Harmony Biosciences' EPX-100 Shows ~50% Seizure Reduction And Favorable Safety In Dravet Syndrome Phase 3 Extension Data Presented At AES 2025

Data presented at the 2025 American Epilepsy Society Annual Meeting

Harmony Biosciences Holdings, Inc. (NASDAQ:HRMY), today announced the presentation of initial open-label extension (OLE) data from the company's ongoing Phase 3 ARGUS trial investigating EPX-100 (clemizole hydrochloride) for the treatment of Dravet syndrome (DS), which showed clinically meaningful reductions in seizure activity in participants with DS along with a favorable benefit-risk profile.

The data from poster #3.353will be presented at the American Epilepsy Society (AES) Annual Meeting in Atlanta, Ga., on Monday, December 8, from 12:00 pm – 1:45 pm ET.

Data from the eighteen participants in the OLE trial with at least six months' exposure to EPX-100 demonstrated the following:

• A median reduction of approximately 50% in countable motor seizure frequency per 28 days (CMS-28)
• 50% of these participants achieved at least a 50% reduction in CMS-28
• EPX-100 was generally well-tolerated in participants receiving treatment for more than two years and approaching three years in the OLE phase
• The most common treatment emergent adverse events (> 5%) were seizures, pyrexia and upper respiratory tract infection
• There were no significant gastrointestinal adverse events (2%) and no additional laboratory testing or special monitoring is being performed in the trial

These data suggest a positive emerging benefit-risk profile for EPX-100, supported by clinically meaningful reduction in seizure frequency and a favorable safety/tolerability profile.