A Tetrahydrobiopterin-Displacing Potent Neuronal Nitric Oxide Synthase Inhibitor with an Unprecedented Binding Mode.
Weerawarna, P.M., Li, H., Rathnayake, A.D., Hardy, C.D., Poulos, T.L., Silverman, R.B.(2025) ACS Med Chem Lett 16: 651-659
- PubMed: 40236557 
- DOI: https://doi.org/10.1021/acsmedchemlett.5c00062
- Primary Citation of Related Structures:  
9C1Y, 9C1Z - PubMed Abstract: 
Nitric oxide synthase (NOS) is a pivotal enzyme that regulates various physiological processes, and the dysregulation of neuronal NOS (nNOS) is implicated in neurodegenerative diseases. In our efforts to leverage existing X-ray crystallography data to develop novel aminoquinoline-pyridine hybrid inhibitors and evaluate their inhibitory activities and interactions with NOS isoforms, we identified compounds 8 and 9 as potent human nNOS inhibitors ( K i = 38 and 22 nM, respectively). Notably, compound 8 displayed an unprecedented binding mode, displacing the essential cofactor tetrahydrobiopterin (H 4 B). Furthermore, compound 9 exhibited excellent selectivity, with a 900-fold preference for human nNOS over human eNOS, making it one of the most potent and selective aminoquinoline-based nNOS inhibitors reported to date. Herein we present our inhibitor design rationale, the synthesis, and the biochemical/physical evaluation of binding along with X-ray crystallographic studies with three NOS isoforms, providing detailed insights into the observed potency and selectivity of these inhibitors.
Organizational Affiliation: 
Departments of Chemistry and Molecular Biosciences, Chemistry of Life Processes Institute, and Center for Developmental Therapeutics, Northwestern University, Evanston, Illinois 60208, United States.