5-HT6 Receptor antagonists. I. Screening of the library of various heterocyclic compounds containing an alkylsulfonyl moiety

High-throughput screening of a specific set (focused library) of heterocyclic compounds containing an alkylsulfonyl moiety (a total of 2827 compounds from 78 combinatorial libraries) was performed in order to discover highly effective 5-HT6 receptor antagonists. The screening identified several compounds that exhibited pronounced inhibiting properties for 5-HT6 receptors that enabled them to be used to develop new highly effective drugs for treating central nervous system disturbances. The structures of most antagonists corresponded to the PhM2 pharmacophore model, which confirmed its potential in the search for effective 5-HT6 receptor antagonists. It was established that the structure of the substituent introduced in the vicinity of the sulfonyl moiety in the PhM2 ligands could affect their pharmacological activity, including the ability to block serotonin-induced 5-HT6 receptor-mediated cell responses. In particular, bulky electron-donating substituents decreased the activity whereas a methylamino group increased statistically significantly the 5-HT6 antagonistic activity. Based on these findings, a new pharmacophore model for 5-HT6 antagonists, PhM3, was proposed. It was shown that compounds from the combinatorial libraries with a sulfonyl moiety separated from the heterocyclic and/or aromatic moiety by one (or more) methylenes and heterocyclic compounds containing an alkylsulfonyl moiety or endocyclic sulfonyl, (5-aryl-sulfonyl-3H-[1,2,3]triazol-4-yl)amines, and azoles substituted simultaneously by arylsulfonyl and alkylsulfonyl moieties all had low hit rates and were not promising for discovery of new 5-HT6 receptor antagonists.