Discovery of non-peptidic P2-P3 butanediamide renin inhibitors with high oral efficacy.

A new series of non-peptidic renin inhibitors having a 2-substituted butanediamide moiety at the P2 and P3 positions has been identified. The optimized inhibitors have IC50 values of 0.8 to 1.4 nM and 2.5 to 7.6 nM in plasma renin assays at pH 6.0 and 7.4, respectively. When evaluated in the normotensive cynomolgus monkey model, two of the most potent inhibitors were orally active at a dose as low as 3 mg/kg. These potent renin inhibitors are characterized by oral bioavailabilities of 40 and 89% in the cynomolgus monkey. Inhibitor 3z (BILA 2157 BS) was selected as candidate for pre-development.

Novel small renin inhibitors containing 4,5- or 3,5-dihydroxy-2-substituted-6-phenylhexanamide replacements at the P2-P3 sites.

Renin inhibitors containing a 4,5- or a 3,5-dihydroxy-2-substituted-6-phenylhexanamide fragment at the P2-P3 sites have been prepared and evaluated. The four possible diastereomeric diols of the two series of inhibitors were synthesized to determine the optimal configuration of the carbinol centers for these replacements. The most potent inhibitors of each series, la and 2c have a molecular weight of only 503 and IC50 values of 23 and 20 nM in a human plasma renin assay at pH 6.0. Their very low aqueous solubility limited their further evaluation. The efficacy of these P2-P3 replacements is a result of their ability to maintain the important hydrogen-bonds with the enzyme. Due to conformational differences with the dipeptide, adjustment at the P2 side chain was required. These 4,5- and 3,5-dihydroxyhexanamide segments could be seen as novel N-terminal dipeptide replacements.

A novel renal hypertensive guinea pig model for comparing different inhibitors of the renin-angiotensin system.

The present study describes a novel renal hypertensive guinea pig model for comparing different inhibitors of the renin-angiotensin system (RAS). Renal hypertension was induced by a two-step procedure consisting of ligation of the left caudal renal artery and right nephrectomy. Sham-operated animals were used as controls. Arterial blood pressure and heart rate were monitored in conscious animals. Left caudal renal artery ligation and subsequent right nephrectomy led to a significant increase (32% over sham-operated controls, p < .05) in mean arterial blood pressure (MABP), 3 to 4 weeks following surgery. Renal hypertensive animals had increased urine production (from 63 +/- 8 mL/kg per day to 143 +/- 29 mL/kg per day, p < .05) and an increased incidence of proteinuria (11/13 animals had urine protein levels higher than 20 mg/kg per day). Five of the 13 renal hypertensive animals also had hematuria. On autopsy, an 83% increase in the left kidney/body weight ratio and a 37% increase in the heart/body weight ratio were observed in the renal hypertensive animals, compared to the sham-operated controls. Changes in blood pressure and heart rate were assessed before and after an intravenous bolus injection of the drug to be tested. Captopril reduced MABP in both sham-operated and renal hypertensive animals with equal efficacy (up to a maximum of 42%). In contrast, BILA 2157 BS, one of our human renin inhibitors, produced a similar maximum MABP decrease but only in renal hypertensive animals. This selective antihypertensive effect was also observed with enalkiren, another renin inhibitor. These results indicate that the renal hypertensive guinea pig is an useful model for comparing and contrasting different RAS inhibitors.

Comparative studies on differential inhibition of the renin - angiotensin system in the anesthetized guinea pig.

The present study compares the hemodynamic effects and mechanisms of action of angiotensin II (AngII) antagonists, angiotensin converting enzyme (ACE) inhibitors, and renin inhibitors in the guinea pig, an animal with high similarity to primates in terms of in vitro and in vivo responses to several human renin inhibitors. Animals were anesthetized with urethane and ketamine. The carotid artery was catheterized for monitoring blood pressure and heart rate. After 30 min stabilization, drug (or vehicle) effects were monitored for 1 h following each increasing dose (i.v. bolus injection). Drugs tested include losartan, an AngII receptor antagonist; two renin inhibitors, BILA 2157 BS and PD-134672; and captopril, an ACE inhibitor. All drugs dose dependently decreased blood pressure. Diastolic blood pressure was reduced more than systolic blood pressure, suggestive of vasodilation. The maximum decrease (32 +/- 6%, p < 0.05 vs. vehicle) in mean arterial blood pressure (MABP) by losartan was achieved with a dose of 1 mg/kg. A similar decrease in MABP was observed with renin inhibitors at a dose of 3 mg/kg, without affecting heart rate. A further increase in the dose of renin inhibitors (6 mg/kg) decreased not only blood pressure but also heart rate. Captopril decreased MABP with a maximum of 48 +/- 3% (p < 0.05 vs. vehicle, losartan, and PD-134672). In the presence of HOE-140, a bradykinin antagonist, the MABP decrease by captopril was only 35 +/- 4%, (p < 0.05 vs. captopril alone). Bilateral nephrectomy reduced the peak MABP effect of PD-134672 by 67%, while the effects of captopril on MABP were affected to a lesser degree (57%). Therefore, captopril remains more effective in reducing MABP (p < 0.05 vs. that of PD-134672). These results suggest that renin inhibitors and AngII antagonists act more specifically on the renin - angiotensin system cascade, while captopril acts partially by a bradykinin-dependent mechanism. The small animal model described provides a novel tool for the comparative pharmacologic assessment of different renin - angiotensin system inhibitors.

3-Azi-1-methoxybutyl beta-D-galactopyranoside, a photoaffinity label for monoclonal antigalactan antibodies of the VH GAL 39.1/55.1 gene-family.

3-Azi-1-methoxybutyl beta-D-galactopyranoside, prepared from 2,3,4,6-tetra-O-acetyl-alpha-D-galactopyranosyl bromide in four steps, had an affinity constant for antigalactans IgA (Fab') J539 and X24 of 1550 and 1730 M-1, respectively. 3-Azi-1-methoxybutyl beta-D-(4-3H)galactopyranoside, when photolysed in the presence of IgA X24, specifically labelled the galactan-binding area of the immunoglobulin.