Otsuka and Ionis Pharmaceuticals said their investigational RNA-targeted medicine ulefnersen met the primary endpoint in the Phase 3 FUSION trial for FUS-ALS, a rare inherited form of amyotrophic lateral sclerosis caused by mutations in the fused in sarcoma, or FUS, gene. The primary analysis showed statistically significant improvement versus placebo in a prespecified joint assessment of function and survival, including death, permanent ventilation, rescue treatment and changes in the ALS Functional Rating Scale Revised. The analysis included 73 participants and produced a p-value of 0.0005. Ulefnersen also improved key secondary measures, including serum neurofilament light chain and time to death, ventilation, rescue or disease-related withdrawal. Most adverse events were mild or moderate, and the companies reported favorable safety and tolerability. Ionis shares rose 2.58% to $46.06 following the announcement. Otsuka plans discussions with the U.S. Food and Drug Administration and other health authorities about potential expedited submission pathways, while the companies will present detailed results and seek publication in a peer-reviewed medical journal. Ionis remains eligible for regulatory and commercial milestone payments and tiered royalties under its 2024 licensing agreement with Otsuka.