EPX-300 is a medicine approved by the U.S. Food and Drug Administration (FDA) as an antidepressant, anti-anxiety, and sleep-inducing insomnia therapy.

EPX-300 also is being studied by Epygenix Therapeutics as a treatment for Dravet syndrome. It was granted orphan drug designation by the FDA in August 2017 for treating Dravet.

How EPX-300 works

Dravet syndrome is a rare childhood disease and lifelong form of epilepsy, which usually starts in the first year of life with frequent or prolonged seizures. The main cause of the disease is a mutation in the SCN1A gene, but it is not fully understood how this mutation leads to the development of seizures.

Brain cells communicate with each other by sending electrical signals. When an electric signal reaches a synapse or connection between two nerve cells, it induces the release of chemical substances known as neurotransmitters. These neurotransmitters are responsible for transporting this signal to the next brain cell. Serotonin is one such neurotransmitter. Scientists think that in Dravet syndrome patients the serotonin-signaling pathway is altered, but exact effects are not known.

EPX-300 works by acting on the serotonin-signaling pathways. It is thought that it acts on the message-sending brain cells, preventing serotonin re-uptake. However, it is still not clear how EPX-300 precisely affects serotonin systems in the brain to improve seizures.

Studies of EPX-300

EPX-300 was discovered in a study that tested more than 3,000 approved medications in zebrafish with a mutation in the SCN1A gene repeating spontaneous seizure activity and mimicking the convulsive behavioral movements observed in Dravet syndrome patients. The zebrafish harbors 82 percent of human disease-associated genes and shares many physiological and metabolic pathways with humans.

Researchers aimed to identify compounds that suppressed neurological symptoms associated with the disease. Among the medications tested, researchers learned that EPX-300 was a powerful suppressor of spontaneous convulsive behavior and seizures in the fish. The study, “Drug screening in Scn1a zebrafish mutant identifies clemizole as a potential Dravet syndrome treatment” was published in the journal Nature Communications in 2013.

Other details

Epygenix is working on two other potential treatments for Dravet syndrome called EPX-100 and EPX-200 identified during the same zebrafish screening.


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