ABSTRACT
Aldosterone synthase (CYP11B2) inhibitors have been explored in recent years as an alternative therapeutic option to mineralocorticoid receptor (MR) antagonists to reduce elevated aldosterone levels, which are associated with deleterious effects on various organ systems including the heart, vasculature, kidney, and central nervous system (CNS). A benzamide pyridine hit derived from a focused screen was successfully developed into a series of potent and selective 3-pyridyl isoindolin-1-ones CYP11B2 inhibitors. Our systematic structure-activity relationship study enabled us to identify unique structural features that result in high selectivity against the closely homologous cortisol synthase (CYP11B1). We evaluated advanced lead molecules, exemplified by compound 52, in an in vivo cynomolgus monkey acute adrenocorticotropic hormone (ACTH) challenge model and demonstrated a superior 100-fold in vivo selectivity against CYP11B1.
Subject(s)
Cytochrome P-450 CYP11B2/antagonists & inhibitors , Cytochrome P-450 Enzyme Inhibitors/chemistry , Cytochrome P-450 Enzyme Inhibitors/pharmacology , Drug Design , Isoindoles/chemistry , Pyridines/chemistry , Pyridines/pharmacology , Administration, Oral , Animals , Cytochrome P-450 Enzyme Inhibitors/administration & dosage , Cytochrome P-450 Enzyme Inhibitors/pharmacokinetics , Drug Stability , Humans , Models, Molecular , Molecular Conformation , Pyridines/administration & dosage , Pyridines/pharmacokinetics , Rats , Structure-Activity Relationship , Tissue DistributionABSTRACT
Inappropriately high levels of aldosterone are associated with many serious medical conditions, including renal and cardiac failure. A focused screen hit has been optimized into a potent and selective aldosterone synthase (CYP11B2) inhibitor with in vitro activity against rat, mouse, human, and cynomolgus monkey enzymes, showing a selectivity factor of 160 against cytochrome CYP11B1 in the last species. The novel tetrahydroisoquinoline compound (+)-(R)-6 selectively reduced aldosterone plasma levels in vivo in a dose-dependent manner in db/db mice and cynomolgus monkeys. The selectivity against CYP11B1 as predicted by cellular inhibition data and free plasma fraction translated well to Synacthen challenged cynomolgus monkeys up to a dose of 0.1 mg kg(-1). This compound, displaying good in vivo potency and selectivity in mice and monkeys, is ideally suited to perform mechanistic studies in relevant rodent models and to provide the information necessary for translation to non-human primates and ultimately to man.
Subject(s)
Cytochrome P-450 CYP11B2/antagonists & inhibitors , Enzyme Inhibitors/chemical synthesis , Enzyme Inhibitors/pharmacology , Mineralocorticoid Receptor Antagonists/chemical synthesis , Mineralocorticoid Receptor Antagonists/pharmacology , Tetrahydroisoquinolines/chemical synthesis , Tetrahydroisoquinolines/pharmacology , Aldosterone/blood , Animals , Drug Design , Drug Discovery , Humans , Macaca fascicularis , Male , Mice , Mice, Inbred DBA , Models, Molecular , RatsABSTRACT
OBJECTIVE: Magnetic resonance (MR) relaxometry has recently been introduced for noninvasive body composition analysis in awake mice. The purpose of the present study was to extend the method to rats and to introduce calibration procedures that render MR relaxometry fully quantitative. RESEARCH METHODS AND PROCEDURES: Proton T(2) MR relaxometry at 4.7 Tesla was used for body composition analyses in 700 awake mice and 400 rats of different strains and conditions. Relaxograms calculated from the signal decays observed with multi-spin-echo acquisition provided well-separated contributions of tissue water and fat. Analysis of fat composition was carried out in vivo using (13)C-MR spectroscopy. Evolution of body composition in rats was assessed during drug treatment. RESULTS: MR relaxometry for noninvasive body composition analysis in laboratory rodents was implemented on a standard MR scanner, and a throughput of >30 animals per hour was achieved. Excellent linearity and reproducibility with coefficients of variance as low as 2.5% and 1.7% were obtained in mice and rats, respectively. The lean mass-to-water ratio (mice, 1.35 +/- 0.03; rats, 1.39 +/- 0.04) and the proton density of fat (mice, 8.1 +/- 0.2; rats, 8.9 +/- 0.2 g/mol) were determined from cross-sectional data. Fat composition analysis by (13)C-MR spectroscopy corroborated these findings and yielded information on the average acyl chain length (16.3 +/- 1.6) and contributions of saturated (27 +/- 3%), monounsaturated (22 +/- 2%), and polyunsaturated (51 +/- 3%) fatty acids. Longitudinal assessments in rats treated with sibutramine and dexfenfluramine showed dose-related changes in body composition. DISCUSSION: T(2) MR relaxometry backed by solid calibration provides a powerful means for rapid quantitative body composition analysis in awake mice and rats that is suitable for serial investigations in pharmaceutical research.
