5-HT 7 R belongs to a family of G protein-coupled receptors and is associated with a variety of physiological processes in the central nervous system via the activation of the neurotransmitter serotonin (5-HT). To develop selective and biased 5-HT 7 R ligands, we designed and synthesized a series of pyrazolyl-diazepanes 2 and pyrazolyl-piperazines 3, which were evaluated for binding affinities to 5-HTR subtypes and functional selectivity for G protein and β-arrestin signaling pathways of 5-HT 7 R. Among them, 1-(3-(3chlorophenyl)-1H-pyrazol-4-yl)-1,4-diazepane 2c showed the best binding affinity for 5-HT 7 R and selectivity over other 5-HTR subtypes. It was also revealed as a G protein-biased antagonist. The self-grooming behavior test was performed with 2c in vivo with Shank3 −/− transgenic (TG) mice, wherein 2c significantly reduced self-grooming duration time to the level of wild-type mice. The results suggest that 5-HT 7 R could be a potential therapeutic target for treating autism spectrum disorder stereotypy.

There has been significant attention concerning the biased agonism of G protein-coupled receptors (GPCRs), and it has resulted in various pharmacological benefits. 5-HT 7 R belongs to a GPCR, and it is a promising pharmaceutical target for the treatment of neurodevelopmental and neuropsychiatric disorders. Based on our previous research, we synthesized a series of 6-chloro-2′-methoxy biphenyl derivatives 1, 2, and 3 with a variety of amine scaffolds. These compounds were evaluated for their binding affinities to 5-HTR subtypes and their functional selectivity toward the Gs protein and the β-arrestin signaling pathways of 5-HT 7 R. Among them, 2-(6chloro-2′-methoxy-[1,1′-biphenyl]-3-yl)-N-ethylethan-1-amine, 2b, was found to be a G-protein-biased ligand of 5-HT 7 R. In an in vivo study with Shank3 transgenic mice, the self-grooming behavior test was performed with 2b, which increased the duration of selfgrooming. The experiments further suggested that 5-HT 7 R is associated with autism spectrum disorders (ASDs) and could be a therapeutic target for the treatment of stereotypy in ASDs.