First child dosed in study of new Dravet syndrome treatment

The first child has received ION337 in an open-label Phase 1/2 study, marking the start of clinical testing of this experimental therapy for Dravet syndrome.

The study, called ASCEND (NCT07531745), is recruiting up to 32 children, ages 2 to 12, who have been diagnosed with Dravet syndrome and have been on a stable dose of antiseizure medication for at least four weeks. The main goal is to test the safety and tolerability of ION337 when delivered intrathecally (into the spinal fluid) as a single dose and multiple doses.

“The first participant to receive ION337 in the ASCEND study marks an important step toward advancing a potential [disease-modifying] therapy for people living with Dravet syndrome,” Holly Kordasiewicz, PhD, executive vice president and chief development officer of Ionis Pharmaceuticals, which is developing the therapy, said in a company press release.

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Study will assess safety of therapy at different dose levels

Dravet syndrome is most often caused by mutations in one copy of the SCN1A gene, which disrupt the production of the NaV1.1 sodium channel, a protein essential for normal signaling between nerve cells in the brain. Without enough working NaV1.1 channels, nerve cells become overactive and fire too many electrical signals. This can trigger seizures and contribute to other symptoms, including developmental delays and behavioral problems.

ION337 is an investigational antisense oligonucleotide (ASO) therapy designed to increase production of the NaV1.1 sodium channel from the healthy copy of the SCN1A gene. By boosting levels of this protein, the therapy aims to address the underlying cause of Dravet and help reduce seizures. Its ASOs are modified with N-methylacetamide, a chemical change that helps the therapy remain active in the body longer, potentially allowing patients to receive less frequent dosing.

The ASCEND clinical study begins with a six-month single-ascending-dose phase, in which different dose levels are tested one at a time. This is followed by a two-year multiple-ascending-dose phase, during which patients receive repeated doses every six months. All patients will be monitored for an additional seven months to assess long-term safety.

The main goal is to test the therapy’s safety by monitoring side effects, serious side effects, changes in blood and laboratory tests, vital signs, heart activity, physical and neurological tests, and suicidal thoughts or behaviors over six months in the single ascending dose phase and a total of about 2.5 years in the multiple ascending dose phase.

The study will also measure how ION337 moves through and remains in the body by tracking its levels in the blood and cerebrospinal fluid, the liquid that surrounds the brain and spinal cord. In addition, researchers will assess the treatment’s effectiveness by measuring the percentage change from the start of the study in the frequency of major motor seizures over 28-day periods.

The U.S. Food and Drug Administration has granted ION337 fast-track designation, a program that helps speed the development and review of therapies for serious diseases with unmet medical needs. It includes more frequent communication with the FDA and access to rolling review, which means data can be submitted as they become available rather than waiting for the full package before filing for approval.