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A series of 7,6- and 7,5-fused bicyclic thiazepinones and oxazepinones were generated and incorporated as conformationally restricted dipeptide surrogates in mercaptoacyl dipeptides. These compounds are potent inhibitors of angiotensin-converting enzyme (ACE) and neutral endopeptidase (NEP) both in vitro and in vivo. Compound 1a, a 7,6-fused bicyclic thiazepinone, demonstrated excellent blood pressure lowering in a variety of animal models characterized by various levels of plasma renin activity and significantly potentiated urinary sodium, ANP, and cGMP excretion in a cynomolgus monkey assay. On the basis of its potency and duration of action, compound 1a (BMS-186716) was advanced into clinical development for the treatment of hypertension and congestive heart failure.

Combined inhibition of neutral endopeptidase (NEP) and angiotensin converting enzyme (ACE) produces cardiovascular effects greater than those elicited by selective inhibition of either enzyme alone. Dual metalloprotease inhibitors are single molecules that inhibit both NEP and ACE and produce cardiovascular effects in animal models similar to those elicited by the combination of NEP and ACE inhibitors. The purpose of this study was to determined the duration of antihypertensive activity of the dual metalloprotease inhibitor omapatrilat in rodent models of hypertension. Omapatrilat inhibited NEP (Ki = 9 nmol/L) and ACE (Ki = 6 nmol/L) activities in vitro and inhibited the pressor response to angiotensin I in rats after intravenous administration with a potency and duration of action similar to those of the long acting ACE inhibitor fosinoprilat. After single dose administration, omapatrilat lowered mean arterial blood pressure (aortic catheter) in sodium depleted spontaneously hypertensive rats (high renin model) from 148+/-5 to 106+/-3 mm Hg (baseline to 24 h), in deoxycorticosterone acetate-salt hypertensive rats (low renin) from 167+/-4 to 141+/-5 mm Hg and in spontaneously hypertensive rats (normal renin) from 162+/-4 to 138+/-3 mm Hg (P < .05 at 24 h v vehicle in all models). After oral administration, omapatrilat (100 micromol/kg/day) persistently lowered systolic blood pressure (tail cuff) in spontaneously hypertensive rats during 11 days of treatment; at 24 h after dosing on day 12, mean arterial pressure (aortic catheter) was lower (P < .05) in the group receiving omapatrilat (133+/-5 mm Hg) than in the group receiving vehicle (149+/-2 mm Hg). The results indicate that omapatrilat is a potent dual metalloprotease inhibitor of NEP and ACE with long lasting, oral antihypertensive effects in low, normal, and high renin models of hypertension. Omapatrilat has the potential to be an effective, broad spectrum antihypertensive agent.

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Vasopeptidase inhibitors are single molecules that inhibit neutral endopeptidase (NEP) and angiotensin-converting enzyme (ACE) simultaneously. Omapatrilat, the first in this new class of cardiovascular agents, potentiates vasodilatory and cardioprotective peptides and represses angiotensin II. This study compared the effects of omapatrilat with those of a pure ACE inhibitor on cardiac geometry and survival in animals with heart failure. BIO TO-2 cardiomyopathic hamsters (CMHs) in the early stages of dilated heart failure were treated with vehicle or maximal ACE inhibitory doses of captopril (750 micromol/kg/day) or omapatrilat (200 micromol/kg/day). Prolonged vasopeptidase inhibition increased median survival time after the start of treatment by 99 and 31% compared with vehicle and captopril, respectively (median survival times: 146, 221, and 290 days with vehicle, captopril, and omapatrilat, respectively; p < 0.001 for all comparisons). In similar CMHs, captopril or omapatrilat administered for 2 months significantly (p < 0.05) decreased heart weight, pulmonary congestion (lung weight), and left ventricular (LV) chamber volume compared with vehicle. Omapatrilat significantly increased LV mass-to-volume ratio compared with vehicle and captopril. Omapatrilat, but not captopril, significantly increased urinary atrial natriuretic peptide excretion, indicating NEP inhibition. Thus vasopeptidase inhibition with omapatrilat was more effective than ACE inhibition with captopril in preventing changes in LV geometry and premature mortality in hamsters with dilated heart failure.

Angiotensin II and endothelin-1 activate their respective AT 1 and ET A receptors on vascular smooth muscle cells, producing vasoconstriction, and both peptides are implicated in the pathogenesis of essential hypertension. Angiotensin II potentiates the production of endothelin, and conversely endothelin augments the synthesis of angiotensin II. Both AT 1 and ET A receptor antagonists lower blood pressure in hypertensive patients; thus, a combination AT 1 /ET A receptor antagonist may have greater efficacy and broader utility compared with each drug alone. By rational drug design a biphenyl ET A receptor blocker was modified to acquire AT 1 receptor antagonism. These compounds (C and D) decreased Sar-Ile-Angiotensin II binding to AT 1 receptors and endothelin-1 binding to ET A receptors, and compound C inhibited angiotensin II-and endothelin-1-mediated Ca 2ϩ transients. In rats compounds C and D reduced blood pressure elevations caused by intravenous infusion of angiotensin II or big endothelin-1. Compound C decreased blood pressure in Na ϩ -depleted spontaneously hypertensive rats and in rats with mineralocorticoid hypertension. Compound D was more efficacious than AT 1 receptor antagonists at reducing blood pressure in spontaneously hypertensive rats, and its superiority was likely due to its partial blockade of ET A receptors. Therefore compounds C and D are novel agents for treating a broad spectrum of patients with essential hypertension and other cardiovascular diseases.

Extracts of atrial and ventricular rat heart tissue were prepared in phosphatebuffered saline and boiled (PBS-boiled) or in acetic acid and fractionated using Sephadex G-75. The extracts were injected intravenously into anesthetized nondiuretic (i.e., not hydrated) rats to assay for natriuretic activity. PBS-boiled atrial extract caused urinary sodium excretion (UNaV) to increase significantly (P < 0.05) by 672 5 307% (+SE) during the 10 min after injection; whereas no significant change in U,,V occurred after injection of PBS alone or ventricular extract. UKV and urine volume increased significantly by 400 + 236% and 499 5 105%, respectively, after injection of PBS-boiled atrial extract. Pooled active fractions from Sephadex (3-75 of acid atrial extract (lyophilized and reconstituted in PBS) caused UNaV and urine volume to increase significantly by 1015 5 401% and 807 + 291%, respectively, and a smaller but significant increase in UKV of 158 5 23%. The natriuretic activity of acid atrial extract eluted in the molecular weight range of 3600 to 44,OOO daltons, was unaffected by heating in a boiling water bath, treatment with concanavalin A, incubation with plasma, or removing the head of the assay rat, but was abolished by treatment with trypsin. These properties do not generally resemble those of the natriuretic factors in blood and urine previously reported by others. 502