This Tuesday, September 22, 2026, Otsuka and Ionis Pharmaceuticals have announced positive topline results from the Phase 3 FUSION trial, evaluating the investigational therapy called ulefnersen for people with FUS-ALS. According to the companies, the trial met its primary endpoint and showed statistically significant evidence that ulefnersen may slow disease progression compared to placebo. Researchers assessed several outcomes over approximately 17 months, including survival, the need for permanent ventilation support, disease progression requiring additional intervention, and changes in daily function measured using the ALSFRS-R scale.
The trial also reported a statistically significant decrease in neurofilament light chain (NfL), a biomarker of nerve cell damage that is increasingly used in ALS clinical trials to assess whether a therapy may be reducing the underlying disease process. At a group level, higher NfL levels are generally associated with faster disease progression, and substantial reductions, often around 30% or greater, are typically considered meaningful. The companies have not yet reported how much NfL levels decreased during the trial. However, seeing a meaningful decrease in NfL alongside clinical benefits adds to growing evidence that changes in this biomarker can be indicative of whether a treatment is making a meaningful difference for people living with ALS.
It was also reported that ulefnersen demonstrated a favourable safety and tolerability profile, with most adverse events described as mild or moderate.
The results announced so far are high-level findings released by the companies, and as with any clinical trial announcement, we look forward to reviewing the full data as it becomes available. Additional analyses are ongoing, and detailed data will be presented at a future scientific conference and submitted for publication in a scientific journal. Researchers will also continue monitoring participants through the study’s open-label extension, where all participants receive ulefnersen.
Otsuka and Ionis have stated that they plan to discuss the results with regulatory agencies, including the U.S. Food and Drug Administration (FDA), to explore potential pathways toward approval. Information about regulatory review and access pathways in Canada is not yet available, and we will continue to share more as we hear from the companies and advocate for timely access.
While the full data are still being analyzed, these findings add to the most significant advances to date for the ALS community. Following the approval of Qalsody (tofersen) for SOD1-ALS, the results add to growing evidence that precisely targeting the biological drivers of ALS can lead to meaningful clinical benefit and may fundamentally change how certain forms of the disease are treated.