Discovery of N-[5-(6-Chloro-3-cyano-1-methyl-1H-indol-2-yl)-pyridin-3-ylmethyl]-ethanesulfonamide, a Cortisol-Sparing CYP11B2 Inhibitor that Lowers Aldosterone in Human Subjects.

Human clinical studies conducted with LCI699 established aldosterone synthase (CYP11B2) inhibition as a promising novel mechanism to lower arterial blood pressure. However, LCI699's low CYP11B1/CYP11B2 selectivity resulted in blunting of adrenocorticotropic hormone-stimulated cortisol secretion. This property of LCI699 prompted its development in Cushing's disease, but limited more extensive clinical studies in hypertensive populations, and provided an impetus for the search for cortisol-sparing CYP11B2 inhibitors. This paper summarizes the discovery, pharmacokinetics, and pharmacodynamic data in preclinical species and human subjects of the selective CYP11B2 inhibitor 8.

Structure-Activity Relationships, Pharmacokinetics, and in Vivo Activity of CYP11B2 and CYP11B1 Inhibitors.

CYP11B2, the aldosterone synthase, and CYP11B1, the cortisol synthase, are two highly homologous enzymes implicated in a range of cardiovascular and metabolic diseases. We have previously reported the discovery of LCI699, a dual CYP11B2 and CYP11B1 inhibitor that has provided clinical validation for the lowering of plasma aldosterone as a viable approach to modulate blood pressure in humans, as well normalization of urinary cortisol in Cushing's disease patients. We now report novel series of aldosterone synthase inhibitors with single-digit nanomolar cellular potency and excellent physicochemical properties. Structure-activity relationships and optimization of their oral bioavailability are presented. An illustration of the impact of the age of preclinical models on pharmacokinetic properties is also highlighted. Similar biochemical potency was generally observed against CYP11B2 and CYP11B1, although emerging structure-selectivity relationships were noted leading to more CYP11B1-selective analogs.

CGS 35601 and its orally active prodrug CGS 37808 as triple inhibitors of endothelin-converting enzyme-1, neutral endopeptidase 24.11, and angiotensin-converting enzyme.

CGS 35601 is a potent triple inhibitor of endothelin-converting enzyme-1, neutral endopeptidase 24.11, and angiotensin-converting enzyme. It inhibited the activities of these three enzymes with IC50 values of 55, 2 and 22 nM, respectively. In conscious rats, CGS 35601 suppressed the big endothelin-1-induced pressor response by 82% and 72% at 30 and 120 minutes, respectively, following injection at a dose of 10 mg/kg, intravenously. At the same dose, CGS 35601 increased plasma atrial natriuretic peptide (ANP) immunoreactivity by 170% for up to 4 hours in conscious rats infused with ANP, and it inhibited the angiotensin I-induced pressor response by 74-94% within the first 2 hours after dosing. Similar in vivo activities were also observed with its orally active prodrug, CGS 37808. This compound blocked the big endothelin-1- induced pressor response by 71% and 67% at 30 and 120 minutes, respectively, after an oral dose of 10 mgEq/kg in conscious rats. It also increased plasma ANP immunoreactivity by 103% for up to 4 hours and inhibited the angiotensin I-induced pressor response by an average of 49% within the first 4 hours after the same dosing regimen. By suppressing the biosyntheses of endothelin-1 and angiotensin II, two potent vasoconstrictors, while simultaneously potentiating the circulating levels of ANP, a vasorelaxant and diuretic, CGS 35601 and CGS 37808 may represent novel agents for the treatment of cardiovascular and renal diseases.

Synthesis and biological activity of potent heterocyclic thiol-based inhibitors of endothelin-converting enzyme-1.

Directed screening of metalloprotease inhibitors identified CGS 30084 (1) as a potent inhibitor of endothelin-converting enzyme-1 (ECE-1) in vitro (IC(50)=77 nM). Herein we report the syntheses and biological activities of analogues containing modified biphenyl moieties, bearing heterocyclic proximal rings. Compound 20, the thioacetate ethyl ester prodrug derivative of compound 19a, was found to be an orally active and potent inhibitor of ECE-1 activity in rats.

