New V1a receptor antagonist. Part 2. Identification and optimization of triazolobenzazepines

Discovery and Characterization of RGH-122, a Potent, Selective, and Orally Bioavailable V1a Receptor Antagonist

The V1a receptor is a major contributor in mediating the social and emotional effects of arginine-vasopressin (AVP); therefore it represents a promising target in the treatment of several neuropsychiatric conditions. The aim of this research was to design and synthesize novel and selective V1a antagonists with improved in vitro and in vivo profiles. Through optimization and detailed SAR studies, we developed low nanomolar antagonists, and further characterizations led to the discovery of the clinical candidate compound 43 (RGH-122). The CNS activity of the compound was determined in a 3-chamber social preference test of autism in which RGH-122 successfully enhanced social preference with the lowest effective dose of 1.5 mg/kg.

Synthesis and Characterization of New V1A Antagonist Compounds: The Separation of Four Atropisomeric Stereoisomers

A new class of selective vasopressin receptor 1A (V_1A) antagonists was identified, where "methyl-scan" was performed around the benzene ring of the 5-hydroxy-triazolobenzazepine core. This led to the synthesis of two 10-methyl derivatives, each possessing a chiral axis and a stereogenic center. The four atropisomeric stereoisomers (involving two enantiomer pairs and atropisomeric diastereomers) could be successfully isolated and spectroscopically characterized. According to the in vitro pharmacological profiles of the compounds, the human V_1A receptor has a strong preference toward the isomers having an aR axial chirality, the most active isomer being the aR,5S isomer. Furthermore, the structure-activity relationships obtained for the isomers and for the newly synthesized analogues could be tentatively explained by an in silico study.

Discovery of New Heterocyclic Ring Systems as Novel and Potent V1A Receptor Antagonists

Autism spectrum disorder is a neurodevelopmental disease with increasing occurrence. Recent studies focus on the development of novel V_1A receptor antagonists which can influence the core symptoms of autism through the AVP pathway. In this study, we describe the synthesis of new heterocyclic ring systems. These are a novel class of brain-penetrating V_1A antagonists with improved metabolic stability and in vivo potency. The efficacy of the compounds was strongly influenced by the position of the chlorine atom, suggesting halogen bond formation between the ligands and the V_1A receptor.