Otsuka and Ionis report ALS drug ulefnersen meets primary endpoint in phase 3 trial

Otsuka and Ionis have completed the Fusion phase 3 trial of ulefnersen, an RNA‑targeted therapy for ALS patients with mutations in the FUS gene. The study enrolled 89 participants, with 73 forming the primary analysis set.

Ulefnersen was designed to lower production of the disease‑driving FUS protein. In the trial it demonstrated a statistically significant slowdown of disease progression compared with placebo on the primary endpoint, which assessed functional impairment and survival at week 72.

The partners also reported favorable outcomes on secondary measures such as the ALS functional rating scale and ventilation‑free survival, positioning them to seek expedited regulatory review with the FDA.