ABSTRACT
The toxic hallucinogen 25B-NBOMe is very rapidly degraded by human liver microsomes and has low oral bioavailability. Herein we report on the synthesis, microsomal stability, and 5-HT2A/5-HT2C receptor profile of novel analogues of 25B-NBOMe modified at the primary site of metabolism. Although microsomal stability could be increased while maintaining potent 5-HT2 receptor agonist properties, all analogues had an intrinsic clearance above 1.3 L/kg/h predictive of high first-pass metabolism.
Subject(s)
Phenethylamines/pharmacology , Phenethylamines/pharmacokinetics , Serotonin 5-HT2 Receptor Agonists/pharmacology , Serotonin 5-HT2 Receptor Agonists/pharmacokinetics , Anisoles/chemistry , Cell Line , Drug Evaluation, Preclinical , Drug Stability , HEK293 Cells , Hallucinogens/chemistry , Humans , Microsomes, Liver/drug effects , Microsomes, Liver/metabolism , Phenethylamines/chemical synthesis , Phenethylamines/chemistry , Receptor, Serotonin, 5-HT2A/genetics , Receptor, Serotonin, 5-HT2A/metabolism , Receptor, Serotonin, 5-HT2C/genetics , Receptor, Serotonin, 5-HT2C/metabolism , Serotonin 5-HT2 Receptor Agonists/chemical synthesis , Stereoisomerism , Structure-Activity RelationshipABSTRACT
Screening a library of small-molecule compounds using a cell line expressing human GABA transporter 3 (hGAT3) in a [(3)H]GABA uptake assay identified isatin derivatives as a new class of hGAT3 inhibitors. A subsequent structure-activity relationship (SAR) study led to the identification of hGAT3-selective inhibitors (i.e., compounds 20 and 34) that were superior to the reference hGAT3 inhibitor, (S)-SNAP-5114, in terms of potency (low micromolar IC50 values) and selectivity (>30-fold selective for hGAT3 over hGAT1/hGAT2/hBGT1). Further pharmacological characterization of compound 20 (5-(thiophen-2-yl)indoline-2,3-dione) revealed a noncompetitive mode of inhibition at hGAT3. This suggests that this compound class, which has no structural resemblance to GABA, has a binding site different from the substrate, GABA. This was supported by a molecular modeling study that suggested a unique binding site that matched the observed selectivity, inhibition kinetics, and SAR of the compound series. These compounds are the most potent GAT3 inhibitors reported to date that provide selectivity for GAT3 over other GABA transporter subtypes.
