SCN2A EncephalopathyPhase 2/3EMBOLDNCT05818553
A Clinical Trial of PRAX-562 in Subjects With Developmental and Epileptic Encephalopathies (DEE)
A Phase 2/3 study testing PRAX-562 in people with SCN2A Encephalopathy and SCN8A Encephalopathy, run by Praxis Precision Medicines at 8 sites in 4 countries.
Trial summary
A Clinical Trial of PRAX-562 in Subjects With Developmental and Epileptic Encephalopathies (DEE) Read more about this study
- Who is it for?
- Ages 1 year to 18 years
- Conditions the study is for
- SCN2A Encephalopathy, SCN8A Encephalopathy
- What is being tested?
- PRAX-562
- Type of treatment
- Pill or oral medicine
- Could I receive a placebo?
- No, everyone receives an active treatment
- How many people
- 77 participants
- Where
- 8 sitesin 4 countries
- Study dates
- 2 Aug 2023to 1 Mar 2027
- Phase
- Phase 2/3
- Are there results?
- Not yet: the study is under way
Key requirements
Who can take part, as listed by the sponsor. Only the study team can confirm whether you are eligible, so take this list to your doctor.
- Ages 1 year to 18 years
- All sexes
- No healthy volunteers
- Child, Adult
Who may be able to join
- Has a documented variant in SCN2A with onset of seizures occurring in the first 3 months of life or has a diagnosis of SCN8A-DEE supported by both clinical and genetic findings.
- Has a seizure frequency as follows:
- At least 8 countable motor seizures in the 4 weeks immediately prior to Screening as reported by the parent/legal guardian or in the opinion of the investigator as documented in medical notes.
- AND o At least 8 countable motor seizures during the 28 day Baseline Observation Period (during which seizure frequency is recorded in a daily seizure diary).
- Additional inclusion criteria apply and will be assessed by the study team.
Who cannot join
- Has any clinically significant or known pathogenic or likely pathogenic genetic variant other than in SCN2A and SCN8A or a genetic variant that may explain or contribute to the participant's epilepsy and/or developmental disorder.
- Has a documented, functionally characterized loss-of-function (LoF) missense variant or a presumed LoF variant (nonsense or frameshift variant) based on genetic testing and/or clinical evidence that prior exposure to a sodium channel blocker (SCB) medication worsened seizures.
- Has 2 or more episodes of convulsive status epilepticus requiring hospitalization and intubation in the 6 months prior to Screening.
- Additional exclusion criteria apply and will be assessed by the study team.
Trial locations and contacts
8 sites in 4 countries.
8 sites in 4 countries
United States4 sites
Praxis Research Site
Atlanta, Georgia, 30329
Praxis Research Site
Chicago, Illinois, 60611
Praxis Research Site
Hackensack, New Jersey, 07601
Praxis Research Site
Minneapolis, Minnesota, 55113
United Kingdom2 sites
Praxis Research Site
Glasgow, G51 4TF
Praxis Research Site
London, WC1N 3BH
About this study
Official title: A Phase 2,Double-Blind,Randomized Clinical Trial to Explore the Safety,Tolerability,Efficacy, and Pharmacokinetics of PRAX-562 in Pediatric Participants With Developmental and Epileptic Encephalopathies Followed by Open-Label Extension(OLE)
A Clinical Trial of PRAX-562 in Subjects With Developmental and Epileptic Encephalopathies (DEE)
Read the detailed description
A Phase 2, double-blind, randomized clinical trial to evaluate the safety and tolerability of PRAX 562 in pediatric participants with SCN2A- and SCN8A- DEEs.
- Conditions
- SCN2A Encephalopathy, SCN8A Encephalopathy
- Being tested
- PRAX-562
- Keywords
- Pediatric epilepsy, NaV1.2 Voltage-Gated Sodium Channel, SCN2A variant, SCN8A variant, Developmental and epileptic encephalopathy
What participants receive
What participants receive. In a randomised study each person is assigned to one group by chance.
