Discovery of Clinical Candidate NT-0796, a Brain-Penetrant and Highly Potent NLRP3 Inflammasome Inhibitor for Neuroinflammatory Disorders.

The NLRP3 inflammasome is a component of the innate immune system involved in the production of proinflammatory cytokines. Neurodegenerative disorders, including Alzheimer's disease, Parkinson's disease, multiple sclerosis, and amyotrophic lateral sclerosis, have been shown to have a component driven by NLRP3 inflammasome activation. Diseases such as these with large unmet medical needs have resulted in an interest in inhibiting the NLRP3 inflammasome as a potential pharmacological treatment, but to date, no marketed drugs specifically targeting NLRP3 have been approved. Furthermore, the requirement for CNS-penetrant molecules adds additional complexity to the search for NLRP3 inflammasome inhibitors suitable for clinical investigation of neuroinflammatory disorders. We designed a series of ester-substituted carbamate compounds as selective NLRP3 inflammasome inhibitors, leading to NT-0796, an isopropyl ester that undergoes intracellular conversion to NDT-19795, the carboxylic acid active species. NT-0796 was shown to be a potent and selective NLRP3 inflammasome inhibitor with demonstrated in vivo brain penetration.

Discovery and Optimization of Triazolopyrimidinone Derivatives as Selective NLRP3 Inflammasome Inhibitors.

The NLRP3 inflammasome is a multiprotein complex that facilitates activation and release of the proinflammatory cytokines interleukin-1ß (IL-1ß) and IL-18 in response to infection or endogenous stimuli. It can be inappropriately activated by a range of danger signals resulting in chronic, low-grade inflammation underlying a multitude of diseases, such as Alzheimer's disease, Parkinson's disease, osteoarthritis, and gout. The discovery of potent and specific NLRP3 inhibitors could reduce the burden of several common morbidities. In this study, we identified a weakly potent triazolopyrimidone hit (1) following an in silico modeling exercise. This was optimized to furnish potent and selective small molecule NLRP3 inflammasome inhibitors. Compounds such as NDT-30805 could be useful tool molecules for a scaffold-hopping or pharmacophore generation project or used as leads toward the development of clinical candidates.

Structure-guided evolution of potent and selective CHK1 inhibitors through scaffold morphing.

Pyrazolopyridine inhibitors with low micromolar potency for CHK1 and good selectivity against CHK2 were previously identified by fragment-based screening. The optimization of the pyrazolopyridines to a series of potent and CHK1-selective isoquinolines demonstrates how fragment-growing and scaffold morphing strategies arising from a structure-based understanding of CHK1 inhibitor binding can be combined to successfully progress fragment-derived hit matter to compounds with activity in vivo. The challenges of improving CHK1 potency and selectivity, addressing synthetic tractability, and achieving novelty in the crowded kinase inhibitor chemical space were tackled by multiple scaffold morphing steps, which progressed through tricyclic pyrimido[2,3-b]azaindoles to N-(pyrazin-2-yl)pyrimidin-4-amines and ultimately to imidazo[4,5-c]pyridines and isoquinolines. A potent and highly selective isoquinoline CHK1 inhibitor (SAR-020106) was identified, which potentiated the efficacies of irinotecan and gemcitabine in SW620 human colon carcinoma xenografts in nude mice.