Halogen Bonding Hot Spots as a Constraint in Virtual Screening: A Case Study of 5-HT₇R

The recently developed and used molecular modeling approach to search for privileged amino acids for halogen bonding (XB hot spots) through XSAR sets has been applied to 5-HT₇R. Herein, among all identified 5-HT₇R XB hot spots, the S5x42 was employed in a virtual screening protocol as a constraint. Through a designed virtual screening protocol, 63 XSAR sets (156 compounds) were selected from more than 8 million commercially available compounds and examined using in vitro assay toward 5-HT₇R. A 68% accuracy was found in predicting halogenated derivatives with higher affinity for 5-HT₇R than their unsubstituted analogs. Moreover, it was observed that a halogen bond formed between S5x42 and a chlorine atom at the 3-position of the arylpiperazine fragment caused the most remarkable, 35.4-fold increase in binding affinity for 5-HT₇R when compared to the nonhalogenated analog. Interestingly, molecular dynamics simulations showed the formation of a bifurcated halogen bond with S5x42.