BACKGROUND AND PURPOSE Despite growing evidence that inhibition of α6β2‐containing (α6β2*) nicotinic acetylcholine receptors (nAChRs) may be beneficial for the therapy of tobacco addiction, the lack of good sources of α6β2*‐nAChRs has delayed the discovery of α6β2‐selective antagonists. Our aim was to generate a cell line stably expressing functional nAChRs with α6β2 properties, to enable pharmacological characterization and the identification of novel α6β2‐selective antagonists. EXPERIMENTAL APPROACH Different combinations of the α6, β2, β3, chimeric α6/3 and mutant β3V273S subunits were transfected in human embryonic kidney cells and tested for activity in a fluorescent imaging plate reader assay. The pharmacology of rat immune‐immobilized α6β2*‐nAChRs was determined with 125I‐epibatidine binding. KEY RESULTS Functional channels were detected after co‐transfection of α6/3, β2 and β3V273S subunits, while all other subunit combinations failed to produce agonist‐induced responses. Stably expressed α6/3β2β3V273S‐nAChR pharmacology was unique, and clearly distinct from α4β2‐, α3β4‐, α7‐ and α1β1δε‐nAChRs. Antagonist potencies in inhibiting α6/3β2β3V273S‐nAChRs was similar to their binding affinity for rat native α6β2*‐nAChRs. Agonist affinities for α6β2*‐nAChRs was higher than their potency in activating α6/3β2β3V273S‐nAChRs, but their relative activities were equivalent. Focussed set screening at α6/3β2β3V273S‐nAChRs, followed by cross‐screening with the other nAChRs, led to the identification of novel α6β2‐selective antagonists. CONCLUSIONS AND IMPLICATIONS We generated a mammalian cell line stably expressing nAChRs, with pharmacological properties similar to native α6β2*‐nAChRs, and used it to identify novel non‐peptide, low molecular weight, α6β2‐selective antagonists. We also propose a pharmacophore model of α6β2 antagonists, which offers a starting point for the development of new smoking cessation agents.

A novel series of 1,2,4-triazol-3-yl-azabicyclo[3.1.0]hexanes with high affinity and selectivity for the DA D(3) receptor and excellent pharmacokinetic profiles was recently reported. We also recently discussed the role of the linker associated with the triazole moiety. In this manuscript, we are reporting a detailed exploration of the region of the receptor interacting with the amine terminus of the scaffold wherein SAR and developability data associated with these novel templates was undertaken.

A pharmacophore model for triple reuptake inhibitors and the new class of 1-(aryl)-6-[alkoxyalkyl]-3-azabicyclo[3.1.0]hexanes were recently reported. Further investigation in this area led to the identification of a new series of potent and selective triple reuptake inhibitors endowed with good developability characteristics. Excellent bioavailability and brain penetration are associated with this series of 6-(3,4-dichlorophenyl)-1-[(methyloxy)methyl]-3-azabicyclo[4.1.0]heptanes together with high in vitro potency and selectivity at SERT, NET, and DAT. In vivo microdialysis experiments in different animal models and receptor occupancy studies in rat confirmed that derivative 17 showed an appropriate profile to guarantee further progression of the compound.

The discovery of new highly potent and selective triple reuptake inhibitors is reported. The new classes of 1-(aryl)-6-[alkoxyalkyl]-3-azabicyclo[3.1.0]hexanes and 6-(aryl)-6-[alkoxyalkyl]-3-azabicyclo[3.1.0]hexanes are described together with detailed SAR. Appropriate decoration of the scaffolds was achieved with the help of a triple reuptake inhibitor pharmacophore model detailed here. Selected derivatives showed good oral bioavailability (>30%) and brain penetration (B/B > 4) in rats associated with high in vitro potency and selectivity at SERT, NET, and DAT. Among these compounds, microdialysis and in vivo experiments confirm that derivative 15 has an appropriate developability profile to be considered for further progression.

Bioisoteric replacement of the metabolically labile N-methyl amide group of a series of benzoxazinones with small heterocyclic rings has led to novel series of fused tricyclic benzoxazines which are potent 5-HT(1A/B/D) receptor antagonists with and without concomitant human serotonin transporter (hSerT) activity. Optimizing against multiple parameters in parallel identified 6-{2-[4-(2-methyl-5-quinolinyl)-1-piperazinyl]ethyl}-4H-imidazo[5,1-c][1,4]benzoxazine-3-carboxamide (GSK588045) as a potent 5-HT(1A/B/D) receptor antagonist with a high degree of selectivity over human ether-a-go-go related gene (hERG) potassium channels, favorable pharmacokinetics, and excellent activity in vivo in rodent pharmacodynamic (PD) models. On the basis of its outstanding overall profile, this compound was progressed as a clinical candidate with the ultimate aim to assess its potential as a faster acting antidepressant/anxiolytic with reduced side-effect burden.

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