PRAX-562Drug
Once daily oral or G-tube treatment.
| Study group | Role | What they receive |
|---|---|---|
| Part A: Randomized, Double-Blind 0.5mg/kg/day PRAX-562 or PRAX-562/Placebo | Experimental | Eligible participants from each cohort will be randomized in a 1:1 ratio to either 0.5 milligrams/kilograms/day (mg/kg/day) PRAX-562 for 16 weeks (PRAX-562 arm) or 0.5 mg/kg/day PRAX-562 for 12 weeks and matching placebo for 4 weeks (PRAX-562/placebo arm) administered orally or via gastrostomy tube (G-tube). Receives: Drug: PRAX-562 |
| Part B: Open-Label Extension Treatment 0.5mg/kg/day PRAX-562 | Experimental | Eligible participants will receive 0.5mg/kg/day administered orally or via G-tube for up to 144 weeks. Receives: Drug: PRAX-562 |
| Part A: Randomized, Double-Blind 1.0 mg/kg/day PRAX-562 or PRAX-562/Placebo | Experimental | Eligible participants from each cohort will be randomized in a 1:1 ratio to either 1.0 milligrams/kilograms/day (mg/kg/day) PRAX-562 for 16 weeks (PRAX-562 arm) or 1.0 mg/kg/day PRAX-562 for 12 weeks and matching placebo for 4 weeks (PRAX-562/placebo arm) administered orally or via gastrostomy tube (G-tube). Receives: Drug: PRAX-562 |
| Open-Label Extension Treatment 1.0 mg/kg/day PRAX-562 | Experimental | Eligible participants will receive 1.0 mg/kg/day administered orally or via G-tube for up to 144 weeks. Receives: Drug: PRAX-562 |
What is being measured
The primary outcome is the main question the study is designed to answer.
PART A (Cohorts 1 and 2) RDB: To evaluate the safety and tolerability of PRAX 562 in pediatric participants with SCN2A- and SCN8A- DEEs
Changes from baseline in monthly (28-day) motor seizure frequency
Measured: 16 weeks
PART B (Cohorts 1 and 2) OLE: To evaluate the long-term safety and tolerability of PRAX-562 in pediatric participants with DEEs
Incidence and severity of TEAEs
Measured: 48 weeks
Secondary outcomes (5)
PART A (Cohorts 1 and 2) RDB: To assess the effect of PRAX-562 on the frequency of countable motor seizures in pediatric participants with DEEs
Changes from baseline in monthly (28-day) motor seizure frequency
Measured: 16 weeks
Plasma concentrations of PRAX-562
Sparse pharmacokinetic (PK) sampling will be used to calculate mean concentrations at baseline, and at Weeks 2, 4, 6, 8,10, 12 and 16.
Measured: 16 weeks
Seizure Frequency (OLE Extension)
Efficacy assessments (seizure diary) will be collected daily and reviewed at timepoints Day 1, Week 16, Week 32, and Week 48.
Measured: 48 weeks
To assess the effect of PRAX-562 on the frequency of countable motor seizures in pediatric participants with DEEs
Changes from baseline in monthly (28-day) motor seizure frequency
Measured: 16 weeks
Incidence of Treatment-Emergent Adverse Events (TEAEs) [Safety and Tolerability])
The number of participants with treatment-emergent adverse events will be reported by severity and preferred term.
Measured: 16 weeks
Timeline
From the start of the study to its completion; the mark is today. Estimated dates are the sponsor’s plan.
- First posted19 Apr 2023
- Study start2 Aug 2023
- Primary completion12 Nov 2025
- Study completion1 Mar 2027 (estimated)
Resources
- Official record on ClinicalTrials.govThe registry entry this page is built from, with its full change history.
- Other trials for SCN2A EncephalopathyStudies of the same condition, open and under way.
- What the trial phases meanHow a treatment moves from first tests in people to approval.
More details
For doctors and researchers: how the study is designed, who runs it, and its registry IDs.
Study design
- Study type
- Interventional
- Phase
- Phase 2/3
- Primary purpose
- Treatment
- Allocation
- Randomised
- Intervention model
- Parallel groups
- Model description
- Parallel group
- Masking
- Triple blind
- Who is masked
- Participant, Care provider, Investigator
- Enrolment
- 77 participants (estimated)
Sponsor and investigators
- Lead sponsor
- Praxis Precision Medicines
- Sponsor type
- Industry (pharma, biotech, devices)
- Responsible party
- Sponsor
- Investigators
- Medical Director, Study director, Praxis Precision Medicines
IDs, dates and publications
- ClinicalTrials.gov ID
- NCT05818553
- Sponsor's protocol ID
- PRAX-562-221
- Acronym
- EMBOLD
- Status last verified
- Jan 2025
- First submitted
- 17 Mar 2023
- Last updated
- 29 Jan 2026
- Results posted
- No
- Data monitoring committee
- No
- FDA-regulated drug
- Yes
- FDA-regulated device
- No
Study at a glance
From the registry record, last updated by the sponsor on 29 Jan 2026. Recruitment status is as the sponsor reported it: confirm with the study team.
