Angiotensin II receptor antagonists containing a phenylpyridine element

Understanding electrostatic and steric requirements related to hypertensive action of AT(1) antagonists using molecular modeling techniques

AT1 receptor is an interesting biological target involved in several important diseases, such as blood hypertension and cardiovascular pathologies. In this study we investigated the main electrostatic and steric features of a series of AT1 antagonists related to hypertensive activity using structure and ligand-based strategies (docking and CoMFA). The generated 3D model had good internal and external consistency and was used to predict the potency of an external test set. The predicted values of pIC50 are in good agreement with the experimental results of biological activity, indicating that the 3D model can be used to predict the biological property of untested compounds. The electrostatic and steric CoMFA maps showed molecular recognition patterns, which were analyzed with structure-based molecular modeling studies (docking). The most and the least potent compounds docked into the AT1 binding site were subjected to molecular dynamics simulations with the aim to verify the stability and the flexibility of the ligand-receptor interactions. These results provided valuable insights on the electronic/structural requirements to design novel AT1 antagonists.

Further studies on imidazo[4,5-b]pyridine AT1 angiotensin II receptor antagonists. Effects of the transformation of the 4-phenylquinoline backbone into 4-phenylisoquinolinone or 1-phenylindene scaffolds

The 4-phenylquinoline fragment of novel AT(1) receptor antagonists 4 based on imidazo[4,5-b]pyridine moiety was replaced by 4-phenylisoquinolinone (compounds 5) or 1-phenylindene (compounds 6) scaffolds to investigate the structure-activity relationships. Binding studies showed that most of the synthesized compounds display high affinity for the AT(1) receptor. Because of the in vitro high potency of carboxylic acids 5b,f, they were evaluated in permeability (in Caco-2 cells) and in pharmacokinetic studies in comparison with quinoline derivatives 4b,i,j,k. The studies showed that these compounds are characterized by rapid excretion, low membrane permeability, and low oral bioavailability. The structure optimization of the indene derivatives led to compounds 6e,f possessing interesting AT(1) receptor affinities. Optimization produced polymerizing AT(1) receptor ligand 6c, which forms a thermoreversible polymer (poly-6c) and is released from the latter by a temperature-dependent kinetics. The results suggest the possibility of developing novel polymeric prodrugs based on a new release mechanism. Finally, a set of 34 AT(1) receptor antagonists was used as a new test for the evaluation of the predictive capability of the previously published qualitative and quantitative pharmacophore models.

Design, Synthesis, Structural Studies, Biological Evaluation, and Computational Simulations of Novel Potent AT1Angiotensin II Receptor Antagonists Based on the 4-Phenylquinoline Structure

Novel AT(1) receptor antagonists bearing substituted 4-phenylquinoline moieties instead of the classical biphenyl fragment were designed and synthesized as the first step of an investigation devoted to the development of new antihypertensive agents and to the understanding of the molecular basis of their pharmacodynamic and pharmacokinetic properties. The newly synthesized compounds were tested for their potential ability to displace [(125)I]Sar(1),Ile(8)-Ang II specifically bound to AT(1) receptor in rat hepatic membranes. These AT(1) receptor binding studies revealed nanomolar affinity in several of the compounds under study. The most potent ligands 4b,t were found to be equipotent with losartan and possessed either a 3-tetrazolylquinoline or a 2-amino-3-quinolinecarboxylic moiety, respectively. Moreover, some selected compounds were evaluated for antagonism of Ang II-induced contraction in rabbit aortic strips, and the most potent compounds in the binding test 4b,t were slightly more potent than losartan in inhibiting Ang II-induced contraction. Finally, the most relevant structure-affinity relationship data were rationalized by means of computational studies performed on the isolated ligands as well as by computational simulations on the ligands complexed with a theoretical AT(1) receptor model.