Optimization and Characterization of SHIP1 Ligands for Cellular Target Engagement and Activity in Alzheimer's Disease Models.

SHIP1 is a lipid phosphatase that negatively regulates immune receptor signaling in hematopoietic cells and microglia. SAR studies guided by biochemical and cellular assays using multiple human and murine protein constructs and cells identified 3-((2-chlorobenzyl)oxy)-5-(1-(piperidin-4-yl)-1H-pyrazol-4-yl)pyridine (32), which demonstrates SHIP1 target engagement, brain exposure, and evidence of a central pharmacodynamic response in vivo. In a protein-lipid overlay assay, compound 32 induced changes in the relative association of SHIP1 with phosphatidylinositols on a membrane surface. A thermal shift assay demonstrated cellular target engagement. Lipidomics revealed changes in the overall phosphoinositide pool consistent with target engagement and changes in phospho-AKT levels in THP-1 cells. Compound 32 enhanced uptake of myelin/membrane debris and amyloid by murine microglia, phenocopying reduced SHIP1 expression. Oral administration of 32 resulted in brain exposure sufficient to alter gene expression and reduce IL-1β levels as pharmacodynamic markers of microglial activation and neuroinflammation in an amyloidosis mouse model of Alzheimer's disease.