Contact PD/PI: Ablordeppey, Seth Funded Project Summary/Abstract: Numerous studies have indicated that 5-HT7R plays a significant role in various psychophysiological functions such as mood stability, cognitive and motor functions, pain tolerance, sleep patterns, appetite, and thermoregulation. Pre-clinical findings have established the role of 5-HT7R in autism spectrum disorders, Fragile X syndrome (FXS), epilepsy, sleep disorders, neuropathic pain and migraine. Meanwhile, several 5-HT7R agonists, have been reported and their potential use in various CNS conditions are being investigated. However, the beneficial effects of activation or blockade of the 5-HT7R is not often clearly established, primarily due to the lack of selective 5-HT7R agents. Even more critical is the absence of biased ligands that could clarify several controversial observations that relate to the 5-HT7R. Thus, our goal to design, synthesize and pharmacologically evaluate new agents with biased signaling towards G-Protein or β- arrestin signaling pathways hold great promise in understanding the 5-HT7R and its application to the treatment of various CNS disorders. Three specific aims (SAs) are proposed. SA 1 will focus on extending our studies on the lead agents for their drug-like properties including brain penetration, pharmacokinetic, metabolic, and bioavailability assessments and cardiotoxicity predictions (HERG, 5- HT2BR). Based on the metabolic evaluations of lead compound 55933, the synthesis and screening of new compounds is proposed in SA 2. This specific aim will also focus on optimization and design of new agents to address the metabolic stability issues such as aromatization and glucuronidation observed in the preliminary studies. For this reason, aromatization susceptible tetrahydroisoquinoline moiety will be replaced with isoindoline which could not undergo aromatization and the CH2OH group will be replaced with substituents such as -F, -CONH2 to restrict glucuronidation. In addition, exploring the electron donating/ withdrawing (σ values) and hydrophilic/hydrophobic (pi values) space around the THI/isoindoline ring systems with bioisosteric substituents, will reveal any improvements in their drug-like characteristics. Simultaneously, docking studies will be carried out using homology models to identify interactions with the key amino acid residues involved in inducing conformations associated with β-arrestin recruitment to the 5-HT7R. SA 3 will cover functional selectivity studies of lead 5-HT7R ligands for their agonist/antagonist properties and G-Protein or β- arrestin signaling bias followed by evaluation of their effect on sleep architecture and NREM/REM sleep pattern under in vivo conditions. Finally, selected test compounds will be compared with SB269970 (5-HT7R antagonist) and compound 1g, a 5-HT7R partial agonist (as a positive control) for their effect on NREM/REM sleep pattern in a mouse model. Progress Report Summary of Parent Award: The full progress...