CGS 34226, a thiol-based dual inhibitor of endothelin converting enzyme-1 and neutral endopeptidase 24.11.

Endothelins (ETs) are potent vasoconstrictors and have been implicated in the pathogenesis of various cardiovascular and renal diseases. In contrast, atrial natriuretic peptide (ANP) is a potent vasorelaxant and diuretic agent, which is mainly degraded by neutral endopeptidase 24.11 (NEP) in vivo. Thus, compounds that can suppress the biosynthesis of ETs by inhibiting endothelin converting enzymes (ECEs), which catalyse the final step of post-translational processing of the vasoconstrictors, while simultaneously potentiating the levels of ANP by inhibiting NEP may have novel therapeutic utility. Through targeted screening of our compound library and subsequent optimization, CGS 34226 was identified as a potent, dual inhibitor of ECE-1 and NEP, inhibiting the enzymes with respective IC(50) values of 11 and 4.6 nM. In vivo, CGS 34226 suppressed the big endothelin-1 (big ET-1)-induced pressor response dose-dependently. At 15 and 90 min after an intravenous dose of 30 mg/kg in anaesthetized rats, this compound inhibited the big ET-1-induced effect by 79% and 65% respectively. In addition, CGS 34226 increased plasma ANP immunoreactivity by 120% up to 4 h after an intravenous dose of 10 mg/kg in conscious rats infused with ANP at a rate of 450 ng/kg per min, intravenously. These results show that CGS 34226 is a potent dual inhibitor of ECE-1 and NEP in vitro and in vivo and that the compound may represent a novel agent for the treatment of cardiovascular and renal dysfunction.

Effects of the ECE/NEP inhibitor CGS 34225 on the big ET-1-induced pressor response and plasma atrial natriuretic peptide concentration in conscious rats.

CGS 34226 is a thiol-containing, potent dual inhibitor of endothelin converting enzyme-1 (ECE-1) and neutral endopeptidase 24.11 (NEP) with IC(50) values of 11 and 5 nM respectively. The purpose of the present study was to characterize the inhibitory effects of CGS 34225, an orally active prodrug of CGS 34226, on ECE-1 and NEP in vivo. The effects on ECE-1 and NEP were assessed by determining the inhibition of big endothelin-1 (big ET-1)-induced increases in mean arterial pressure (MAP) and increases in plasma atrial natriuretic peptide (ANP) concentrations respectively, in conscious rats. Thirty and 120 min after the administration of vehicle, big ET-1 (0.3 nmol/kg, intravenously; i.v.) produced pressor responses of approximately 800 mmHg.min (area under the curve for change in MAPxtime). Treatment with CGS 34225 at 1 mgEq/kg, per os (p.o.), decreased the pressor effect of big ET-1 by 39 and 53% at 30 and 120 min respectively (P<0.05, both times). Increasing the dose of CGS 34255 to 30 mgEq/kg, p.o., resulted in greater inhibition, 84 and 92% (P<0.05) at 30 and 120 min respectively. Furthermore, at this higher dose, the inhibitory effect on ECE-1 was long-lasting, averaging 86, 75 and 30% (P<0.05, all times) at 4, 8 and 24 h respectively. In rats treated with vehicle, the infusion of ANP at 450 ng/kg per min i.v. resulted in plasma ANP concentrations of 3.9-4.8 ng/ml that remained relatively constant for 4 h. Treatment with CGS 34225 at 10 mgEq/kg, p.o., increased the ANP level to 7.7+/-1.0 and 10.6+/-1.8 ng/ml at 1 and 4 h after dosing (P<0.05, both times). These data demonstrate that CGS 34225 is a potent, orally active and long-acting inhibitor of ECE-1 and NEP in vivo. It is anticipated that compounds with this dual function may be useful in the treatment of cardiovascular diseases where the ET system plays a pathogenic role and the potentiation of ANP elicits therapeutic benefits.