Robert R. Singhaus

3-(3-Aryloxyaryl)imidazo[1,2-a]pyridine sulfones as liver X receptor agonists.

Replacement of a quinoline with an imidazo[1,2-a]pyridine in a series of liver X receptor (LXR) agonists incorporating a [3-(sulfonyl)aryloxyphenyl] side chain provided high affinity LXR ligands 7. In functional assays of LXR activity, good agonist potency and efficacy were found for several analogs.

Discovery of a First-in-Class Receptor Interacting Protein 1 (RIP1) Kinase Specific Clinical Candidate (GSK2982772) for the Treatment of Inflammatory Diseases

RIP1 regulates necroptosis and inflammation and may play an important role in contributing to a variety of human pathologies, including immune-mediated inflammatory diseases. Small-molecule inhibitors of RIP1 kinase that are suitable for advancement into the clinic have yet to be described. Herein, we report our lead optimization of a benzoxazepinone hit from a DNA-encoded library and the discovery and profile of clinical candidate GSK2982772 (compound 5), currently in phase 2a clinical studies for psoriasis, rheumatoid arthritis, and ulcerative colitis. Compound 5 potently binds to RIP1 with exquisite kinase specificity and has excellent activity in blocking many TNF-dependent cellular responses. Highlighting its potential as a novel anti-inflammatory agent, the inhibitor was also able to reduce spontaneous production of cytokines from human ulcerative colitis explants. The highly favorable physicochemical and ADMET properties of 5, combined with high potency, led to a predicted low oral dose in humans.

4-(3-Aryloxyaryl)quinoline sulfones are potent liver X receptor agonists.

A series of 4-(3-aryloxyaryl)quinolines with sulfone substituents on the terminal aryl ring (7) was prepared as LXR agonists. High affinity LXR ligands with excellent agonist potency and efficacy in functional assays of LXR activity were identified. In general, these sulfone agonists were equal to or superior to previously described alcohol and amide analogs in terms of affinity, functional potency, and microsomal stability. Many of the sulfones had LXRbeta binding IC(50) values <10nM while the most potent compounds in an ABCA1 mRNA induction assay in J774 mouse cells had EC(50) values <10nM and were as efficacious as T0901317.

Biarylether amide quinolines as liver X receptor agonists.

A series of 4-(amido-biarylether)-quinolines was prepared as potential LXR agonists. Appropriate substitution with amide groups provided high affinity LXR ligands, some with excellent potency and efficacy in functional assays of LXR activity. Novel amide 4g had a binding IC(50)=1.9 nM for LXRbeta and EC(50)=34 nM (96% efficacy relative to T0901317) in an ABCA1 gene expression assay in mouse J774 cells, demonstrating that 4-(biarylether)-quinolines with appropriate amide substitution are potent LXR agonists.

The Identification and Pharmacological Characterization of 6-(tert-Butylsulfonyl)-N-(5-fluoro-1H-indazol-3-yl)quinolin-4-amine (GSK583), a Highly Potent and Selective Inhibitor of RIP2 Kinase

RIP2 kinase is a central component of the innate immune system and enables downstream signaling following activation of the pattern recognition receptors NOD1 and NOD2, leading to the production of inflammatory cytokines. Recently, several inhibitors of RIP2 kinase have been disclosed that have contributed to the fundamental understanding of the role of RIP2 in this pathway. However, because they lack either broad kinase selectivity or strong affinity for RIP2, these tools have only limited utility to assess the role of RIP2 in complex environments. We present, herein, the discovery and pharmacological characterization of GSK583, a next-generation RIP2 inhibitor possessing exquisite selectivity and potency. Having demonstrated the pharmacological precision of this tool compound, we report its use in elucidating the role of RIP2 kinase in a variety of in vitro, in vivo, and ex vivo experiments, further clarifying our understanding of the role of RIP2 in NOD1 and NOD2 mediated disease pathogenesis.

4-(3-Aryloxyaryl)quinoline alcohols are liver X receptor agonists

A series of 4-(3-aryloxyaryl)quinolines with alcohol substituents on the terminal aryl ring was prepared as potential LXR agonists, in which an alcohol group replaced an amide in previously reported amide analogs. High affinity LXR ligands with excellent agonist potency and efficacy in a functional model of LXR activity were identified, demonstrating that alcohols can substitute for amides while retaining LXR activity. The most potent compound was 5b which had an IC(50)=3.3 nM for LXRbeta binding and EC(50)=12 nM (122% efficacy relative to T0901317) in an ABCA1 mRNA induction assay in J774 mouse cells.

Identification of Quinoline-Based RIP2 Kinase Inhibitors with an Improved Therapeutic Index to the hERG Ion Channel

RIP2 kinase was recently identified as a therapeutic target for a variety of autoimmune diseases. We have reported previously a selective 4-aminoquinoline-based RIP2 inhibitor GSK583 and demonstrated its effectiveness in blocking downstream NOD2 signaling in cellular models, rodent in vivo models, and human ex vivo disease models. While this tool compound was valuable in validating the biological pathway, it suffered from activity at the hERG ion channel and a poor PK/PD profile thereby limiting progression of this analog. Herein, we detail our efforts to improve both this off-target liability as well as the PK/PD profile of this series of inhibitors through modulation of lipophilicity and strengthening hinge binding ability. These efforts have led to inhibitor 7, which possesses high binding affinity for the ATP pocket of RIP2 (IC50 = 1 nM) and inhibition of downstream cytokine production in human whole blood (IC50 = 10 nM) with reduced hERG activity (14 μM).