SMA Drug Breakthrough
FDA Grants Breakthrough Therapy Designation to Biogen's Salanersen for Spinal Muscular Atrophy Treatment
The U.S. Food and Drug Administration granted Breakthrough Therapy Designation to Biogen's salanersen for spinal muscular atrophy on June 4, 2026, Montreal Gazette reported. The move fast-tracks development of a drug that could replace painful, frequent spinal injections with a single yearly dose — a major leap for SMA patients.
The designation follows Phase 1b trial data showing 50% of participants — 12 of 24 children — gained at least one new motor skill, such as sitting or walking, according to StreetInsider. Crucially, some of those children had already failed gene therapy, the current gold-standard treatment.
What Salanersen Does and Why It Matters
SMA is a rare genetic disease that destroys the nerves controlling muscle movement. Babies with severe forms often die before age two. Salanersen is an antisense oligonucleotide — a molecular switch that tells the body to produce more of the SMN protein it is missing. It works the same way as Biogen's older drug Spinraza, but with a new chemical backbone that makes it far more powerful, according to CGTlive.
That extra power means patients need just one spinal injection per year instead of three. By comparison, Roche's rival drug Evrysdi requires a daily oral dose. Dr. Thomas Crawford of Johns Hopkins Medicine described "growing scientific and clinical enthusiasm" for the drug's potential to deliver higher efficacy with less frequent dosing, as cited by GlobeNewswire.
Phase 1b Data Surprised Even Researchers
The Phase 1b results, presented at the Muscular Dystrophy Association conference in Orlando in March 2026, showed a 75% mean reduction in neurofilament light chain levels at six months, according to Investing.com. Neurofilament light chain is a biomarker for nerve damage — lower levels mean less nerve destruction.
The most striking finding involved children who had already received Novartis' Zolgensma gene therapy and still declined. After starting salanersen, some gained the ability to sit or walk. Dr. Diana Castro noted the FDA's designation "recognizes that there is continued unmet need" and called the gene therapy rescue results unexpected, per StreetInsider.
Biogen Bets Its SMA Future on This Drug
Spinraza, Biogen's first SMA drug approved in 2016, once generated $2.1 billion per year. By 2025, annual sales had fallen to $1.55 billion as Zolgensma and Evrysdi took market share, according to Fierce Pharma. CEO Chris Viehbacher has said Biogen is "pinning SMA recovery" on high-dose Spinraza and the transition to salanersen.
Analysts at Jefferies and BMO Capital Markets call the Breakthrough Designation a major de-risking event. They expect Phase 3 data by 2028, which could let Biogen reclaim leadership in the SMA market. Biogen's stock has already climbed 48.6% over the past year to $195.96, per Investing.com.
Patient Community Welcomes News but Stresses Access Gaps
Kenneth Hobby, president of Cure SMA, said the designation "affirms what our SMA community has recently communicated: urgent, unmet needs remain," according to The Observer. Many patients still experience nerve damage even after receiving treatments that cost up to $2.1 million — Zolgensma's list price — or $750,000 for the first year of Spinraza.
Biogen plans to test salanersen in three patient groups: presymptomatic newborns, infants who previously received gene therapy, and teenagers and adults. The FDA's Breakthrough Designation means more frequent agency guidance and a faster review clock — but final approval still hinges on Phase 3 results, Weekly Voice noted.
Sentiment
NeutralPublishers
5
Articles
5
Reach
5
