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Elsunersen

Phase 3

Epileptic Encephalopathy | Small molecule | Neurology |Praxis Precision Medicines, Inc.|Last Updated: Aug 3, 2026

Target and mechanism

Molecular targetSCN2A
Target class-Sen (Aso)
ModalitySmall molecule

Also known as PRAX-222 - Initial Dose, PRAX-222- Initial Dose, PRAX-222 - Initial Ascending Doses, PRAX-222- Initial Ascending Doses, PRAX-222 - Optional Ascending Doses, PRAX-222- Optional Ascending Doses, PRAX-222 - Fixed Doses, PRAX-222- Fixed Doses

Success Probability

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Market & Valuation

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Trial Design

CONTROLLEDDMC
Total Trials1
Total Enrollment40

FDA Designations

BREAKTHROUGH_THERAPYORPHAN_DRUGRARE_PEDIATRIC_DISEASE

Clinical trial landscape

Elsunersen · 2 trials · 4 indications

Phase 3 1Phase 1 1
NCT07019922A Clinical Trial of Elsunersen in Pediatric SCN2A-DEE to Assess Efficacy and SafetyEpileptic Encephalopathy
RECRUITING40 Analytics
PHASE3RECRUITING
A Clinical Trial of Elsunersen in Pediatric SCN2A-DEE to Assess Efficacy and Safety
Epileptic EncephalopathyUnlock trial analytics

Study Endpoints

Primary Endpoints

To assess the efficacy of elsunersen on seizure frequency in participants with early-onset SCN2A DEE
24 weeks

Median percent change in monthly (28 days) motor seizure frequency from baseline to treatment after 24 weeks

Number of participants with treatment-emergent adverse events (Preliminary Safety, Dose Escalation)
Screening (-8 weeks) through up to 92 weeks

The number of participants with treatment-emergent adverse events will be reported by severity and preferred term.

Seizure frequency (Confirmatory Phase)
36 to 40 weeks

Seizure frequency will be captured by a seizure diary and outcomes will be measured by summing the seizure frequency over a 28-day time period following the 6th dose administration in the confirmatory phase.

Secondary Endpoints

To assess secondary efficacy outcomes of elsunersen in participants with early-onset SCN2A DEE
24 weeks
CGI-S change from baseline
24 weeks
CGI subdomain scores at each postdose time point
24 weeks
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Study Design & Arms

AllocationNON_RANDOMIZED
MaskingNONE
ModelSEQUENTIAL
PurposeTREATMENT

Treatment Arms

ArmTypeDescription
Cohort 1 Arm 1: Open-Label Treatment PeriodEXPERIMENTALOpen-label elsunersen
Cohort 2: Open-Label Treatment PeriodEXPERIMENTALOpen-label elsunersen
Cohort 3: Open-Label Treatment PeriodEXPERIMENTALOpen-label elsunersen
Preliminary SafetyEXPERIMENTALOpen-label PRAX-222
Dose Escalation - PRAX-222EXPERIMENTALInitial dose escalation consisting of double-blind ascending doses of PRAX-222
Dose Escalation - PlaceboPLACEBO_COMPARATORDouble-blind placebo procedure
Optional Dose Escalation - PRAX-222EXPERIMENTALOptional dose escalation consisting of double-blind ascending doses of PRAX-222
Optional Dose Escalation - PlaceboPLACEBO_COMPARATORDouble-blind placebo procedure
Confirmatory Dosing - PRAX-222EXPERIMENTALDouble-blind fixed-dose PRAX-222
Confirmatory Dosing - PlaceboEXPERIMENTALDouble-blind placebo procedure
Open-label PRAX-222EXPERIMENTALOpen-label PRAX-222

Interventions

NameTypeDescription
1mg elsunersenDRUG24 weeks every 4 weeks intrathecally
0.5mg elsunersenDRUG24 weeks every 4 weeks intrathecally
PRAX-222 - Initial DoseDRUGPRAX-222
PRAX-222 - Initial Ascending DosesDRUGAscending doses of PRAX-222
PRAX-222 - Optional Ascending DosesDRUGEscalation of PRAX-222 dose(s)
PRAX-222 - Fixed DosesDRUGFixed-dose(s) of PRAX-222 not to exceed the maximum tolerated dose of PRAX-222
PlaceboPROCEDUREPlacebo procedure
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Eligibility Criteria

Age Range1 Day to 18 Years
SexALL
Healthy VolunteersNo
Study Sites10

Inclusion Criteria: * Has a documented Gain of Function SCN2A variant confirmed through genetic testing. * Has onset of seizures prior to 3 months of age. * Seizure frequency of 4 or more countable motor seizures per 28-day during the Baseline Observation Period. Exclusion Criteria: * Has any cli...

Countries:United StatesBrazilGermanyItaly
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Recent Changes (Last 90 Days)

MEDIUMAug 3, 2026NCT05737784Status: RECRUITING → ACTIVE_NOT_RECRUITING
MEDIUMAug 3, 2026NCT07019922primaryCompletionDate: changed
MEDIUMAug 3, 2026NCT07019922primaryCompletionDate: changed
MEDIUMAug 3, 2026NCT05737784Status: RECRUITING → ACTIVE_NOT_RECRUITING

Frequently asked questions about Elsunersen

What is elsunersen used for?

Elsunersen is an investigational small molecule being developed for epileptic encephalopathy, specifically SCN2A encephalopathy, a form of developmental and epileptic encephalopathy. It is currently in Phase 3 clinical development and has not been approved by the FDA.

What does elsunersen target?

Elsunersen targets the SCN2A gene, which encodes a sodium channel subunit. As an antisense oligonucleotide (ASO), it is designed to modulate SCN2A expression. It is being studied in patients with SCN2A-related epileptic encephalopathy.

Who is developing elsunersen?

Elsunersen is being developed by Praxis Precision Medicines, Inc., a biopharmaceutical company traded on NASDAQ under the ticker PRAX. The company is conducting a Phase 3 clinical trial of elsunersen in pediatric patients with SCN2A developmental and epileptic encephalopathy.

What phase is elsunersen in?

Elsunersen is currently in Phase 3 clinical development. It is an investigational drug and has not received FDA approval. The drug has been granted Breakthrough Therapy, Orphan Drug, and Rare Pediatric Disease designations by the FDA for its intended indication.

What clinical trials is elsunersen in?

Elsunersen is being evaluated in a Phase 3 clinical trial with the identifier NCT07019922. This trial is recruiting an estimated 40 participants across the United States, Brazil, Germany, and Italy. The study is open to pediatric patients as young as 1 day old with SCN2A encephalopathy.

Is elsunersen the same as 1mg elsunersen?

Yes, elsunersen is also known as 1mg elsunersen. This alternative name may be used in certain contexts, but both refer to the same investigational drug being developed by Praxis Precision Medicines for SCN2A-related epileptic encephalopathy.