1400W dihydrochloride is a potent and selective inhibitor of human inducible NO synthase with K_i values of 7 nM. IC50 & Target: Ki: 7 nM (iNOS), 2 µM (nNOS), 50 µM (eNOS)^[1] In Vitro: 1400W is a slow, tight binding inhibitor of human inducible nitric- oxide synthase (iNOS). The slow onset of inhibition by 1400W shows saturation kinetics with a maximal rate constant of 0.028 s^-1 and a binding constant of 2.0 μM. Inhibition is dependent on the cofactor NADPH. 1400W is at least 5000-fold selective for iNOS versus eNOS. In contrast, inhibition of human neuronal NOS and endothelial NOS (eNOS) is relatively weaker, rapidly reversible, and competitive with L-arginine, with K_i values of 2 μM and 50 μM, respectively^[1]. 1400W treatment inhibits iNOS expression without affecting nNOS or eNOS. 1400W also reduces NO, 3-NT and MDA production, and prevents neuronal cell apoptosis in cerebral cortex^[2]. In Vivo: 1400W potently (ED₅₀=0.3 mg/kg) reduces the delayed vascular injury in rats attributable to LPS-induced iNOS but fails to exacerbate acute vascular leakage when given concurrently with LPS^[1]. Administration of 1400W lowers NOx levels in all the experimental groups. In addition, lipid peroxidation, the percentage of apoptotic cells, and nitrated protein expression fall in the late post-hypoxia period (48 h and 5 days)^[3].