This template was built with Webflow's free Prospero UI Kit. Learn more
On June 22, 2026, the U.S. Food and Drug Administration (FDA) granted Breakthrough Therapy Designation to Elsunersen (PRAX-222) for the treatment of seizures in children with SCN2A developmental and epileptic encephalopathy (DEE) caused by gain-of-function variants. Elsunersen is an antisense oligonucleotide (ASO), a type of precision therapy designed to target the genetic cause of the condition. No other therapy for SCN2A-DEE has received this designation.
This post helps explain the science, the trial results, and the road ahead. Whether your child has a confirmed gain-of-function SCN2A variant or you are still in the process of understanding your child's diagnosis, we hope this will help you make sense of what happened and why it matters.
An antisense oligonucleotide is a small, synthetic piece of genetic material. It is designed to attach to a specific messenger RNA (mRNA) inside cells. Think of mRNA as an instruction sheet. Your cells read it to build proteins. An ASO binds to that instruction sheet and blocks it, which reduces the amount of a specific protein the cell produces.
ASOs do not change DNA. They work at the RNA level, adjusting how the body reads and uses the instructions encoded in a gene. This is a temporary effect. Repeated doses maintain the therapeutic benefit over time. In the case of Elsunersen the therapy is delivered directly into the central nervous system through an intrathecal injection (a procedure that places medication into the fluid surrounding the spinal cord). This route allows the ASO to reach the brain where Nav1.2 sodium channels are most active.
The FDA has already approved ASO therapies for other genetic conditions, including spinal muscular atrophy and Duchenne muscular dystrophy. Elsunersen applies this same class of technology to SCN2A.
The SCN2A gene provides instructions for making the Nav1.2 sodium channel. This protein helps brain cells send electrical signals. In children with gain-of-function SCN2A variants, the gene is overactive. It produces too much sodium channel activity, which can cause seizures that begin in infancy and significantly affect development.
Current treatments for these seizures manage symptoms. They do not address the genetic cause. Elsunersen is designed to go further. By reducing SCN2A gene expression at the RNA level, it aims to lower sodium channel activity back toward a typical range. This is what makes it a precision therapy: it targets the specific mechanism driving the condition. Preclinical research published in JCI Insight demonstrated that an ASO targeting Scn2a in a mouse model of gain-of-function DEE effectively suppressed seizures and extended lifespan, with treated mice performing similarly to healthy controls across motor and behavioral tests.
FDA Breakthrough Therapy Designation is a formal recognition that a therapy may offer a meaningful advantage over existing treatments for a serious condition. The FDA grants it when early clinical data suggests the therapy could substantially improve patient outcomes on at least one clinically significant measure.
This designation does not mean the therapy is approved. It does not mean it is available to patients today. What it changes is the speed and structure of the development process.
Specifically, it provides more frequent and intensive guidance from the FDA during clinical development, involvement of senior FDA leadership in the review process, and eligibility for rolling review of application materials and priority review.
For families, the practical takeaway is this: the FDA reviewed the early clinical data for Elsunersen and determined the evidence is strong enough to accelerate the path toward a potential approval decision.
Elsunersen now holds three FDA designations: Breakthrough Therapy, Orphan Drug, and Rare Pediatric Disease. It also holds Orphan Drug and PRIME designations from the European Medicines Agency (EMA).
The Breakthrough Therapy Designation was based on results from the EMBRAVE Part A trial, a randomized, sham-controlled Phase 1/2 study. Praxis Precision Medicines reported topline results in April 2026.
EMBRAVE Part A enrolled nine children between the ages of 2 and 12 with early-seizure-onset SCN2A-DEE caused by gain-of-function variants. Patients were randomized 3:1 to receive either Elsunersen or a sham procedure every four weeks for 24 weeks, followed by an open-label extension.
According to data reported by Praxis Precision Medicines:
These benefits were sustained during the open-label extension for up to one year.
The trial also showed signals beyond seizure control. According to Praxis, 100% of patients treated with Elsunersen showed improvement in at least one additional area: sleep, motor function, muscle tone, attention, or neuropsychomotor development. None of the sham-treated patients showed these improvements.
The safety profile was notable. No treatment-related serious adverse events were reported. No patients discontinued treatment. No signals of neuroinflammation were observed at doses up to 8 mg through eight months of the open-label extension.
