Preclinical evaluation of potential nilotinib cardiotoxicity.

In vitro, concentrations ≥ 10 µM of nilotinib were needed to induce markers of cytotoxicity, apoptosis, and endoplasmic reticulum stress in both neonatal rat ventricular myocytes, a putative target tissue, and non-target heart fibroblasts, indicating a lack of cardiomyocyte-specific nilotinib toxicity in vitro. In rats, oral nilotinib treatment at 80 mg/kg for 4 weeks induced increased heart weight; however, this was not associated with relevant histopathological changes or effects on heart function. Thus, nilotinib at and above clinically relevant concentrations (4.27 µM) did not induce overt cardiovascular pathologies or heart failure in vitro or in vivo under study conditions.

Orally active MMP-1 sparing α-tetrahydropyranyl and α-piperidinyl sulfone matrix metalloproteinase (MMP) inhibitors with efficacy in cancer, arthritis, and cardiovascular disease.

α-Sulfone-α-piperidine and α-tetrahydropyranyl hydroxamates were explored that are potent inhibitors of MMP's-2, -9, and -13 that spare MMP-1, with oral efficacy in inhibiting tumor growth in mice and left-ventricular hypertrophy in rats and in the bovine cartilage degradation ex vivo explant system. α-Piperidine 19v (SC-78080/SD-2590) was selected for development toward the initial indication of cancer, while α-piperidine and α-tetrahydropyranyl hydroxamates 19w (SC-77964) and 9i (SC-77774), respectively, were identified as backup compounds.

Discovery of novel cyanodihydropyridines as potent mineralocorticoid receptor antagonists.

A new 1,4-dihydropyridine 5a, containing a cyano group at the C3 position, was recently reported to possess excellent mineralocorticoid receptor (MR) antagonist in vitro potency and no calcium channel-blocker (CCB) activity. In the present study, we report the structure-activity relationships of this novel series of cyano ester dihydropyridines that resulted in R6 substituted analogues with improved metabolic stability while maintaining excellent MR antagonist activity and selectivity against other nuclear receptors. Further structure optimization with the introduction of five-membered ring heterocycles at R6 resulted in compounds with excellent MR antagonist potency and a suitable pharmacokinetic profile. In vivo studies of a promising tool compound in the Dahl salt-sensitive rat model of hypertension showed similar blood pressure (BP) reduction as the steroidal MR antagonist eplerenone, providing proof-of-concept (POC) for a nonsteroidal, orally efficacious MR antagonist.

Discovery of (3S,3aR)-2-(3-chloro-4-cyanophenyl)-3-cyclopentyl-3,3a,4,5-tetrahydro-2H-benzo[g]indazole-7-carboxylic acid (PF-3882845), an orally efficacious mineralocorticoid receptor (MR) antagonist for hypertension and nephropathy.

We have discovered a novel class of nonsteroidal pyrazoline antagonists of the mineralocorticoid receptor (MR) that show excellent potency and selectivity against other nuclear receptors. Early analogues were poorly soluble and had a propensity to inhibit the hERG channel. Remarkably, both of these challenges were overcome by incorporation of a single carboxylate moiety. Structural modification of carboxylate-containing lead R-4g with a wide range of substituents at each position of the pyrazoline ring resulted in R-12o, which shows excellent activity against MR and reasonable pharmacokinetic profile. Introduction of conformational restriction led to a novel series characterized by exquisite potency and favorable steroid receptor selectivity and pharmacokinetic profile. Oral dosing of 3S,3aR-27d (PF-3882845) in the Dahl salt sensitive preclinical model of salt-induced hypertension and nephropathy showed blood pressure attenuation significantly greater than that with eplerenone, reduction in urinary albumin, and renal protection. As a result of these findings, 3S,3aR-27d was advanced to clinical studies.

Imatinib does not induce cardiotoxicity at clinically relevant concentrations in preclinical studies.

Cytotoxic concentrations of imatinib mesylate (10-50 microM) were required to trigger markers of apoptosis and endoplasmic reticulum stress response in neonatal rat ventricular myocytes and fibroblasts, with no significant differences observed between c-Abl silenced and nonsilenced cells. In mice, oral or intraperitoneal imatinib treatment did not induce cardiovascular pathology or heart failure. In rats, high doses of oral imatinib did result in some cardiac hypertrophy. Multi-organ toxicities may have increased the cardiac workload and contributed to the cardiac hypertrophy observed in rats only. These data suggest that imatinib is not cardiotoxic at clinically relevant concentrations (5 microM).

Analysis of protein fragmentation inhibition by an MMP-inhibitor in an in vivo model of heart failure using automated chromatography.

Proteomic strategies have continued to demonstrate value in studying disease by exploiting new technologies that can develop significant numbers of measurements from single samples. However, using complex samples such as tissues or blood has continued to be problematic due to the presence of major interfering substances. In this study, a process is described that uses denaturing peptide extraction from whole tissue and automated chromatography in order to allow subsequent analysis of more than 1000 tissue-derived peptides per sample. The process was employed to identify cardiac proteins that were spared degradation by administration of a heart-protecting matrix metalloproteinase (MMP) inhibitor (compound SC-621) following experimental myocardial infarction (MI). HPLC peptide fingerprints were developed from rat heart left ventricles and the resultant integrated peak data was compared across experimental animals. Surprisingly, although protein fragmentation was generally increased in MI hearts, the effect of the MMP inhibitor was only observed on a few species. The results from this study demonstrated that whole-tissue sample enrichment and peptide analysis using HPLC could be linked in order to study the effects of new compounds on a disease state. The system is flexible and amenable to improvements such as incorporating detection by mass spectrometry.