Design, Synthesis and Characterization of Adenosine Receptor Ligands and Enzyme Inhibitors

The present PhD thesis focuses on different fields of adenosinergic system: heterocycles as A2AAR antagonists, nucleosides as partial A2AAR agonists, and nucleosides as A3AR agonists/antagonists. In the first section, novel therapeutic agents capable of synergistically inhibiting CK1δ isozymes while simultaneously antagonizing A2AAR for treating chronic neurodegenerative diseases and cancer were designed. Experimental and computational approaches to elucidate the key structural factors governing CK1δ inhibition and AR affinity were integrated to achieve this. Findings revealed that smaller substituents at 2 and 9-positions of adenine enhanced binding efficiency, while dynamic binding studies identified a “flipped” binding mode that optimized interactions with the selectivity pocket. Notably, the 9-cyclopentyl-2-dimethylamino-N6-methyl- (2-benzimidazolyl) adenine (17) emerged as the first dual A2AAR antagonist and CK1δ inhibitor, offering a promising multi-target therapeutic strategy. The second section synthesized a series of 2,8-disubstituted Ado derivatives through a multistep process to investigate novel A2AAR partial agonists for EV regulation in GBM cells. Structural modifications at 2 and 8-positions significantly influenced AR selectivity and binding affinity. Functional analyses demonstrated that 2-hexynyl-8-methylaminoAdo (1) acts as a partial agonist capable of regulating EV release, indicating its therapeutic potential in glioblastoma treatment. These findings underscore the crucial role of structural elements in receptor interactions and their implications for drug development. In the third section, the anticancer activity of A3AR ligands were explored by synthesizing known substituted Ado derivatives, which behave as A3AR antagonists, and a novel A3AR agonist N6-(2,2- diphenylethyl)-2-phenylethynylMECA (5) via a multistep process and analyzing its ligand-receptor interactions. Binding studies revealed a shift between antagonism and agonism due to modifications in sugar moiety. Cytotoxicity assays confirmed that these compounds effectively inhibited proliferation and induced cell cycle arrest, highlighting their potential antitumor properties.