GW274150 and GW273629 are potent and highly selective inhibitors of inducible nitric oxide synthase in vitro and in vivo

1 GW274150 ([2-[(1-iminoethyl) amino]ethyl]-L-homocysteine) andGW273629 (3-[[2-[(1-iminoethyl) amino]ethyl]sulphonyl]-L-alanine) are potent, time-dependent,highly selective inhibitors of human inducible nitric oxide synthase (iNOS) vs endothelial NOS (eNOS) (> 100-fold) or neuronal NOS ( nNOS) (> 480-fold). GW274150 and GW273629 are arginine competitive, NADPH-dependent inhibitors of human iNOS with steady state K-d values of <40 and <90 nM, respectively. 2 GW274150 and GW273629 inhibited intracellular iNOS in J774 cells in a time-dependent manner, reaching IC50 values of 0.2 +/- 0.04 and 1.3 +/- 0.16 mu M, respectively. They were also acutely selective in intact rat tissues: GW274150 was >260-fold and 219-fold selective for iNOS against eNOS and nNOS, respectively, while GW273629 was >150-fold and 365-fold selective for iNOS against eNOS and nNOS, respectively. 3 The pharmacokinetic profile of GW274150 was biphasic in healthy rats and mice with a terminal half-life of similar to 6 h. That of GW273629 was also biphasic in rats, producing a terminal half-life of similar to 3 h. In mice however, elimination of GW273629 appeared monophasic and more rapid (similar to 10 min). Both compounds show a high oral bioavailability (>90%) in rats and mice. 4 GW274150 was effective in inhibiting LPS-induced plasma NOx levels in mice with an ED50 of 3.2 +/- 0.7 mg kg(-1) after 14 hintraperitoneally (i.p.) and 3.8 +/- 1.5 mg kg(-1) after 14 h when administered orally. GW273629 showed shorter-lived effects on plasma NOx and an ED50 of 9 +/- 2 mg kg(-1) after 2 h when administered i. p. 5 The effects of GW274150 andGW273629 in vivo were consistent with high selectivity for iNOS, as these inhibitors were of low potency against nNOS in the rat cerebellum and did not cause significant effects on blood pressure in instrumented mice.