SAR study of bicyclo[4.1.0]heptanes as melanin-concentrating hormone receptor R1 antagonists: Taming hERG

Identification of a new small molecule chemotype of Melanin Concentrating Hormone Receptor-1 antagonists using pharmacophore-based virtual screening

MCH receptor is a G protein-coupled receptor with two subtypes R1 and R2. Many studies have demonstrated the role of MCH-R1 in feeding and energy homeostasis. It has been proven that oral administration of small molecule MCH-R1 antagonists significantly reduces food intake and causes a dose-dependent weight loss. In this study, two ligand-based pharmacophores were developed and validated based on recently published MCH-R1 antagonists with diverse structures. Successful pharmacophores had one hydrogen bond acceptor, one positive ionizable, one ring aromatic and two or three hydrophobic groups. These 3D-QSAR models were used for virtual screening of the ZINC chemical database resulting in the identification of nine compounds with more than 50% displacement of radiolabeled MCH at a 20 μM concentration. Moreover, four of these compounds showed antagonistic activities in Aequorin functional assay, including MH-3 which is the first MCH-R1 antagonist based on a diazaspiro[4.5]decane scaffold. The most active compounds were also docked into our previously published MCH-R1 homology model to gain insights into their binding determinants. These compounds could represent a viable starting scaffold for the design of potent MCH-R1 antagonists with improved pharmacokinetic properties as an effective treatment for obesity.

Design of Phthalazinone Amide Histamine H1 Receptor Antagonists for Use in Rhinitis

The synthesis of potent amide-containing phthalazinone H₁ histamine receptor antagonists is described. Three analogues 3e, 3g, and 9g were equipotent with azelastine and were longer-acting in vitro. Amide 3g had low oral bioavailability, low brain-penetration, high metabolic clearance, and long duration of action in vivo, and it was suitable for once-daily dosing intranasally, with a predicted dose for humans of approximately 0.5 mg per day.

Exploring chemical substructures essential for HERG k(+) channel blockade by synthesis and biological evaluation of dofetilide analogues

In this study we followed a new approach to analyze molecular substructures required for hERG channel blockade. We designed and synthesized 40 analogues of dofetilide (1), a potent hERG potassium channel blocker, and established structure-activity relationships (SAR) for their interaction with this important cardiotoxicity-related off-target. Structural modifications to dofetilide were made by diversifying the substituents on the phenyl rings and the protonated nitrogen and by varying the carbon chain length. The analogues were evaluated in a radioligand binding assay and SAR data were derived with the aim to specify structural features that give rise to hERG toxicity.

Synthesis of novel bicyclo[4.1.0]heptane and bicyclo[3.1.0]hexane derivatives as melanin-concentrating hormone receptor R1 antagonists

To address the hERG liability of MCHR1 antagonists such as 1 and 2, new analogs such as 4 and 5 that incorporated a polar heteroaryl group were designed and synthesized. Biological evaluation confirmed that these new analogs retained MCH R1 activity with greatly attenuated hERG liabilities as indicated in the Rb efflux assay.