Synthesis and biological activity of novel potent endothelin-converting enzyme-1 inhibitors.

Through directed screening of metalloprotease inhibitors, CGS 30084 (1) has been identified as a potent endothelin-converting enzyme-1 (ECE-1) inhibitor in vitro (IC50 = 77 nM). Herein we report the syntheses and biological activities of analogues derived from this lead, based on modifications of the biphenyl moiety. Compound 10, the thioacetate methyl ester prodrug derivative of compound 6m, was found to be an orally active and potent inhibitor of ECE-1 activity in rats.

Design and synthesis of a potent and selective endothelin-converting enzyme inhibitor, CGS 35066.

CGS 26303 has previously been shown to inhibit human endothelin converting enzyme-1 (ECE-1) with an IC50 of 410 nM and to be efficacious in several animal disease models. However, it is a more potent inhibitor of neutral endopeptidase 24.11 (NEP) with an IC50 of 1 nM. The aim of this study was to optimize CGS 26303 for greater potency and selectivity towards ECE-1 inhibition. The in vivo activity of the compounds was assessed by inhibition of the big endothelin-1 (ET-1)-induced pressor response in anesthetized rats at 90 min after treatment with a dose of 10 mg/kg, i.v. Under these conditions, CGS 26303 inhibited the pressor response to big ET-1 by 50%. Replacement of the biphenyl and tetrazol groups in CGS 26303 with a dibenzofuran and carboxylic acid, respectively, yielded CGS 35066, a potent ECE-1 inhibitor having an IC50 of 22 nM. In contrast, these substitutions markedly weakened the NEP inhibitory activity of the compound to an IC50 of 2.3 microM. CGS 35066 also exhibited a potent and sustained ECE-1 inhibitory activity in vivo, blocking the pressor response to big ET-1 by 84%. Its orally active prodrug, CGS 35339, was obtained by introducing two phenyl groups at the phosphonic acid substituent in CGS 35066. Therefore, CGS 35066 and CGS 35339 represent novel compounds for assessing the pathogenic role of ET-1 overproduction in various disease states.

Pharmacological properties of CGS 35066, a potent and selective endothelin-converting enzyme inhibitor, in conscious rats.

The purpose of this study was to examine the pharmacologic properties of CGS 35066, a novel aminophosphonate inhibitor of endothelin-converting enzyme-1 (ECE-1). CGS 35066 inhibited the activity of human ECE-1 and rat kidney neutral endopeptidase 24.11 (NEP) in vitro with IC50 values of 22 +/- 0.9 nM and 2.3 +/- 0.03 microM, respectively. The in vivo effects of CGS 35066 were characterized in conscious, catheterized rats. At 30 and 120 min after treatment with vehicle, big endothelin-1 (big ET-1, 0.3 nmol/kg i.v.) produced increases in mean arterial pressure (MAP) of 982 +/- 31 and 992 +/- 43 mmHg x min (area under the curve), respectively. Doses of 0.3, 1.0, 3.0 and 10.0 mg/kg i.v., of CGS 35066 blocked these pressor responses by 61 +/- 7, 78 +/- 4, 93 +/- 4 and 98 +/- 2% at 30 min (p < 0.05 compared with vehicle controls, all doses), and by 29 +/- 7, 63 +/- 5, 63 +/- 5 and 84 +/- 10% at 120 min (p < 0.05, all doses). In contrast, the pressor effect (58 +/- 6 mmHg) of angiotensin-I (300 ng/kg i.v.) was unaffected by the ECE-1 inhibitor (10 mg/kg i.v.) indicating the absence of activity against angiotensin-converting enzyme. In rats infused with atrial natriuretic peptide (ANP), CGS 35066, at 1 mg/kg, had no effect on plasma irANP; however, irANP levels were doubled at a dose of 30 mg/kg. These results demonstrate that CGS 35066 is the most potent and selective ECE inhibitor identified to date.

CGS 34043: a non-peptidic, potent and long-acting dual inhibitor of endothelin converting enzyme-1 and neutral endopeptidase 24.11.

Endothelin-1 (ET- 1) is a potent vasoconstrictor. Its biosynthesis is catalyzed by endothelin converting enzyme (ECE). In contrast, atrial natriuretic peptide (ANP) is a potent vasorelaxant and diuretic, and it is mainly degraded by neutral endopeptidase 24.11 (NEP). Therefore, compounds that can suppress the production of ET-1 by inhibiting ECE while simultaneously potentiating the levels of ANP by inhibiting NEP may be novel agents for the treatment of cardiovascular and renal dysfunction. CGS 34043 is one such compound, which inhibited the activities of ECE-1a and NEP with IC50 values of 5.8 and 110 nM, respectively. In vivo, it inhibited the pressor response induced by big ET-1, the precursor of ET-1, dose-dependently in rats, and the inhibition was sustained for at least 2 hr. In addition, CGS 34043 increased plasma ANP by 150% up to 4 hr after an intravenous dose of 10 mg/kg in conscious rats infused with ANP. However, this compound had no effect on the angiotensin I-induced pressor response. These results demonstrate that CGS 34043 is a potent and long-lasting dual inhibitor of ECE-1 and NEP. Consequently, it may be beneficial for the treatment of diseases in which an overproduction of ET-1 and/or enhanced degradation of ANP plays a pathogenic role. The activity of CGS 34753, an orally active prodrug of CGS 34043, is also described.

Characterization of a potent and selective endothelin-B receptor antagonist, IRL 2500.

IRL 2500 [N-(3,5-dimethylbenzoyl)-N-methyl-(D)-(4-phenylphenyl)-alany l-L- tryptophan] inhibited the binding of [125I]-endothelin-1 (ET-1) to human ETB (IC50 1.3 +/- 0.2 nM) and ETA (IC50 94 +/- 3 nM) receptors expressed in transfected Chinese hamster ovary (CHO) cells. In in vitro studies, IRL 2500 inhibited the sarafotoxin S6c (STX6c)-mediated contraction of the dog saphenous vein (pKb 7.77) and the STX6c-induced relaxation of the preconstricted rabbit mesenteric artery (pKb 6.92). In the anesthetized rat, IRL 2500 (10 mg/kg, i.v.) inhibited the initial transient decrease in mean arterial pressure (MAP) induced by the ETB-selective agonist IRL 1620 (0.5 nmol/kg, i.v.). IRL 2500 also attenuated the IRL 1620-mediated increase in renal vascular resistance (RVR) in the anesthetized rat. Therefore, IRL 2500 is a potent and selective ETB receptor antagonist that can be used to delineate ET responses mediated by the ETB receptor.