The RSK Inhibitor BIX02565 Limits Cardiac Ischemia/Reperfusion Injury.

Aims: During ischemia/reperfusion (I/R), ribosomal S6 kinase (RSK) activates Na(+)/H(+) exchanger 1 (NHE1) by phosphorylating NHE1 at serine 703 (pS703-NHE1), which promotes cardiomyocyte death and injury. Pharmacologic inhibition of NHE1 effectively protects animal hearts from I/R. However, clinical trials using NHE1 inhibitors failed to show benefit in patients with acute myocardial infarction (MI).

Mitigation of off-target adrenergic binding and effects on cardiovascular function in the discovery of novel ribosomal S6 kinase 2 inhibitors.

We previously reported the discovery of a novel ribosomal S6 kinase 2 (RSK2) inhibitor, (R)-5-Methyl-1-oxo-2,3,4,5-tetrahydro-1H-[1,4]diazepino[1,2-a] indole-8-carboxylic acid [1-(3-dimethylamino-propyl)-1H-benzoimidazol-2-yl]-amide (BIX 02565), with high potency (IC(50) = 1.1 nM) targeted for the treatment of heart failure. In the present study, we report that despite nanomolar potency at the target, BIX 02565 elicits off-target binding at multiple adrenergic receptor subtypes that are important in the control of vascular tone and cardiac function.

Indole RSK inhibitors. Part 1: discovery and initial SAR.

A series of inhibitors for the 90 kDa ribosomal S6 kinase (RSK) based on an 1-oxo-2,3,4,5-tetrahydro-1H-[1,4]diazepino[1,2-a]indole-8-carboxamide scaffold were identified through high throughput screening. An RSK crystal structure and exploratory SAR were used to define the series pharmacophore. Compounds with good cell potency, such as compounds 43, 44, and 55 were identified, and form the basis for subsequent kinase selectivity optimization.

Indole RSK inhibitors. Part 2: optimization of cell potency and kinase selectivity.

A series of inhibitors for the 90 kDa ribosomal S6 kinase (RSK) based on an 1-oxo-2,3,4,5-tetrahydro-1H-[1,4]diazepino[1,2-a]indole-8-carboxamide scaffold were optimized for cellular potency and kinase selectivity. This led to the identification of compound 24, BIX 02565, an attractive candidate for use in vitro and in vivo to explore the role of RSK as a target for the treatment heart failure.

Identification of pharmacological inhibitors of the MEK5/ERK5 pathway.

We have identified two novel MEK5 inhibitors, BIX02188 and BIX02189, which inhibited catalytic function of purified, MEK5 enzyme. The MEK5 inhibitors blocked phosphorylation of ERK5, without affecting phosphorylation of ERK1/2 in sorbitol-stimulated HeLa cells. The compounds also inhibited transcriptional activation of MEF2C, a downstream substrate of the MEK5/ERK5 signaling cascade, in a cellular trans-reporter assay system.

Glucose-regulated insulin production from genetically engineered human non-beta cells.

In this report we describe development and characterization of four human cell lines that are able to secrete insulin and C-peptide in response to higher concentrations of glucose. These cell lines have been developed by stably and constitutively expressing human proinsulin with a furin-cleavable site, whereas expression of furin is regulated by glucose concentration. These cell lines have been cloned and, therefore, the transgene in each cell is located in an identical location of the genome leading to a uniform expression.