Biogen Gets FDA Breakthrough Designation for Spinraza Successor Salanersen

By Colin Kellaher

Biogen has won U.S. Food and Drug Administration breakthrough-therapy designation for its proposed salanersen treatment for the neuromuscular disease spinal muscular atrophy, or SMA.

The Cambridge, Mass., biotechnology company on Thursday said the designation is supported by a Phase 1b study that showed unexpected improvements on exploratory endpoints in children previously dosed with gene therapy who gained critical functions, such as sitting and walking, after receiving salanersen.

The FDA's breakthrough-therapy designation aims to expedite the development and review of a drug for serious conditions when preliminary clinical evidence shows the drug might offer substantial improvement over available therapies.

Spinal muscular atrophy is a rare genetic disease characterized by a loss of motor neurons in the spinal cord and lower brain stem, resulting in severe, progressive muscle atrophy and weakness.

Salanersen, which is designed for once-yearly dosing, is a potential successor to Biogen's blockbuster SMA drug Spinraza, which generated worldwide sales of nearly $1.55 billion last year and requires dosing three times a year.

As with Spinraza, Biogen licensed the global rights to develop, manufacture and commercialize salanersen from Ionis Pharmaceuticals, which discovered the drug.

Biogen is working to advance a trio of Phase 3 studies of salanersen.

Write to Colin Kellaher at colin.kellaher@wsj.com

(END) Dow Jones Newswires

June 04, 2026 08:09 ET (12:09 GMT)