Objective

    Neuroinflammation plays a prominent role in the pathology of Alzheimer’s Disease (AD), including an increased activation of microglia and expression of pro-inflammatory cytokines. Colony stimulating factor 1 receptor (CSF1R) kinase activation regulates the proliferation of microglia and macrophage homeostasis. M-CSF (CSF-1) and IL-34 have been identified as activating ligands for CSF1R, with higher IL-34 expression reported in the developing and adult brain in comparison to CSF-1. Suppression of CSF1R activity via inhibiting the IL-34:CSF1R protein-protein interaction (PPI) may be a better therapeutic strategy for AD due to such tissue specificity of IL-34.

    An in-house fragment library of 1500 compounds was screened against immobilised IL-34 using Biacore SPR.  Dose-response hit validation and analogue screening resulted in a fragment lead series with reproducible binding of approximate K_D values ranging from 80-500µM. To locate the binding site of the fragments, in silico docking and mutagenesis studies have been performed, as well as large-scale protein production of IL-34 and glycan optimisation for X-ray crystallography. Finally, Biacore assay optimisation, further screening of elaborated compounds and hit validation by ligand-observed NMR were implemented to further the understanding of fragment structure-activity relationships.

    Our aim is to generate a chemical entity that is able to disrupt the IL34:CSF1R interaction and provide a novel therapeutic angle for Alzheimer’s Disease.