Motivation/problem statement: Alzheimer’s disease (AD) is a progressive neurodegenerative disease. No therapy has been found to alter its progression. Increasing evidence points to a deterioration of the blood brain barrier (BBB) and to the dysfunctionality of the neurovascular unit (NVU) as key components in AD. Wnt pathway regulates multiple cellular processes. Importantly, it maintains neurovascular functions, and evidence indicates Wnt pathway downregulation in AD. Carboxylesterase Notum is a secreted enzyme that inhibits Wnt signalling. Notum is increased in mouse models of AD and in AD patients, and is uniquely expressed in brain endothelial cells. Hence, inhibition of excessive Notum may help to restore the Wnt pathway and maintain a healthy NVU.
Methods/ approach: We tested our novel, CNS-penetrant, potent Notum inhibitor, ARUK3001185 in the APPPS1 mouse model of amyloid pathology and age-matched wild-type controls to evaluate effects of restoring NVU Wnt signalling via Notum inhibition. We studied the pharmacodynamic and pharmacokinetic profile of ARUK3001185 using immunohistochemistry and gene expression profiling to look at molecular changes in markers of Wnt signalling and also well described pathology in the APPPS1 mouse model.
Results: We confirmed in vitro that ARUK3001185 is highly selective for Notum by screening against serine hydrolases, kinases, and a panel of other drug targets. We confirmed good brain penetration in pharmacokinetic studies and confirmed it is well tolerated in vivo. In cortical microvessels, chronic treatment with ARUK3001185 altered expression of hundreds of genes previously associated with Wnt activation using a combination of RNAseq and the Nanostring NVU-targeted digital spatial profiling. We dosed 9m animals for 5 weeks and then took tissue to study the effects of Notum inhibition of neurovascular markers, amyloid pathology, inflammation and Wnt signalling markers.
Conclusion/implications: ARUK3001185 is a potent, selective and CNS penetrant inhibitor of Notum. Oral administration of ARUK3001185 in mouse changed the transcriptomic and proteomic profile of NVU-related cell types, while sparing total tissue changes. ARUK3001185 has been delivered to AD mouse models to identify potential therapeutic effects. We will present the effects of Notum inhibition on blood brain barrier proteins (Claudin-5), functional vasculature (fibrinogen extravasation), and pathological changes including levels of β-Amyloid, Gliosis (GFAP+/Iba1+ staining) and synapse and neuronal number in the APPPS1 mouse model.
