Salanersen / B11B115 (Biogen)
Salanersen / B11B115 (Biogen)
Page last updated: 17th September 2026
Topline results from Biogen on Phase 1B trial and commencement of Phase 3 trials
Salanersen is an antisense oligonucleotide similar to nusinersen that targets the underlying cause of SMA. It has been designed to be more effective than nusinersen and has the potential to enable treatment of SMA with just a single injection per year (by lumbar puncture), rather than every few months.
Biogen have now released the latest information from the Phase 1B trial of Salanersen, which is being delivered to people who had previously been treated with Zolgensma, but had a suboptimal response to the gene therapy.
For the trial, 24 participants were divided into two groups. Each group received either a 40 mg or 80 mg dose of Salanersen directly into the fluid bathing the brain and spinal cord (i.e., “intrathecally”). The latest results come from participants who have received at least two doses of Salanersen.
These interim results show that Salanersen is safe and well-tolerated in people with SMA. Reductions in the levels of neurofilament protein in blood, which is a key marker of nerve cell death, were observed upon treatment. Furthermore, half of the participants that had completed the 1-year follow up achieved new motor milestones.
Due to the favourable outcomes from the Phase 1B trial, Phase 3 clinical trials for Salanersen are now active and recruiting at sites in the United States, Australia, Brazil, China and Japan. There are no sites currently recruiting in the UK.
STELLAR-1 is an open-label study to evaluate the effects of Salanersen in young (under 6 weeks old), treatment-naïve and clinically pre-symptomatic infants with a genetic diagnosis of SMA.
STELLAR-2 is a randomised, double-blind, sham-controlled study that will evaluate the effects of Salanersen when initiated approximately 6 months after Zolgensma in infants with SMA who received pre-symptomatic treatment at or before 6 weeks of age.
SOLAR is an open-label study designed to assess the effects of Salanersen in teens and older adults (aged 15-60 years) with SMA who were previously treated with Risdiplam or have not yet received treatment.
Further Information
Clinicaltrials.gov: Phase 1 Trial
14th July 2025
Biogen announce positive interim results of salanersen phase 1 trial.
Biogen recently announced interim data from a phase 1 trial of salanersen (also known as BIIB115). This is anantisense oligonucleotide similar to nusinersen that targets the underlying cause of SMA.
Salanersen has been designed to be more effective than nusinersen. It has the potential to enable treatment of SMA with just a single injection per year year. The trial tested this approach in people who had previously been treated with zolgensma, but had a suboptimal response to the gene therapy.
For the trial, 24 participants were divided into two groups. Each group received either a 40 mg or 80 mg dose of salanersen directly into the fluid bathing the brain and spinal cord (i.e., “intra-thecally”). This was Part B of the trial. Part A first tested the drug in healthy adult male volunteers and was shown to be safe and well-tolerated.
The interim results from Part B of the trial show that both doses of salanersen are safe and well-tolerated in people with SMA. This was the main purpose of the trial. Nevertheless, in addition, the levels of neurofilament protein in blood, which is a key marker of nerve cell death, were shown to become reduced upon treatment.
This alone does not necessarily indicate that the treatment is working, but it is a positive sign. Especially when combined with early evidence of salanersen causing clinically meaningful improvements in motor function. Half of the tested participants achieved milestones, such as crawling and walking, that they could not perform before the trial.
These data are positive enough for Biogen to engage with global health authorities regarding the design of phase 3 studies of salanersen. These trials will be designed to determine in a larger patient cohort whether salanersen is an effective treatment for SMA.
Further Information
Biogen’s Community Statement to SMA Europe >
18 March 2022
In response to our request, Biogen shared this community update to announce that they are moving ahead with an early-stage investigation into a new treatment for SMA that could potentially treat further unmet needs:
The compound, BIIB115, acquired from Ionis Pharmaceuticals, is currently in the pre-clinical stage of development and builds on knowledge of nusinersen¹′², which was designated an “orphan medicine” for rare disease in April 2012³.
Nusinersen and BIIB115 are both “antisense oligonucleotides” (ASOs), small snippets of synthetic genetic material, or “molecular patches”, that target the underlying pathology of SMA¹′².
It is too early to draw comparisons given the early stages of investigation. However, clinical trials are being planned to help understand the ASO’s dosing as well as its safety, tolerability and efficacy profiles. The clinical trial process is a rigorous one with multiple important phases. Initial clinical trials of experimental treatments focus on understanding their safety profile. Establishing the efficacy of BIIB115 will come in later stage studies.
Initial plans for BIIB115 clinical trials are in development. Biogen will be seeking feedback on their designs from our community. This communication is the first in a series to ensure that Biogen develops a clinical programme for BIIB115 that has been informed by the community.
References
- SPINRAZA (nusinersen). Summary of Product Characteristics February 2022.
- Biogen Press Release January 2022. Biogen Exercises Option with Ionis to Develop and Commercialize Investigational ASO for SMA.
- EMA nusinersen EPAR Summary for the public January 2018.