Positive allosteric modulators of the α7 nicotinic acetylcholine receptor: SAR investigation around PNU-120596

The α7 nicotinic acetylcholine receptor is a calcium permeable, ligand-gated ion channel that modulates synaptic transmission in the hippocampus, thalamus, and cerebral cortex. Previously disclosed work described PNU-120596 that acts as a powerful positive allosteric modulator of the α7 nicotinic acetylcholine receptor. The initial structure-activity relationships around PNU-120596 were gleaned from screening a large thiazole library. Independent systematic examination of the aryl and heteroaryl groups resulted in compounds with enhanced potency and improved physico-chemical properties culminating in the identification of 16 (PHA-758454). In the presence of acetylcholine, 16 enhanced evoked currents in rat hippocampal neurons. In a rat model of impaired sensory gating, treatment with 16 led to a reversal of the gating deficit in a dose-dependent manner. These results demonstrate that aryl heteroaryl ureas, like compound 16, may be useful tools for continued exploration of the unique biology of the α7 nicotinic acetylcholine receptor.

Investigation of aminopyridiopyrazinones as PDE5 inhibitors: Evaluation of modifications to the central ring system

Efforts to improve the potency and physical properties of the aminopyridiopyrazinone class of PDE5 inhibitors through modification of the core ring system are described. Five new ring systems are evaluated and features that impart improved potency and improved solubility are delineated.

Discovery of N-[(3R,5R)-1-azabicyclo[3.2.1]oct-3-yl]furo[2,3-c]pyridine-5-carboxamide as an agonist of the alpha7 nicotinic acetylcholine receptor: in vitro and in vivo activity

A novel alpha7 nAChR agonist, N-[(3R,5R)-1-azabicyclo[3.2.1]oct-3-yl]furo[2,3-c]pyridine-5-carboxamide (3a, PHA-709829), has been identified for the potential treatment of cognitive deficits in schizophrenia. The compound shows potent and selective alpha7 in vitro activity, excellent brain penetration, good rat oral bioavailability and robust in vivo efficacy in a rat auditory sensory gating model.

Design, synthesis, structure–activity relationship, and in vivo activity of azabicyclic aryl amides as α7 nicotinic acetylcholine receptor agonists

A novel set of azabicyclic aryl amides have been identified as potent and selective agonists of the alpha7 nAChR. A two-pronged approach was taken to improve the potential hERG liability of previously disclosed alpha7 nAChR agonist, PNU-282,987, while maintaining the compound's other desirable pharmacological properties. The first approach involved further exploration of the aryl carboxylic acid fragment of PNU-282,987, while the second approach focused on modification of the azabicyclic amine portion of PNU-282,987. The best compounds from each series are characterized by rapid brain penetration, good oral bioavailability in rat, and demonstrate in vivo efficacy in a rat P50 auditory sensory gating assay. At least one analog from each series (1h, 1o, 2a, 9a, and 18a) shows an improved hERG safety profile over PNU-282,987.