Robert Lewis Vogel

1,2,5-Thiadiazole derivatives are potent and selective ligands at human 5-HT1A receptors

Amino acid derivatives of 1,2,5-thiadiazol-3-yl-piperazine related to (+)-WAY-100135 and WAY-100635 are potent 5-HT1A receptor agonists and antagonists, which have selective affinity for 5-HT1A receptors versus alpha1 and dopamine (D2, D3, and D4) receptors.

WAY-131256 is an orally active, efficacious, and in vivo functionally selective M1 agonist

Computer modeling of carbachol docked in the human m1 receptor binding pocket has been used to discover a series of carbamate and thiocarbamate chiral, conformationally restricted analogues of carbachol based on azabicyclo[2.2.1]heptan‐3‐ol. These molecules have been evaluated for affinity and efficacy at human muscarinic receptors (m1–m5) transfected into a CHO cell line. None of these compounds was selective in binding. Thiocarbamate analogues had greater affinity for the m1 receptor subtype, but lower efficacy based on comparison of their ability to induce phosphoinositide (PI) turnover. Carbamate analogues had lower affinity for m1 receptors than thiocarbamates and varied in efficacy from 10% to 100% of the carbachol response in phosphoinositide (PI) turnover. One of these analogues 3S,4R‐azabicyclo[2.2.1]heptan‐3‐methylcarbamate, WAY‐131256, (VI) has been characterized as an m1/m2 agonist in vitro. (VI) was equi‐efficacious to the standard m1 agonist, xanomeline (Phase III) in vivo in a scopolamine‐impaired radial arm maze paradigm (MED 1 mg/kg, 5.88 mmol/kg for VI and MED 1 mg/kg, 3.55 mmoles/kg for xanomeline) and was approximately equal to xanomeline in an AF64A‐impaired radial arm maze paradigm. Despite its lack of m1 selectivity in vitro, in vivo experiments on (VI) indicated no significant effect on blood pressure or heart rate at 10 mg/kg (58.78 mmol/kg) (i.p.), and no peripheral side effects attributed to stimulation of either the m2 or m3 receptors (salivation, lacrimation, and chromodacryorrhea) up to doses of 30 mg/kg, 176.2 mmol/kg. These results may be explained by different receptor densities in various brain regions not accounted for in a transfected cell line or by metabolism of (VI) to a m1 selective agonist in vivo. Drug Dev. Res. 40:185–192, 1997.