Design, Synthesis, and Structure-Activity Relationship Studies of Novel Indolyalkylpiperazine Derivatives as Selective 5-HT1A Receptor Agonists.

5-HT1A receptor (5-HT1AR) agonists have been implicated in the treatment of a variety of central nervous system (CNS) diseases such as depression and anxiety, et al. Based on our previously found compound FW01 (Ki = 51 ± 16 nM) obtained by virtual screening, a series of FW01 derivatives were designed and synthesized by the modification of the amide tail group as well as indole headgroup of FW01. SAR exploration found that amide tail group and indole headgroup play pivotal roles in determining the binding affinity and selectivity on dopamine and serotonin receptor subtypes. Among all tested compounds, 9_24 has a Ki value of 5 ± 0.6 nM with a good selectivity toward 5-HT1AR. The [35S] GTPγS assay showed that 9_24 is a full agonist toward 5-HT1AR with an EC50 value of 0.059 nM, which shows 266.2 and 146.4-fold selectivity to 5-HT2A and D3 respectively. Molecular dynamics simulations and molecular docking studies with 5-HT1AR-9_24 were performed to disclose the mechanism of its high activity and selectivity. Finally, a detailed stepwise 9_24 induced signal transduction mechanism of 5-HT1AR is proposed.