Biogen reports Phase 1b data showing salanersen reduced neurodegeneration markers and improved motor milestones in SMA patients previously treated with onasemnogene abeparvovec, while advancing a global Phase 3 program.
Written By: Nikita Jha, BPharm
Reviewed By: Pharmacally Editorial Team
Biogen Inc. reported additional Phase 1b data for its investigational antisense oligonucleotide salanersen (BIIB115) showing reductions in neurodegeneration markers and improvements in motor function in children with spinal muscular atrophy (SMA) previously treated with gene therapy. The results were presented at the 2026 Muscular Dystrophy Association (MDA) Clinical & Scientific Conference, alongside the design of the company’s global Phase 3 development program.
The Phase 1b study (NCT05575011) evaluated 24 children aged 0.5 to 12 years who had previously received onasemnogene abeparvovec-xioi gene therapy (Zolgensma) but continued to experience suboptimal clinical outcomes. Participants received at least two intrathecal doses of salanersen at 40 mg or 80 mg, with the 80 mg dose selected for further evaluation in Phase 3 trials.
Among participants with elevated baseline neurofilament light chain (NfL) levels, a biomarker of ongoing neurodegeneration, treatment with salanersen produced a 75% reduction in NfL concentrations at six months, with reductions maintained during follow-up.
All participants demonstrated improvement from baseline on at least one clinical endpoint. Notably, 12 of 24 children achieved at least one new World Health Organization motor milestone, while all participants maintained the motor milestones recorded at baseline.
Stephanie Fradette, PharmD, head of the Neuromuscular Development Unit at Biogen, said the encouraging Phase 1b results have enabled the rapid launch of the Phase 3 STELLAR-1, STELLAR-2, and SOLAR studies, which aim to clarify salanersen’s role in the future treatment landscape for SMA.
Salanersen was generally well tolerated across both dose groups. Most adverse events were mild to moderate, with upper respiratory tract infection and vomiting reported most frequently in the 40 mg group and pyrexia and upper respiratory tract infection in the 80 mg group.
In parallel with the clinical data, Biogen presented the design of its Phase 3 clinical development program, which will evaluate once-yearly salanersen 80 mg across a broad population of patients with SMA. The program includes three global studies: STELLAR-1, an open-label study in presymptomatic infants younger than six weeks with a genetic diagnosis of SMA; STELLAR-2, a randomized, double-blind, sham-controlled study, will evaluate salanersen initiated about six months after presymptomatic treatment with the gene therapy onasemnogene abeparvovec-xioi in infants with SMA who received the therapy at six weeks of age or younger.; and SOLAR, an open-label study in adolescents and adults aged 15 to 60 years who are treatment-naïve or previously treated with risdiplam.
According to the company, STELLAR-1 has already begun screening, while SOLAR is expected to initiate in the second quarter of 2026 and STELLAR-2 in the third quarter of 2026. The STELLAR studies are designed to compare early treatment strategies, including salanersen alone, gene therapy alone, and salanersen as an add-on to gene therapy, to inform future treatment approaches for SMA.
Thomas Crawford, M.D., of Johns Hopkins Medicine, said the new Phase 1 data strengthen confidence in salanersen’s emerging clinical profile and highlight its potential to further improve outcomes in Spinal Muscular Atrophy, where unmet needs remain despite major therapeutic advances.
Salanersen is an intrathecally administered antisense oligonucleotide designed to correct SMN2 pre-mRNA splicing, thereby increasing production of survival motor neuron (SMN) protein. Its novel backbone chemistry is intended to enable high potency and once-yearly dosing.
Biogen licensed global development, manufacturing, and commercialization rights for the therapy from Ionis Pharmaceuticals, which originally discovered the drug.
Spinal muscular atrophy is a rare genetic neuromuscular disease caused by deficiency of the SMN protein due to mutations or loss of the SMN1 gene, leading to progressive motor neuron degeneration, muscle weakness, and functional decline. The disease affects approximately 1 in 10,000 live births and remains a leading genetic cause of infant mortality.
Reference
Biogen Presents Additional Salanersen Data Showing New Motor Milestones Achieved in Children with SMA Previously Treated with Gene Therapy, 11 March 2026, Biogen Presents Additional Salanersen Data Showing New Motor Milestones Achieved in Children with SMA Previously Treated with Gene Therapy | Biogen
A Study to Learn About the Safety of BIIB115 Injections and How BIIB115 is Processed in the Bodies of Healthy Adult Male Volunteers and of Pediatric Participants with Spinal Muscular Atrophy Who Previously Took Onasemnogene Abeparvovec, ClinicalTrials.gov ID NCT05575011, https://clinicaltrials.gov/study/NCT05575011
About the Writer
Nikita Jha BPharm is a pharmacy graduate with expertise in clinical research, pharmacovigilance, and medical writing. In her words, she is passionate about translating complex scientific data into clear, accurate healthcare communications that advance drug safety and patient care.