Therapeutic opportunities in Lafora disease, a rare juvenile neurodegenerative epilepsy with no treatment

Lafora disease (LD) is a progressive and fatal epilepsy with teenage-onset. It is caused by the accumulation of insoluble polyglucosans in neurons, determined by an increased glycogen production. At the molecular level, genetic alterations cause missing degradation of the PTG protein (Protein Targeting to Glycogen); knockout models validate PTG as a therapeutic target in Lafora disease. We aim at identifying small molecules halting and possibly reversing the course of Lafora disease.
A first drug repurposing approach will be explored by testing FDA-approved drugs in a newly developed Lafora disease model based on patients derived neural stem cells. This will be performed in high-throughput format using a phenotypic assay based on cellular polyglucosan quantification. In this context, we will also enlarge our biobank of LD patients stem cells.
A second, rational drug design pipeline will be applied to shape molecules on the PTG surface to interfere with its activation of glycogen synthesis. High-resolution three-dimensional structures of PTG in complex with carbohydrates and protein phosphatase 1, another protein regulating glycogen production, have already been determined by the collaborative network proposing the current project, together will the complete characterization of the binding affinities and their determinants. PTG surface has been scanned, and compounds potentially interfering with its function have been identified by molecular docking. These rationally identified compounds will be tested for their binding to PTG together with a blind crystallographic screening of about 2000 fragments. The development of PROTACs (PROteolysis Targeting Chimeras), leading to the proteasomal degradation of PTG, is planned.
As a third task, we will deepen our knowledge of the molecular basis of the disease by determining the crystallographic structures of LD-related macromolecular complexes, mainly focusing on the PTG/malin/laforin assembly. Malin and laforin are indeed the proteins mutated in LD; the molecular characterization of the above complex will constitute a prognostic tool to help predict the disease course in relation to the patient’s mutations.
In conclusion, the project will probe a new disease-modifying strategy to inform the development of novel therapies for LD, a severe pediatric epilepsy. A treatment option could then become available for LD patients in the short (drug repurposing) or medium term (new drug development with accelerated approval). The project will also make available to the scientific community a LD biobank, a LD phenotypic assay and the structure of the LD main molecular determinants.