Herman H. Stein

Highly potent and specific inhibitors of human renin

We have designed and synthesized a series of small peptides containing a perfluoroalkyl ketone group at the C‐terminal position of the angiotensin I sequence as inhibitors of human renin. From this series of compounds, 8 and 10 showed strong inhibition of human renin (IC50 = 3 × 10−9, 7 × 10−9 M, respectively). Compound 10 did not inhibit pepsin and cathepsin D at 10−4 M. Comparison of the IC50 of compound 8 and compound 11 (8.7 × 10−7 M) demonstrated the marked effect of the perfluoropropyl group on the potency of inhibition on renin, presumably due to the strong electron‐withdrawing effect causing the ketone in 8 to exist predominantly as the hydrate — thus mimicking the tetrahedral transition state during hydrolysis of the scissile Leu10—Val11 amide bond.

Modified peptides which display potent and specific inhibition of human renin

A new class of angiotensinogen analogues which contain heteroatom-methylene and retro-inverso amide bond replacements was synthesized and evaluated for renin inhibition. Selected compounds in the series were specific for renin over other aspartic proteinases, and the most potent inhibitor demonstrated hypotensive activity in a salt depleted monkey.

Renin inhibitors Improvements in the stability and biological activity of small peptides containing novel Leu‐Val replacements

We have designed a novel class of potent (0.3–7 nM) renin inhibitors which contain a dihydroxyethylene replacement for what is formally the Leu1O‐Val11 amide bond. Good potency (0.6 nM), water solubility (> 10 mg/ml at 37°C), stability toward degradation by chymotrypsin (t =82O min), and in vivo activity in a primate model (15% drop in mean arterial pressure in association with complete inhibition of plasma renin activity) are properties which have been incorporated into compound 10, an interesting new agent to be used in the study of hypertension.

Peptide analogues of angiotensinogen effect of peptide chain length on renin inhibition

Renin inhibition was evaluated for a series of peptide analogues of angiotensinogen with different chain lengths. Systematic deletion of amino acid residues from the hexapeptide BocPheHisLeuR-ValIleHisOCH3 showed that the presence of residues at the N-terminal Phe and His positions was essential for efficient enzyme-inhibitor binding whereas the C-terminal Ile and His residues were much less important. Synthesis of a tetrapeptide analogue shortened at the C-terminus and containing modified side chains produced a potent inhibitor of renin which demonstrated hypotensive activity in a salt depleted monkey.

Conformationally restricted peptide isosteres. 2.1 Synthesis and in vitro potency of dipeptide renin inhibitors employing a 2-alkylsulfonyl-3-phenylcyclopropane carboxamide as a P3 amino acid replacement ☆

Abstract A series of dipeptide renin inhibitors employing a 2,3-disubstituted cyclopropane carboxamide at the P3 position of the molecule were prepared by coupling racemic(IS,2R,3R) 2-alkylsulfonyl-3-phenyl(or cyclohexyl)cyclopropanecarboxylic acid with the amino acid derivatives 11a–d. The individual diastereomers were separated and tested for in vitro potency. IC50 values ranged from 0.37 to 1.4 nM and 5.8 to 29 nm against purified, pH 6.0 and plasma, pH 7.4 human renin, respectively. In all examples, the more polar diastereomer was the most potent.

Cardiovascular effects and hemodynamic mechanism of action of the novel, nonpeptidic renin inhibitor A-74273 in dogs.

