Ionis Pharmaceuticals To Expedite Development Of Rare Neurological Disease Candidate With FDA Breakthrough Status

Author: Vandana Singh | September 09, 2025 01:51pm

On Tuesday, the U.S. Food and Drug Administration (FDA) granted Breakthrough Therapy designation to Ionis Pharmaceuticals Inc.’s (NASDAQ:IONS) ION582 for Angelman syndrome (AS), a rare neurological disorder.

This designation follows promising results from the Phase 1/2 HALOS study, which showed significant clinical improvements in communication, cognition, and motor function, along with favorable safety data.

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The Breakthrough Therapy designation aims to speed up the review of treatments for serious conditions. ION582 has also shown potential for substantial improvement over existing therapies. Ionis launched the global Phase 3 REVEAL study earlier this year, expected to enroll children and adults with AS by 2026.

William Blair noted that the BTD marks a win for Ionis's neurology division, with analyst Myles Minter highlighting that the HALOS data impressed regulators, particularly given the challenges in assessing communication in AS patients.

In the competitive landscape, ION582 now tracks closely with Ultragenyx Pharmaceutical's (NASDAQ:RARE) apazunersen (GTX-102), which remains ahead after completing recruitment for the Aspire study.

Price Action: IONS stock is up 4.68% at $63.86 at the last check on Tuesday.

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Posted In: IONS RARE