Discovery and Development of Small-Molecule Inhibitors of Glycogen Synthase

Abstract

The overaccumulation of glycogen appears as a hallmark in various glycogen storage diseases (GSDs), including Pompe, Cori, Andersen, and Lafora disease. Accumulating evidence suggests that suppression of glycogen accumulation represents a potential therapeutic approach for treating these GSDs. Using a fluorescence polarization assay designed to screen for inhibitors of the key glycogen synthetic enzyme, glycogen synthase (GS), we identified a substituted imidazole, (rac)-2-methoxy-4-(1-(2-(1-methylpyrrolidin-2-yl)­ethyl)-4-phenyl-1H-imidazol-5-yl)­phenol (H23), as a first-in-class inhibitor for yeast GS 2 (yGsy2p). Data from X-ray crystallography at 2.85 Å, as well as kinetic data, revealed that H23 bound within the uridine diphosphate glucose binding pocket of yGsy2p. The high conservation of residues between human and yeast GS in direct contact with H23 informed the development of around 500 H23 analogs. These analogs produced a structure–activity relationship profile that led to the identification of a substituted pyrazole, 4-(4-(4-hydroxyphenyl)-3-(trifluoromethyl)-1H-pyrazol-5-yl)­pyrogallol, with a 300-fold improved potency against human GS. These substituted pyrazoles possess a promising scaffold for drug development efforts targeting GS activity in GSDs associated with excess glycogen accumulation.

GYS1 or PPP1R3C deficiency rescues murine adult polyglucosan body disease

“…The anticipated safety profile of GYS1 knockdown is furthermore favorable as humans with one null GYS1 allele are healthy 34 . GYS1 could be downregulated at the DNA, RNA, or protein levels, and progress is already being made at least in the latter with promising compounds including guaiacol 35 and imidazole analogs 36 . PPP1R3C deficiency has to date not been associated with a pathological state in humans.…”

Endocytosis of the glutamate transporter 1 is regulated by laforin and malin: Implications in Lafora disease

“…To date, four therapeutic approaches are being developed to treat LD (for the latest update see Gentry et al, 2020). These include the use of antisense oligonucleotides targeting glycogen synthase to avoid the formation of Lafora bodies, enzyme therapy directed to degrade them once formed (Brewer et al, 2019), the use of smallmolecule inhibitors of glycogen synthase (Tang et al, 2020), and the use of repurposing drugs such as metformin (Berthier et al, 2016), although none of them have been translated to the clinic yet. It is therefore of great importance to continue investigating the molecular mechanisms of the disease to find a good therapeutic target and an effective treatment that could be used in clinical trials.…”

Sensitive quantification of α-glucans in mouse tissues, cell cultures, and human cerebrospinal fluid

“…Monitoring glycogen synthesis in human cell culture is crucial in any therapeutic study targeting central enzymes of glycogen metabolism. For instance, glycogen synthase has been identified a therapeutic target in LD (13,43,44) and adult polyglucosan body disease (41).…”

“…For sole quantification of soluble and insoluble glycogen, especially in younger mice with less progressed glycogen accumulation, simpler methods requiring less tissue are favorable. Furthermore, sensitive detection of glycogen in cultured cells is prerequisite for the characterization of candidate therapeutics targeting, for instance, glycogen synthase in GSDs with glycogen overproduction (13). The detection of CSF biomarkers in neurodegenerative diseases is common (14).…”