For a broader view of where SCN2A research stands today, including other therapeutic approaches under development, visit the Foundation's research page.
The next major milestone is EMBRAVE3, the pivotal registrational study for Elsunersen . In December 2025, Praxis and the FDA agreed to convert this trial to a single-arm, baseline-controlled design. That means every child enrolled will receive Elsunersen from day one. There is no placebo arm.
The study is enrolling approximately 30 patients. The primary endpoint measures the change from baseline in countable motor seizures over 24 weeks, followed by an open-label extension. Praxis reported in its Q1 2026 corporate update that enrollment is progressing, with topline results expected in 2027.
Separately, clinical updates from an Emergency Use Program for Elsunersen were also presented at the 2026 American Academy of Neurology (AAN) meeting. According to Praxis, data from six patients treated globally through this program showed durable seizure reduction and meaningful quality-of-life improvements, with more than 100 doses administered to date. These real-world treatment experiences provide additional safety and efficacy signals as EMBRAVE3 enrollment continues.
A single-arm design compares each child's seizure frequency before treatment to their seizure frequency during treatment. The FDA agreed to this streamlined approach because of the rarity of the condition and the strength of the EMBRAVE Part A data. Families interested in the EMBRAVE3 study can learn more at embravestudy.com or speak with their child's neurologist about potential eligibility.
Elsunersen is specifically designed for gain-of-function SCN2A variants. It works by reducing SCN2A gene expression. For children with loss-of-function variants, where the gene is already underactive, this approach would not be appropriate. Always consult your child's medical team about whether a therapy is relevant to your child's specific variant. To learn more about what an SCN2A mutation is and how variant types differ, visit the Foundation's family guide.
The EMBRAVE Part A study was small. Nine patients participated in the randomized portion. The results are encouraging, but larger studies are needed. EMBRAVE3 is designed to provide that confirmation.
Timelines are not guaranteed. The Breakthrough Therapy Designation accelerates the development process. It does not set a fixed approval date. Enrollment pace, data analysis, and regulatory review all affect the timeline.
What is an ASO therapy for SCN2A?
An antisense oligonucleotide (ASO) is a small synthetic molecule designed to reduce the activity of a specific gene. Elsunersen targets the SCN2A gene to lower sodium channel activity in children with gain-of-function variants that cause seizures and developmental challenges.
What does FDA Breakthrough Therapy Designation mean?
It means the FDA has reviewed early clinical data and determined the therapy may offer a substantial improvement over available treatments for a serious condition. It accelerates the development process but does not mean the therapy is approved.
What were the results of the EMBRAVE trial for Elsunersen ?
In the EMBRAVE Part A study, treatment with Elsunersen was associated with a 77% sham-adjusted reduction in monthly seizures. Additional improvements were observed in sleep, motor function, and development. These results were reported by Praxis Precision Medicines in April 2026.
This content is provided for educational purposes only and is not intended as medical advice, diagnosis, or treatment. Always consult a qualified healthcare professional before making decisions about your child's care. The information in this post reflects publicly available data as of June 2026 and may not reflect the most current developments.
This work depends on your support. Sign up for the SCN2A patient registry to ensure your family's voice shapes what comes next. And please consider making a donation to help fund the research and resources that bring us all closer to treatments.
1. Praxis Precision Medicines. "Praxis Precision Medicines Receives FDA Breakthrough Therapy Designation for Elsunersen." GlobeNewsWire, June 22, 2026.
2. Praxis Precision Medicines. "Positive Results from the EMBRAVE Part A Trial of Elsunersen." April 6, 2026.
3. U.S. Food and Drug Administration. "Breakthrough Therapy." FDA.gov.
4. Li, M., et al. "Antisense oligonucleotide therapy reduces seizures and extends life span in an SCN2A gain-of-function epilepsy model." JCI Insight, 2021.
5. Praxis Precision Medicines. "Alignment with FDA on Simplified and Accelerated Registrational Pathway for Elsunersen." December 9, 2025.
6. Quilon, R., et al. "Antisense oligonucleotides as a precision therapy for developmental and epileptic encephalopathies." CNS Neuroscience & Therapeutics, 2024.
