Design, synthesis and pharmacological evaluation of novel polycyclic heteroarene ethers as PDE10A inhibitors: Part I.

We report analogue-based rational design and synthesis of two novel series of polycyclic heteroarenes, pyrrolo[3,2-b]quinolines and pyrido[2,3-b]indoles, tethered to a biaryl system by a methyl-, ethyl- or propyl ether as PDE10A inhibitors. A number of analogues were prepared with variable chain length and evaluated for their ability to block PDE10A enzyme using a radiometric assay. Detailed SAR analyses revealed that compounds with an ethyl ether linker are superior in potency compared to compounds with methyl or propyl ether linkers. These compounds, in general, showed poor metabolic stability in rat and human liver microsomes. The metabolic profile of one of the potent compounds was studied in detail to identify metabolic liabilities of these compounds. Structural modifications were carried out that resulted in improved metabolic stability without significant loss of potency.

Design, synthesis and pharmacological evaluation of novel polycyclic heteroarene ethers as PDE10A inhibitors: part II.

We report the design and synthesis of novel pyrrolo[3,2-b]quinoline containing heteroarene ethers as PDE10A inhibitors with good to excellent potency, selectivity and metabolic stability. Further optimization of this primary series resulted in the identification of 1-methyl-3-(4-{[3-(pyridine-4-yl)pyrazin-2-yl]oxy}phenyl)-1H-pyrrolo[3,2-b]pyridine 13a with good hPDE10A potency (IC50: 6.3 nM), excellent selectivity over other related PDEs and desirable physicochemical properties. The compound exhibited high peripheral and adequate brain levels upon oral dosing in rodents. The compound also showed excellent efficacy in multiple preclinical animal models related to psychiatric disorders, particularly schizophrenia.