1 receptor (AT1R). While hypertension is the most known disease caused by over-activity in RAAS, several proteins in the system exhibit protective functions.One of these protective proteins is the GPCR angiotensin II type 2 receptor (AT2R). After decades of research its biological role remain to be fully elucidated, exemplified by the two AT2R ligands currently in clinical trials; agonist C21 for treatment of idiopathic pulmonary fibrosis, and antagonist EMA401 for treatment of peripheral neuropathic pain. Making a minor structural change in C21 shifted the pharmacological profile, generating the regioisomer antagonist C38. The renewed interest in AT2R antagonists as potential drugs to treat neuropathic pain make continued studies of antagonist C38 highly interesting. The aim of this thesis was to continue exploring the structure-activity relationship of antagonist C38 by investigating three chemical motifs to identify compounds with better drug-like properties. Developing a new chemical method, transesterification of sulfonyl carbamates, allowed quick modification of one of the motifs. Reducing the length of the sulfonyl carbamate chain significantly increased metabolic stability in liver microsomes without losing affinity for AT2R. Using a model substrate, the transesterification reaction was applied in a microwave heated continuous-flow system.Adding small substituents to the central phenyl ring generated a second library of ligands with retained affinity, but with no observed increase in metabolic stability. Docking studies with this library and a recently presented crystal structure of AT2R, resulted in a proposed binding mode of C38. Replacing the imidazole head group with bicyclic amides slightly improved affinity. While metabolic stability improved compared to previously published amide analogs, the bicyclic ligands were inferior to C38. Developing an assay based on RAW264.7 macrophages allowed a new evaluation of the functional activity exhibited by C38. In contrast to previous research, C21 and C38 both display agonistic functional activity in the macrophage assay.In summary, the work presented in this thesis expand the structure-activity relationship of C38 and its pharmacological profile. Two new ligands were identified that could serve as tools in murine models of neuropathic pain.