7. Praxis Precision Medicines. "Q1 2026 Corporate Update." May 7, 2026.
Share
On June 22, 2026, the U.S. Food and Drug Administration (FDA) granted Breakthrough Therapy Designation to Elsunersen (PRAX-222) for the treatment of seizures in children with SCN2A developmental and epileptic encephalopathy (DEE) caused by gain-of-function variants. Elsunersen is an antisense oligonucleotide (ASO), a type of precision therapy designed to target the genetic cause of the condition. No other therapy for SCN2A-DEE has received this designation.
This post helps explain the science, the trial results, and the road ahead. Whether your child has a confirmed gain-of-function SCN2A variant or you are still in the process of understanding your child's diagnosis, we hope this will help you make sense of what happened and why it matters.
An antisense oligonucleotide is a small, synthetic piece of genetic material. It is designed to attach to a specific messenger RNA (mRNA) inside cells. Think of mRNA as an instruction sheet. Your cells read it to build proteins. An ASO binds to that instruction sheet and blocks it, which reduces the amount of a specific protein the cell produces.
ASOs do not change DNA. They work at the RNA level, adjusting how the body reads and uses the instructions encoded in a gene. This is a temporary effect. Repeated doses maintain the therapeutic benefit over time. In the case of Elsunersen the therapy is delivered directly into the central nervous system through an intrathecal injection (a procedure that places medication into the fluid surrounding the spinal cord). This route allows the ASO to reach the brain where Nav1.2 sodium channels are most active.
The FDA has already approved ASO therapies for other genetic conditions, including spinal muscular atrophy and Duchenne muscular dystrophy. Elsunersen applies this same class of technology to SCN2A.
The SCN2A gene provides instructions for making the Nav1.2 sodium channel. This protein helps brain cells send electrical signals. In children with gain-of-function SCN2A variants, the gene is overactive. It produces too much sodium channel activity, which can cause seizures that begin in infancy and significantly affect development.
Current treatments for these seizures manage symptoms. They do not address the genetic cause. Elsunersen is designed to go further. By reducing SCN2A gene expression at the RNA level, it aims to lower sodium channel activity back toward a typical range. This is what makes it a precision therapy: it targets the specific mechanism driving the condition. Preclinical research published in JCI Insight demonstrated that an ASO targeting Scn2a in a mouse model of gain-of-function DEE effectively suppressed seizures and extended lifespan, with treated mice performing similarly to healthy controls across motor and behavioral tests.
FDA Breakthrough Therapy Designation is a formal recognition that a therapy may offer a meaningful advantage over existing treatments for a serious condition. The FDA grants it when early clinical data suggests the therapy could substantially improve patient outcomes on at least one clinically significant measure.
This designation does not mean the therapy is approved. It does not mean it is available to patients today. What it changes is the speed and structure of the development process.
Specifically, it provides more frequent and intensive guidance from the FDA during clinical development, involvement of senior FDA leadership in the review process, and eligibility for rolling review of application materials and priority review.
For families, the practical takeaway is this: the FDA reviewed the early clinical data for Elsunersen and determined the evidence is strong enough to accelerate the path toward a potential approval decision.
Elsunersen now holds three FDA designations: Breakthrough Therapy, Orphan Drug, and Rare Pediatric Disease. It also holds Orphan Drug and PRIME designations from the European Medicines Agency (EMA).
The Breakthrough Therapy Designation was based on results from the EMBRAVE Part A trial, a randomized, sham-controlled Phase 1/2 study. Praxis Precision Medicines reported topline results in April 2026.
EMBRAVE Part A enrolled nine children between the ages of 2 and 12 with early-seizure-onset SCN2A-DEE caused by gain-of-function variants. Patients were randomized 3:1 to receive either Elsunersen or a sham procedure every four weeks for 24 weeks, followed by an open-label extension.
According to data reported by Praxis Precision Medicines:
These benefits were sustained during the open-label extension for up to one year.
The trial also showed signals beyond seizure control. According to Praxis, 100% of patients treated with Elsunersen showed improvement in at least one additional area: sleep, motor function, muscle tone, attention, or neuropsychomotor development. None of the sham-treated patients showed these improvements.
The safety profile was notable. No treatment-related serious adverse events were reported. No patients discontinued treatment. No signals of neuroinflammation were observed at doses up to 8 mg through eight months of the open-label extension.