- Official title
- A Phase 2,Double-Blind,Randomized Clinical Trial to Explore the Safety,Tolerability,Efficacy, and Pharmacokinetics of PRAX-562 in Pediatric Participants With Developmental and Epileptic Encephalopathies Followed by Open-Label Extension(OLE)
- ClinicalTrials.gov ID
- NCT05818553
- Acronym / sponsor ID
- EMBOLD / PRAX-562-221
- Conditions
- SCN2A Encephalopathy, SCN8A Encephalopathy
- Keywords
- Pediatric epilepsy, NaV1.2 Voltage-Gated Sodium Channel, SCN2A variant, SCN8A variant, Developmental and epileptic encephalopathy
- Phase
- Phase 2/3
- Study type
- Interventional
- Recruitment status
- Active, not recruiting
- Enrolment
- 77 participants (estimated)
- Lead sponsor
- Praxis Precision MedicinesIndustry (pharma, biotech, devices)
- Study start
- 2 Aug 2023 (actual)
- Primary completion
- 12 Nov 2025 (actual)
- Study completion
- 1 Mar 2027 (estimated)
- First posted
- 19 Apr 2023 (actual)
- Results
- Not posted in the source record
Clinical summary
The research question as the sponsor registered it. This describes what the study plans to test, not what it found.
A Clinical Trial of PRAX-562 in Subjects With Developmental and Epileptic Encephalopathies (DEE)
Detailed description
A Phase 2, double-blind, randomized clinical trial to evaluate the safety and tolerability of PRAX 562 in pediatric participants with SCN2A- and SCN8A- DEEs.
Study design
- Primary purpose
- Treatment
- Allocation
- Randomised
- Intervention model
- Parallel groups
- Masking
- Triple blind (participant, care provider, investigator)
- Number of arms
- 4
- Model description
- Parallel group
| Arm | Type | Receives |
|---|---|---|
| Part A: Randomized, Double-Blind 0.5mg/kg/day PRAX-562 or PRAX-562/Placebo | Experimental | Drug: PRAX-562Eligible participants from each cohort will be randomized in a 1:1 ratio to either 0.5 milligrams/kilograms/day (mg/kg/day) PRAX-562 for 16 weeks (PRAX-562 arm) or 0.5 mg/kg/day PRAX-562 for 12 weeks and matching placebo for 4 weeks (PRAX-562/placebo arm) administered orally or via gastrostomy tube (G-tube). |
| Part B: Open-Label Extension Treatment 0.5mg/kg/day PRAX-562 | Experimental | Drug: PRAX-562Eligible participants will receive 0.5mg/kg/day administered orally or via G-tube for up to 144 weeks. |
| Part A: Randomized, Double-Blind 1.0 mg/kg/day PRAX-562 or PRAX-562/Placebo | Experimental | Drug: PRAX-562Eligible participants from each cohort will be randomized in a 1:1 ratio to either 1.0 milligrams/kilograms/day (mg/kg/day) PRAX-562 for 16 weeks (PRAX-562 arm) or 1.0 mg/kg/day PRAX-562 for 12 weeks and matching placebo for 4 weeks (PRAX-562/placebo arm) administered orally or via gastrostomy tube (G-tube). |
| Open-Label Extension Treatment 1.0 mg/kg/day PRAX-562 | Experimental | Drug: PRAX-562Eligible participants will receive 1.0 mg/kg/day administered orally or via G-tube for up to 144 weeks. |
Who may qualify
- Ages
- 1 year to 18 years
- Sex
- All
- Healthy volunteers
- Not accepted
- Age groups
- Child, Adult
Key inclusion criteria (5 listed)
- Has a documented variant in SCN2A with onset of seizures occurring in the first 3 months of life or has a diagnosis of SCN8A-DEE supported by both clinical and genetic findings.
- Has a seizure frequency as follows:
- AND o At least 8 countable motor seizures during the 28 day Baseline Observation Period (during which seizure frequency is recorded in a daily seizure diary).
- Additional inclusion criteria apply and will be assessed by the study team.
Key exclusion criteria (4 listed)
- Has any clinically significant or known pathogenic or likely pathogenic genetic variant other than in SCN2A and SCN8A or a genetic variant that may explain or contribute to the participant's epilepsy and/or developmental disorder.
- Has a documented, functionally characterized loss-of-function (LoF) missense variant or a presumed LoF variant (nonsense or frameshift variant) based on genetic testing and/or clinical evidence that prior exposure to a sodium channel blocker (SCB) medication worsened seizures.
- Has 2 or more episodes of convulsive status epilepticus requiring hospitalization and intubation in the 6 months prior to Screening.
