Study summary

A gene-targeted drug for FUS-ALS met its main goal in phase 3

FUSION trial · 89 people, phase 3 · Topline results September 22, 2026

What was tested

Ulefnersen, an antisense drug that lowers FUS protein, against placebo, in people with ALS caused by FUS gene variants, a rare and often early-onset form.

What they found

• The trial met its primary endpoint, combining daily function, survival without permanent ventilation and time to rescue treatment.
• Effect size and full safety data have not yet been released.
• An early access program opened alongside the results.

What it means

The second genetic form of ALS with a drug that works; full data and a filing are next.