Summary A-74273 is a nonpeptidic, potent inhibitor of human and canine renin (IC50 = 3.1 and 43 nM, respectively, in plasma at pH 7.4) and has been shown to be orally active in dogs. To determine the hemodynamic mechanism underlying this renin inhibitors hypotensive activity, the cardiac and hemodynamic effects of A-74273 were studied in sodium-depleted and sodium-replete pentobarbital-anesthetized dogs. Vehicle [5% dextrose in water (V, D5W), n = 8] or a single dose of A-74273 was administered intravenously (i.v.) as a bolus followed by a 30-min infusion (one tenth the bolus dose per minute). Baseline mean arterial pressure (MAP) was similar among all treatment groups, but baseline plasma renin activity (PRA) was increased in the sodium-depleted dogs as compared with the sodium-replete dogs. In sodium-depleted dogs (n = 7–8/dose), MAP decreased maximally as compared with baseline by 4 ± 1, 19 ± 3, and 23 ± 3% during infusion of A-74273 at doses of 0.001, 0.01, and 0.1 mg/ kg/min, respectively (p < 0.05 vs. baseline or V). The two highest infusion doses also produced significant reductions (p < 0.05 vs. baseline and V) in systemic vascular resistance (SVR, 21 ± 2 and 25 ± 2%) and left ventricular end-diastolic pressure (LVEDP, 40 ± 8 and 47 ± 12%). In sodium-replete dogs (n = 4/dose), an infusion dose of 0.01 mg/kg/min elicited no hemodynamic response, whereas 0.1 mg/kg/min reduced MAP by 13 ± 2% (p < 0.05 vs. baseline) and SVR by 7 ± 6%. A-74273 had no significant effect on cardiac output (CO), stroke volume (SV), and LV contractility. Heart rate (HR) either remained unchanged or decreased slightly. PRA was significantly decreased (p < 0.05 vs. baseline and V) during infusion of A-74273 at all doses except 0.01 mg/kg/min in sodium-replete dogs. Furthermore, PRA, MAP, SVR, and LVEDP exhibited dose-related recoveries, and the parallel recoveries of SVR and MAP reflected PRA. A-74273 behaves as a vasodilator through blockade of the renin-angiotensin system (RAS), and does so without inducing reflex tachycardia and without compromising cardiac function. Moreover, the results in sodium-depleted dogs suggest that increasing the dose of A-74273 preferentially prolongs duration of action without inducing profound hypotension.

Effects of high doses of A-74273, a novel nonpeptidic and orally bioavailable renin inhibitor

Previous studies with peptidic renin inhibitors have shown that high intravenous (i.v) doses can induce unexpectedly large decreases in blood pressure (BP) that appear to be independent of plasma renin inhibition. A-74273 represents a new class of potent and orally bioavailable nonpeptidic renin inhibitors. We evaluated the BP effects of this renin inhibitor administered orally (p.o.) or i.v. at high doses to conscious salt-depleted dogs. Administration of A-74273 at 30 and 60 mg/kg p.o. (n = 6 per dose) produced similar maximum reductions in BP (-40 ± 4 vs. −46 ± 5 mm Hg) despite the occurrence of greater plasma drug concentrations at the higher dose. Duration of hypotension, however, was increased (p < 0.05) from 9 h at 30 mg/kg to 18 h at 60 mg/kg. The initial depressor response to 10 and 30 mg/kg i.v. doses of A-74273 (n = 6 per dose) was comparable, although duration and overall BP response was greater at 30 mg/kg i.v. No BP responses to A-74273 were noted in salt-replete dogs (n = 5). The hypotension produced by 30 mg/kg p.o. A-74273 was completely reversed by norepinephrine (NE 5 μg/kg/min; n = 5) or isotonic saline (4 ml/min/kg, n = 5) infusion. These studies demonstrate that high doses of A-74273 result in predictable BP responses that are renin-dependent and reversible. Therefore, large decreases in BP with high doses is not an attribute common to all renin inhibitors but appears to be a function of the structural characteristics specific to a particular compound.

Slow, tight binding to human renin of some nonpeptidic renin inhibitors containing a 4‐methoxymethoxypiperidinylamide at the P4 position

A series of nonpeptidic human renin inhibitors with a 4‐methoxymethoxypiperidinylamide at the P4 position of the molecule exhibited slow tight binding to the enzyme. Replacement of the methoxymethoxy moiety on the piperidine ring with H, OH, methoxyethyl, propyloxy or n‐butyl eliminated the effect. The inhibition was partially reversed by prolonged dialysis at 4°C, arguing against formation of a covalent bond in the tightened complex.

Novel non-basic bioisostere of histidine synthesized from L-aspartic acid

The incorporation of the novel bioisostere (1c) of histidine into a tripeptide led to a very potent and specific renin inhibitor.

Renin inhibitors: C-terminal oxetanes as potent transition-state mimics

A novel transition-state mimic containing a C-terminal oxetane has been developed. Renin inhibitors incorporating this fragment exhibit enhanced potency against human plasma renin at physiological pH. The binding affinity of this new species has allowed size reductions at other sites.