Harmony Biosciences Holdings, Inc. (Nasdaq: HRMY) announced today that it will present new clinical data on its investigational therapy EPX-100 (clemizole hydrochloride) at the upcoming 36th International Epilepsy Congress (IEC) in Lisbon, Portugal (Aug. 30 – Sept. 3, 2025). Poster presentations will feature interim updates from two pivotal Phase 3 studies—ARGUS in Dravet syndrome (DS) and LIGHTHOUSE in Lennox-Gastaut syndrome (LGS).
Science Significance
EPX-100 is an oral liquid formulation designed to modulate serotonin signaling via 5-hydroxytryptamine receptors, a novel mechanism in treatment-resistant epileptic encephalopathies. Developed using a phenotype-based zebrafish screening platform, EPX-100 represents an innovative preclinical-to-clinic trajectory. In zebrafish models harboring SCN1A mutations, which mimic the pathophysiology of Dravet syndrome, EPX-100 has shown seizure-modifying potential. If successful, this mechanism could open new therapeutic avenues for other sodium-channel–linked epilepsies.
Regulatory Significance
Both the ARGUS and LIGHTHOUSE trials are multicenter, randomized, double-blind, placebo-controlled Phase 3 studies, a critical stage for potential FDA and EMA regulatory submissions. Dravet syndrome and Lennox-Gastaut syndrome remain areas of high unmet medical need with limited FDA-approved therapies. Successful Phase 3 outcomes could position EPX-100 for orphan drug designation expansion, breakthrough therapy designation, and eventual marketing authorization in the U.S. and Europe.
Business Significance
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For Harmony, a company with an established footprint in rare neurological diseases, EPX-100 represents a pipeline diversification strategy beyond its commercial narcolepsy portfolio. The program underscores Harmony’s ambition to expand into rare epilepsies with significant market potential—Dravet syndrome alone has an incidence of 1:15,700, and Lennox-Gastaut affects ~48,000 patients in the U.S. Analysts view this as a high-value inflection point for Harmony’s mid-decade growth trajectory, potentially enhancing shareholder value and positioning the company as a leader in pediatric neurology.
Patients’ Significance
Patients and families affected by DS and LGS face severe, lifelong impacts—frequent and refractory seizures, cognitive impairment, and elevated risk of sudden unexpected death in epilepsy (SUDEP). Current treatments are limited and often provide incomplete seizure control. A successful EPX-100 program could represent meaningful improvement in quality of life, offering both symptomatic seizure reduction and potential neurodevelopmental benefits.
Policy Significance
The presentation comes at a time when global health policy increasingly prioritizes rare disease innovation. Initiatives in the U.S. (such as the Orphan Drug Act and Rett Syndrome Research Amendments) and Europe’s rare disease frameworks have created incentives for companies like Harmony to invest in novel therapies. Regulatory outcomes from EPX-100 could serve as a case study in accelerating translational science from zebrafish discovery to human clinical success under supportive rare disease policies.
Transaction Highlights
Presentation Dates: August 31 – September 2, 2025, IEC, Lisbon, Portugal.
ARGUS Trial (Dravet Syndrome): Phase 3, oral EPX-100, ILAE YES poster tour (Aug. 31, 2:00–2:30 p.m. GMT).
LIGHTHOUSE Trial (Lennox-Gastaut Syndrome): Phase 3, multicenter, randomized, double-blind, placebo-controlled; poster on Aug. 31.
Drug Candidate: EPX-100 (clemizole hydrochloride), twice-daily oral liquid targeting serotonin pathways.
Clinical Need: DS incidence ~1:15,700; LGS prevalence ~48,000 U.S. patients; both drug-resistant epileptic encephalopathies.
Corporate Strategy: Expanding Harmony’s rare neurology pipeline beyond sleep-wake disorders.
Source: Harmony Biosciences Press Release
