Ionis Pharmaceuticals has dosed the first participant in its Phase I-II ASCEND trial evaluating ION337, an investigational ribonucleic acid (RNA)-targeted therapy, for children with Dravet syndrome.
Dravet syndrome is a rare and severe neurological disorder characterised by early onset, prolonged seizures, developmental delays and a risk of sudden death.
The open-label trial enrolled patients aged between two and 12 years who have a clinical diagnosis of Dravet syndrome.
It includes a six-month single-ascending dose segment followed by a 24-month multiple-ascending dose phase, in which ION337 is given every six months, and is concluded with a seven-month safety follow-up.
Developed using Ionis’ N-Methylacetamide (NMA) technology, ION337 aims to improve the potency of splice-modulating antisense oligonucleotides, with the goal of supporting sustained activity with less frequent, intrathecal dosing.
The US Food and Drug Administration (FDA) has granted fast track designation to ION337 for Dravet syndrome.
Ionis Pharmaceuticals executive vice-president and chief development officer Holly Kordasiewicz said: "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.
"ION337 is our first wholly owned medicine developed using Ionis’ advanced NMA technology, which is designed to enhance the potency of our medicines and potentially support infrequent intrathecal dosing of every six months or less.
"This milestone reflects a new wave of scientific innovation across Ionis’ advancing neurology pipeline for people living with serious neurological conditions. We look forward to advancing the development of ION337 alongside the Dravet syndrome community.”
ION337 is designed to increase the production of the NaV1.1 protein, which is often reduced in patients with Dravet syndrome due to SCN1A gene variants.
In September 2025, Ionis Pharmaceuticals reported encouraging topline outcomes from the randomised Phase III CORE and CORE2 trials of the investigational RNA-targeted therapy, olezarsen, in those with severe hypertriglyceridemia.
