Harmony Biosciences Holdings, Inc. (NASDAQ:HRMY) today announced that it will present encore open-label extension data from the company's investigation of EPX-100 (clemizole hydrochloride) in the ongoing Phase 3 ARGUS trial for the treatment of Dravet syndrome at the 2026 American Academy of Neurology Annual Meeting being held April 18 – 22 in Chicago, IL.

The ARGUS trial is currently enrolling, and more information about the trial can be found at argustrial.com.

Poster presentation details are listed below:

Abstract Title:		ARGUS: A Study of EPX-100 (Clemizole Hydrochloride) as Adjunctive Therapy in Participants with Dravet Syndrome (DS): Preliminary Results from the Open-label Extension Phase

Poster #:		P10.010

Date/Time:		Wednesday, April 22, 2026, from 8:00 AM – 9:00 AM CT

About Clemizole Hydrochloride (EPX-100)

EPX-100, clemizole hydrochloride, is under development for the treatment of Dravet syndrome (DS) and Lennox-Gastaut syndrome (LGS). EPX-100 acts by targeting central 5-hydroxytryptamine receptors to modulate serotonin signaling. The drug candidate is administered orally twice a day in a liquid formulation and has been developed based on a proprietary phenotype-based zebrafish drug screening platform. DS is caused by a loss of function mutation in the SCN1A gene, and scn1 mutant zebrafish replicate the genetic etiology and phenotype observed in the majority of individuals with DS. The scn1Lab mutant zebrafish model that expresses voltage gated sodium channels has been used for high-throughput screening of compounds that modulate Nav1.1 in the central nervous system.

About Dravet Syndrome

Dravet syndrome (DS) is a severe and progressive epileptic encephalopathy that begins in infancy and causes significant impact on patient functioning. DS begins in the first year of life and is characterized by high seizure frequency and severity, intellectual disability, and a risk of sudden unexpected death in epilepsy. Approximately 85% of Dravet syndrome cases are caused by de novo loss-of-function (LOF) mutations in SCN1A gene, which codes for a voltage-gated sodium channel. DS has an estimated incidence rate of 1:15,700.

About Harmony Biosciences

Harmony Biosciences is a pharmaceutical company dedicated to developing and commercializing innovative therapies for patients with rare neurological diseases who have unmet medical needs. Driven by novel science, visionary thinking, and a commitment to those who feel overlooked, Harmony Biosciences is nurturing a future full of therapeutic possibilities that may enable patients with rare neurological diseases to truly thrive. Established by Paragon Biosciences, LLC, in 2017 and headquartered in Plymouth Meeting, Pa., we believe that when empathy and innovation meet, a better future can begin; a vision evident in the therapeutic innovations we advance, the culture we cultivate, and the community programs we foster. For more information, please visit www.harmonybiosciences.com.

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Harmony Biosciences Investor Contact:

Brennan Doyle

484-566-3685

bdoyle@harmonybiosciences.com

Harmony Biosciences Media Contact:

Cate McCanless

202-641-6086

cmccanless@harmonybiosciences.com

Harmony Biosciences to Present Open-Label Extension Data From Phase 3 ARGUS Trial at the 2026 American Academy of Neurology Annual Meeting