3,5-Disubstituted indole derivatives as selective human neuronal nitric oxide synthase (nNOS) inhibitors

A series of 3,5-disubstituted indole derivatives was designed, synthesized and evaluated as inhibitors of human nitric oxide synthase (NOS). Various guanidine isosteric groups were explored at the 5-position of the indole ring, while keeping the basic amine side chain such as N-methylpiperidine ring, fixed at the 3-position of the indole ring. Compounds having 2-thiophene amidine and 2-furanyl amidine groups (7, 8, 10 and 12) showed increased activity for human neuronal NOS and good selectivity over endothelial and inducible NOS isoforms. Compound 8 was shown to reverse (10 mg/kg, ip) thermal hyperalgesia in the L ₅/L ₆ spinal nerve ligation (neuropathic pain) model and was devoid of any significant drug-drug interaction potential due to cytochrome P450 inhibition or cardiovascular liabilities associated with the inhibition of endothelial NOS.