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Clemizole

Phase 3

Dravet Syndrome | Small molecule | Neurology |Harmony Biosciences Holdings, Inc.|Last Updated: Apr 15, 2026

Target and mechanism

Molecular target5-HT2
ModalitySmall molecule

Also known as Clemizole HCl

Success Probability

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Market & Valuation

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Trial Design

RandomizedDouble-BlindPLACEBO_CONTROLLEDDMCBiomarker
Total Trials1
Total Enrollment150

FDA Designations

No designations recorded

Clinical trial landscape

Clemizole · 2 trials · 2 indications

Phase 3 2
NCT05066217An Efficacy and Safety Study of Clemizole HCl in Patients With Lennox-Gastaut SyndromeLennox Gastaut Syndrome
RECRUITING260 Analytics
NCT04462770A Study of EPX-100 (Clemizole Hydrochloride) in Participants With Dravet SyndromeDravet Syndrome
RECRUITING150 Analytics
PHASE3RECRUITING
An Efficacy and Safety Study of Clemizole HCl in Patients With Lennox-Gastaut Syndrome
Lennox Gastaut SyndromeUnlock trial analytics
PHASE3RECRUITING
A Study of EPX-100 (Clemizole Hydrochloride) in Participants With Dravet Syndrome
Dravet SyndromeUnlock trial analytics

Study Endpoints

Primary Endpoints

Percent Change in CMMS-28
From Baseline Period up to 16 weeks

Percent change in CMMS-28 from the Baseline Period through the end of the DB Period

Percent Change in Countable Motor Seizures Per 28 Days (CMS-28) in the Titration Plus Maintenance Periods Relative to Baseline
From Baseline Period (Day 1) up to 16 weeks

Percent change in CMS-28 from the Baseline Period through the end of the DB period.

European Union: Percent Change in Countable Motor Seizures Per 28 Days in the Maintenance Period Relative to Baseline
From maintenance period Baseline (Day 29) up to Day 85

Percent change in CMS-28 from the Baseline Period through the end of the maintenance period.

Secondary Endpoints

Proportion of Participants with ≥50% Reduction in CMMS-28
From Baseline Period up to 16 weeks
Percent Change in CMMS-28 Seizure-free Days
From Baseline Period up to 16 weeks
Clinical Global Impression of Change (CGI-C) Score
Week 16
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Study Design & Arms

AllocationRANDOMIZED
MaskingTRIPLE
ModelPARALLEL
PurposeTREATMENT

Treatment Arms

ArmTypeDescription
PlaceboPLACEBO_COMPARATORParticipants will receive their first dose of study drug following randomization.
Double-blind clemizole HClEXPERIMENTALParticipants will receive their first dose of study drug following randomization.
Open-label clemizole HClEXPERIMENTALEligible participants who complete the DB Period will have the option to continue in the OLE Period, during which they will receive clemizole HCl for up to 3 years.

Interventions

NameTypeDescription
Clemizole HClDRUGClemizole HCl will be administered as an oral solution.
PlaceboDRUGPlacebo will be administered as an oral solution.
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Eligibility Criteria

Age Range2 Years to 55 Years
SexALL
Healthy VolunteersNo
Study Sites20

Key Inclusion Criteria: 1. Males or females, ages ≥2 to ≤55 years, at the time of Screening. 2. Participant/parent/legal authorized representative (LAR) willing and able to give written informed consent/assent. 3. Diagnosis of LGS, including: * Evidence of at least one type of countable major m...

Countries:United StatesCanadaGeorgiaHungaryPolandRomaniaSpainUnited Kingdom
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Frequently asked questions about Clemizole

What is Clemizole used for?

Clemizole is an investigational small molecule being developed for the treatment of Dravet Syndrome and Lennox Gastaut Syndrome, both rare forms of epilepsy. It is currently in Phase 3 clinical development and has not been approved by regulatory authorities.

What does Clemizole target?

Clemizole targets the 5-HT2 receptor, a subtype of serotonin receptor. By modulating this target, the drug is being studied for its potential to reduce seizure frequency in patients with Dravet Syndrome and Lennox Gastaut Syndrome.

Who makes Clemizole?

Clemizole is being developed by Harmony Biosciences Holdings, Inc., a biopharmaceutical company traded on the NASDAQ under the ticker symbol HRMY. The company is conducting Phase 3 clinical trials to evaluate the drug's safety and efficacy.

What phase is Clemizole in?

Clemizole is currently in Phase 3 clinical development. It is an investigational drug and has not been approved by the FDA or any other regulatory agency. Two Phase 3 trials are actively recruiting patients to assess its efficacy and safety.

What clinical trials is Clemizole in?

Clemizole is being studied in two Phase 3 trials. NCT05066217 is evaluating the drug in patients with Lennox Gastaut Syndrome, enrolling 260 participants in the United States. NCT04462770 is studying Clemizole in Dravet Syndrome, with 150 participants across multiple countries including the US, Canada, and several European nations.

Is Clemizole the same as Clemizole HCl?

Yes, Clemizole HCl is the hydrochloride salt form of Clemizole. Clinical trials use the HCl formulation, and the terms are often used interchangeably when referring to the investigational drug being developed by Harmony Biosciences.