For a broader view of where SCN2A research stands today, including other therapeutic approaches under development, visit the Foundation's research page.
The next major milestone is EMBRAVE3, the pivotal registrational study for Elsunersen . In December 2025, Praxis and the FDA agreed to convert this trial to a single-arm, baseline-controlled design. That means every child enrolled will receive Elsunersen from day one. There is no placebo arm.
The study is enrolling approximately 30 patients. The primary endpoint measures the change from baseline in countable motor seizures over 24 weeks, followed by an open-label extension. Praxis reported in its Q1 2026 corporate update that enrollment is progressing, with topline results expected in 2027.
Separately, clinical updates from an Emergency Use Program for Elsunersen were also presented at the 2026 American Academy of Neurology (AAN) meeting. According to Praxis, data from six patients treated globally through this program showed durable seizure reduction and meaningful quality-of-life improvements, with more than 100 doses administered to date. These real-world treatment experiences provide additional safety and efficacy signals as EMBRAVE3 enrollment continues.
A single-arm design compares each child's seizure frequency before treatment to their seizure frequency during treatment. The FDA agreed to this streamlined approach because of the rarity of the condition and the strength of the EMBRAVE Part A data. Families interested in the EMBRAVE3 study can learn more at embravestudy.com or speak with their child's neurologist about potential eligibility.
Elsunersen is specifically designed for gain-of-function SCN2A variants. It works by reducing SCN2A gene expression. For children with loss-of-function variants, where the gene is already underactive, this approach would not be appropriate. Always consult your child's medical team about whether a therapy is relevant to your child's specific variant. To learn more about what an SCN2A mutation is and how variant types differ, visit the Foundation's family guide.
The EMBRAVE Part A study was small. Nine patients participated in the randomized portion. The results are encouraging, but larger studies are needed. EMBRAVE3 is designed to provide that confirmation.
Timelines are not guaranteed. The Breakthrough Therapy Designation accelerates the development process. It does not set a fixed approval date. Enrollment pace, data analysis, and regulatory review all affect the timeline.
What is an ASO therapy for SCN2A?
An antisense oligonucleotide (ASO) is a small synthetic molecule designed to reduce the activity of a specific gene. Elsunersen targets the SCN2A gene to lower sodium channel activity in children with gain-of-function variants that cause seizures and developmental challenges.
What does FDA Breakthrough Therapy Designation mean?
It means the FDA has reviewed early clinical data and determined the therapy may offer a substantial improvement over available treatments for a serious condition. It accelerates the development process but does not mean the therapy is approved.
What were the results of the EMBRAVE trial for Elsunersen ?
In the EMBRAVE Part A study, treatment with Elsunersen was associated with a 77% sham-adjusted reduction in monthly seizures. Additional improvements were observed in sleep, motor function, and development. These results were reported by Praxis Precision Medicines in April 2026.
This content is provided for educational purposes only and is not intended as medical advice, diagnosis, or treatment. Always consult a qualified healthcare professional before making decisions about your child's care. The information in this post reflects publicly available data as of June 2026 and may not reflect the most current developments.
This work depends on your support. Sign up for the SCN2A patient registry to ensure your family's voice shapes what comes next. And please consider making a donation to help fund the research and resources that bring us all closer to treatments.
1. Praxis Precision Medicines. "Praxis Precision Medicines Receives FDA Breakthrough Therapy Designation for Elsunersen." GlobeNewsWire, June 22, 2026.
2. Praxis Precision Medicines. "Positive Results from the EMBRAVE Part A Trial of Elsunersen." April 6, 2026.
3. U.S. Food and Drug Administration. "Breakthrough Therapy." FDA.gov.
4. Li, M., et al. "Antisense oligonucleotide therapy reduces seizures and extends life span in an SCN2A gain-of-function epilepsy model." JCI Insight, 2021.
5. Praxis Precision Medicines. "Alignment with FDA on Simplified and Accelerated Registrational Pathway for Elsunersen." December 9, 2025.
6. Quilon, R., et al. "Antisense oligonucleotides as a precision therapy for developmental and epileptic encephalopathies." CNS Neuroscience & Therapeutics, 2024.
7. Praxis Precision Medicines. "Q1 2026 Corporate Update." May 7, 2026.
Vlad Magdalin
