Study summary

Starting tofersen early slowed decline more than starting later

Tofersen long-term follow-up · 108 people, phase 3 plus extension · Published February 2026, JAMA Neurology; FDA approved 2023

What was tested

Tofersen, an antisense drug injected into the spinal fluid that lowers the toxic SOD1 protein, in people with ALS caused by SOD1 gene variants, followed through an open-label extension.

What they found

• People who started tofersen early declined less in function, strength and breathing than those who started 6 months later.
• Neurofilament, a blood marker of nerve damage, fell substantially.
• Applies only to the roughly 2% of ALS caused by SOD1 variants.

What it means

Proof that a gene-targeted drug can slow a form of ALS, and that earlier treatment matters.