O-GlcNAcase Inhibitor ASN90 is a Multimodal Drug Candidate for Tau and α-Synuclein Proteinopathies

Abstract

Neurodegenerative proteinopathies are characterized by the intracellular formation of insoluble and toxic protein aggregates in the brain that are closely linked to disease progression. In Alzheimer’s disease and in rare tauopathies, aggregation of the microtubule-associated tau protein leads to the formation of neurofibrillary tangles (NFT). In Parkinson’s disease (PD) and other α-synucleinopathies, intracellular Lewy bodies containing aggregates of α-synuclein constitute the pathological hallmark. Inhibition of the glycoside hydrolase O-GlcNAcase (OGA) prevents the removal of O-linked N -acetyl- d -glucosamine (O-GlcNAc) moieties from intracellular proteins and has emerged as an attractive therapeutic approach to prevent the formation of tau pathology. Like tau, α-synuclein is known to be modified with O-GlcNAc moieties and in vitro these have been shown to prevent its aggregation and toxicity. Here, we report the preclinical discovery and development of a novel small molecule OGA inhibitor, ASN90. Consistent with the substantial exposure of the drug and demonstrating target engagement in the brain, the clinical OGA inhibitor ASN90 promoted the O-GlcNAcylation of tau and α-synuclein in brains of transgenic mice after daily oral dosing. Across human tauopathy mouse models, oral administration of ASN90 prevented the development of tau pathology (NFT formation), functional deficits in motor behavior and breathing, and increased survival. In addition, ASN90 slowed the progression of motor impairment and reduced astrogliosis in a frequently utilized α-synuclein-dependent preclinical rodent model of PD. These findings provide a strong rationale for the development of OGA inhibitors as disease-modifying agents in both tauopathies and α-synucleinopathies. Since tau and α-synuclein pathologies frequently co-exist in neurodegenerative diseases, OGA inhibitors represent unique, multimodal drug candidates for further clinical development.

Targeting O-GlcNAcylation to overcome resistance to anti-cancer therapies

“…We recently shown the efficiency of Thiamet-G to improve global O-GlcNAcylation levels and 5-FU response in murine carcinogen-induced CRC tumors (34). In addition, other selective OGA inhibitors, MK-8719 (143) and ASN120290 (previously known as ASN-561) (144) have obtained the orphan drug designation by the FDA for the treatment of the progressive supranuclear palsy (PSP) in 2016 and 2018 respectively. However, modulating global cellular O-GlcNAcylation levels have limits in term of therapeutic strategy.…”

Phosphorylated Tau in Alzheimer’s Disease and Other Tauopathies

“…The serine and threonine sites of tau are also affected by O-GlcNAcylation, many known O-GlcNAcylation sites are nearby or found to be overlapping with phosphorylation sites, and thus it has been suggested that these two could regulate phosphorylation positively or negatively. For instance, the inhibition of glycoside hydrolase O-GlcNAcase halts the removal of O-GlcNAc moieties from intracellular proteins that prevent developing tau pathology [ 56 ]. Recently, Yin and colleagues’ study showed that SIRT1 member of Sirtuins, a family of signaling proteins, increases the protein level of O-GlcNAcase by C/enhancer binding protein(C/EBPα).…”

Chemical Biology Approaches to Understanding Neuronal O−GlcNAcylation

“…To determine whether ASN90 promotes the O−GlcNAcylation of α‐synuclein in vivo , [39] the team employed a chemoenzymatic mass‐tagging method [47] that involves GalT‐mediated GalNAz labeling of native O−GlcNAc moieties on α‐synuclein, followed by a click reaction with dibenzocyclooctyne‐polyethylene glycol (PEG) probes [33] (Figure 2). In brain homogenates from PD mouse models, O−GlcNAcylated α‐synuclein tagged with the PEG probe resulted in a band (∼30 kDa) distinct from that of the unmodified protein (15 kDa) [39] . Using this assay, the team observed approximately 20% of total α‐synuclein modified by O−GlcNAc in vehicle‐treated controls, whereas chronic ASN90 treatment increased overall α‐synuclein O−GlcNAcylation by 1.5‐fold [39] .…”