Biogen Advances Presymptomatic SMA Strategy With New Salanersen Trial

Biogen Inc. (BIIB) announced an update on their ongoing clinical study.

Study Overview
This Phase 3 Biogen study, officially titled “An Open-Label Study to Assess the Efficacy and Safety of Multiple Doses of Salanersen (BIIB115) Delivered Intrathecally to Treatment-Naïve, Presymptomatic Infants With Genetically Diagnosed Spinal Muscular Atrophy,” aims to see if treating babies with spinal muscular atrophy (SMA) before symptoms appear can prevent or reduce disease impact. The trial focuses on whether early use of salanersen improves key movement milestones, such as sitting and walking, in infants identified by genetic testing, a potentially important step in reshaping the SMA treatment landscape.

Intervention/Treatment
The study tests salanersen (BIIB115), a drug delivered directly into the fluid around the brain and spinal cord. It is designed to boost production of an essential protein that SMA patients lack, helping nerves and muscles work better. All enrolled infants receive salanersen, with repeated doses over several years, to see if early, ongoing treatment can keep them symptom-free or limit the severity of SMA.

Study Design
This is an interventional, single‑arm study, meaning every participant receives the same treatment and there is no placebo or comparison group. It is open label, so doctors and families know the child is getting salanersen. The main purpose is treatment: to track how well the drug works and how safe it is in very young children who have SMA on genetic testing but no symptoms yet.

Study Timeline
The study is listed as “not yet recruiting,” with start preparations tied to an initial submission date of 24 October 2025, signaling that Biogen is still setting up trial sites and processes. Primary completion will occur once enough data are collected on early movement milestones such as sitting and walking, which will be key for regulatory and clinical decisions. Full completion, expected several years after first dosing, will cover longer‑term safety and durability of benefit. The latest update on 9 January 2026 shows the protocol is active and being refined, an important marker that the program remains a current strategic priority for Biogen.

Market Implications
For investors, this presymptomatic SMA trial extends Biogen’s neuromuscular franchise beyond its existing therapy Spinraza and pushes the company further into early‑intervention medicine. Success here could strengthen Biogen’s competitive position against rival SMA treatments, including Novartis’s gene therapy and Roche’s oral option, by targeting babies before any visible damage occurs. If early data eventually show strong motor outcomes and acceptable safety, the read‑through could support premium pricing, longer treatment duration, and deeper penetration in screened newborn populations, all supportive of long‑term revenue visibility. Conversely, delays in recruitment, weaker‑than‑expected results, or safety concerns could dampen sentiment, particularly as investors remain focused on Biogen’s ability to diversify and stabilize earnings beyond legacy products and Alzheimer’s volatility. With the study not yet recruiting and no efficacy data available, near‑term stock impact should be modest, but continued progress will be watched closely as a medium‑term growth option in a high‑value rare disease category.

The study is currently in the setup and update phase, with ongoing information and future results to be made available through the ClinicalTrials portal.

To learn more about BIIB’s potential, visit the Biogen Inc. drug pipeline page.