Otsuka, OPDC and Ionis announced positive top‑line results from the Phase III FUSION trial of ulefnersen in patients with FUS‑ALS. The randomized, placebo‑controlled study met its primary endpoint on a joint‑rank composite of survival and functional outcomes through Day 505. Secondary endpoints and biomarkers, including serum neurofilament light chain, also favored ulefnersen, and most adverse events were mild or moderate. The companies will pursue regulatory discussions and plan further analyses and publications.
Ulefnersen Meets Primary Endpoint in Phase III FUSION Trial for FUS‑ALS — Otsuka & Ionis Report Positive Top‑Line Results
FUS-ALS is a rare
Otsuka Pharmaceutical Development & Commercialization (OPDC), Otsuka Pharmaceutical and Ionis Pharmaceuticals have announced encouraging top-line results from the Phase III FUSION trial evaluating ulefnersen for people with FUS‑ALS, a genetic form of amyotrophic lateral sclerosis caused by mutations in the FUS gene.
Trial Design and Primary Outcome
FUSION was a randomized, global, multi-center, placebo-controlled, double‑blind study conducted in participants diagnosed with FUS‑ALS. The trial met its primary endpoint: ulefnersen demonstrated a statistically significant benefit versus placebo on a composite measure combining functional impairment and survival through Day 505. The primary analysis used a joint‑rank method that incorporated time to death or permanent mechanical ventilation, time to rescue interventions, and changes from baseline in the ALS Functional Rating Scale–Revised (ALSFRS‑R).
Secondary Endpoints and Biomarkers
Secondary endpoints supported the primary finding. Reported results included statistically significant improvements in biomarkers — notably serum neurofilament light chain — and in composite clinical measures such as time to death or permanent ventilation, need for rescue interventions, and withdrawals due to disease progression.
Safety
Ulefnersen's safety profile in the study was consistent with a favorable tolerability profile: most adverse events were reported as mild or moderate in severity.
"Today's Phase III FUSION topline results mark a major milestone for people living with FUS‑ALS, reshaping what is possible for a community that has long faced this devastating disease with limited treatment options," said John Kraus, Executive Vice‑President and Chief Medical Officer at Otsuka. "As the first FUS‑ALS clinical trial to meet its primary endpoint, FUSION provides compelling evidence that a targeted genetic approach may help alter the course of disease."
Next Steps
Otsuka and Ionis plan to engage with the U.S. Food and Drug Administration (FDA) and other health authorities to explore expedited regulatory pathways. The companies will perform additional analyses of the FUSION data and expect to share more detailed results — including findings from an ongoing open‑label extension — at upcoming scientific meetings and through peer‑reviewed publication.
Background
FUS‑ALS is a rare and often rapidly progressing subtype of ALS with no approved therapies that directly target its genetic cause. These top‑line results represent an important advance for a patient population with high unmet medical need.
Original reporting: Clinical Trials Arena (a GlobalData brand).
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