- Additional exclusion criteria apply and will be assessed by the study team.
Eligibility is decided by the study team after screening; this overview does not establish that a patient qualifies. Full inclusion and exclusion criteria.
Interventions
| Intervention | Type | Arms |
|---|---|---|
| PRAX-562Once daily oral or G-tube treatment. | Drug | Open-Label Extension Treatment 1.0 mg/kg/day PRAX-562, Part A: Randomized, Double-Blind 0.5mg/kg/day PRAX-562 or PRAX-562/Placebo, Part A: Randomized, Double-Blind 1.0 mg/kg/day PRAX-562 or PRAX-562/Placebo, Part B: Open-Label Extension Treatment 0.5mg/kg/day PRAX-562 |
Primary outcome
PART A (Cohorts 1 and 2) RDB: To evaluate the safety and tolerability of PRAX 562 in pediatric participants with SCN2A- and SCN8A- DEEs
Time frame: 16 weeks
Changes from baseline in monthly (28-day) motor seizure frequency
PART B (Cohorts 1 and 2) OLE: To evaluate the long-term safety and tolerability of PRAX-562 in pediatric participants with DEEs
Time frame: 48 weeks
Incidence and severity of TEAEs
5 secondary outcomes
PART A (Cohorts 1 and 2) RDB: To assess the effect of PRAX-562 on the frequency of countable motor seizures in pediatric participants with DEEs
Time frame: 16 weeks
Plasma concentrations of PRAX-562
Time frame: 16 weeks
Seizure Frequency (OLE Extension)
Time frame: 48 weeks
To assess the effect of PRAX-562 on the frequency of countable motor seizures in pediatric participants with DEEs
Time frame: 16 weeks
Incidence of Treatment-Emergent Adverse Events (TEAEs) [Safety and Tolerability])
Time frame: 16 weeks
Results and safety
This study is still under way. Results are not available in the source record yet.
Research links
- Official record on ClinicalTrials.govLast updated by the sponsor 29 Jan 2026.
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RecruitingPhase 3
A Clinical Trial of Elsunersen in Pediatric SCN2A-DEE to Assess Efficacy and Safety
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Referral and contact
AzTrials does not enrol participants or take referrals. Contact the study team or a site listed below; they decide who can take part. This study is not recruiting at the moment.
Medical Director study director
Praxis Precision Medicines
8 sites in 4 countries: see every site and its status.
Questions about this trial
What is this clinical trial studying?
A Phase 2/3 study testing PRAX-562 in people with SCN2A Encephalopathy and SCN8A Encephalopathy, run by Praxis Precision Medicines at 8 sites in 4 countries.
The full registered description is in the About this study section and the official record.
Who may be eligible to take part?
The sponsor lists 5 inclusion and 4 exclusion criteria. Eligibility is decided by the study team after screening, so read the full criteria and contact a listed site.
Is this clinical trial currently recruiting?
The record says: under way, not looking for participants, as of the sponsor's last update on 29 Jan 2026. Status can change between updates, so confirm with the study contact before making plans.
Where is the study taking place?
The record lists 8 sites in United States, United Kingdom, Israel, Spain. Whether a site is taking part right now should be confirmed with that site. See every site.
What are the possible benefits and risks?
They depend on the study and the treatment, and no study can promise a benefit. The study team explains the known risks during informed consent, before anyone joins; the record itself does not list them.
What does this combined phase mean?
Phase 2 studies give the treatment to a larger group to see whether it has the intended effect and to keep checking safety.
Phase 3 studies compare the treatment with the current standard treatment or a placebo in a large group, to confirm how well it works and watch for side effects.
Not every study follows the same path, and some studies (observational studies, device studies) have no phase.
Are results available for this study?
This study is still under way. Results are not available in the source record yet.
How can a doctor refer a patient or contact the research team?
The record lists no contact. The official record names the sponsor, who can be asked directly. AzTrials does not enrol participants or take referrals.
What does the primary outcome measure?
PART A (Cohorts 1 and 2) RDB: To evaluate the safety and tolerability of PRAX 562 in pediatric participants with SCN2A- and SCN8A- DEEs (time frame: 16 weeks). The study lists 2 primary outcomes in all. It is what the study was designed to measure, not a finding.
Where can I read the original study information?
Does a listing mean the treatment is approved or proven to work?
No. A listing means the study is registered. It does not show that the treatment is safe, works, or is approved by a regulator.
How often is this information updated?
AzTrials copies changed records from ClinicalTrials.gov every night and reloads the whole registry every week. The sponsor last updated this record on 29 Jan 2026.