Mechanisms of Tolerance to Chronic mGluR5 Inhibition

Over the past few years, both Novartis and Roche sponsored large-scale clinical trials of metabotropic glutamate receptor 5 (mGlu5) negative allosteric modulators (NAMs) to treat Fragile X syndrome (FXS). With a $90,000 grant from FRAXA Research Foundation in 2015-2017, Dr. Mark Bear’s team will explore if mGlu5 NAMs dosed chronically causes tolerance, and if so, how it develops and to probe new avenues to prevent or circumvent it.

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Clinical Trial of Ganaxolone in Patients with Fragile X Syndrome

Frank Kooy, PhD, at University of Antwerp

With a $90,000 grant from FRAXA Research Foundation funded during 2014-2015, Dr. Frank Kooy and colleagues at the University of Antwerp are conducting a double blind crossover trial of ganaxolone in patients with Fragile X syndrome. Results of this study were mixed (see Marinus: Results from Phase 2 Exploratory Clinical Study Support Continued Development of Ganaxolone in Fragile X Syndrome.)

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Fragile X Mutant Mouse Models

David Nelson, PhD, FRAXA Investigator

With $375,000 in grants from the FRAXA Research Foundation since 2009, Dr. David Nelson has developed an impressive array of advanced mouse models of Fragile X, at Baylor College of Medicine. These models are available to investigators worldwide on request. This resource has been essential for a broad, rapid distribution of Fragile X and related gene mouse models and has increased the pace of Fragile X research.

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Repurposing Drugs to Dampen Hyperactive Nonsense-Mediated Decay in Fragile X Syndrome

With a $90,000 grant from the FRAXA Research Foundation, Dr. Lynne Maquat and Dr. Tatsuaki Kurosaki will investigate nonsense-mediated mRNA decay (NMD) in Fragile X. NMD is a “housekeeping” process that cells use to prevent faulty proteins from being made. But there is too much of it in Fragile X syndrome. There are already available drugs that suppress NMD – including caffeine.

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Fruit Flies to Model and Test Fragile X Treatments

Dr. Tom Jongens and Dr. Sean McBride study Fragile X Fruit Flies

Dr. Jongens and his collaborators have found an insulin-like protein in the fly brain that is overexpressed in the Fragile X mutant fly, leading to increased activity of the insulin signaling pathway. Furthermore, they found that certain behavioral patterns in the Fragile X flies can be rescued by expressing the FX gene just in insulin producing neurons in the fly brain. In the mutant, there are other changes in the signaling pathways, including a decrease in cAMP and elevation in PI3K, mTOR, Akt and ERK activity. They now propose to study 2 medicines used for diabetes: pioglitazone (increases cAMP and decreases Akt and ERK) and metformin (inhibits mTOR), in flies and mice to validate the potential efficacy of these novel therapeutics for Fragile X.

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FRAXA Grant to Nahum Sonenberg, PhD — Effects of metformin in Fmr1 knockout mouse model of Fragile X syndrome

Nahum Sonenberg

Mis-regulation of activity-dependent protein synthesis is one of the major cellular abnormalities found in Fragile X. Upstream neuronal signaling regulates a large cluster of enzymes called the mTORC1 complex, which in turn regulates protein synthesis. This complex is also controlled by cellular energy levels via the metabolic sensor AMP-activated Protein Kinase (AMPK). AMPK is a highly conserved kinase that is activated under conditions of energy stress, when intracellular ATP levels decline and intracellular AMP increases.

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