By Daniel Richardson
Editor-in-Chief, Archysport
Boston, MA – Biogen is making significant strides in the fight against spinal muscular atrophy (SMA) with promising early results from its Phase 1b clinical trial of salanersen, a novel antisense oligonucleotide (ASO) therapy. The data, presented at the 2026 MDA Clinical & Scientific Conference, suggests salanersen could offer a new treatment option for SMA patients who haven’t fully responded to existing therapies, including gene therapy and Biogen’s own Spinraza.
Spinal muscular atrophy is a rare genetic neuromuscular disease characterized by the loss of motor neurons, leading to muscle weakness and atrophy. Without treatment, severe cases can be fatal before the age of two. The development of treatments like Spinraza and gene therapies have dramatically altered the prognosis for many, but a subset of patients still experience limited clinical improvement. Salanersen aims to address this unmet need.
The Phase 1b trial focused on children with SMA who had previously received gene therapy but continued to exhibit insufficient clinical improvement. According to Biogen, half of the patients in the study achieved a new level of motor development, as defined by the World Health Organization (WHO) motor milestones. Importantly, researchers also observed a reduction in neurofilament light chain (NfL), a biomarker of nerve damage, indicating potential neuroprotective effects.
“This is encouraging data, particularly for those patients who haven’t seen the full benefit from existing treatments,” explained a Biogen spokesperson. “Salanersen is designed to operate through a similar mechanism to Spinraza, but with a modified backbone chemistry that allows for increased potency and a less frequent dosing schedule.”
Currently, Spinraza requires maintenance treatment every four months. Salanersen, however, is being developed as a once-yearly ASO, potentially offering a significant convenience factor for patients and families. This reduced dosing frequency is a key differentiator and could improve adherence to treatment.
The drug functions by promoting the production of SMN protein, which is deficient in individuals with SMA. Specifically, salanersen targets SMN2 pre-mRNA splicing, a process that influences the amount of functional SMN protein produced. The modified chemical structure of salanersen is intended to enhance its effectiveness.
Biogen acquired the rights to salanersen from Ionis Pharmaceuticals in 2021 for a $60 million upfront payment. This isn’t the first collaboration between the two companies; Biogen previously licensed Spinraza from Ionis, demonstrating a strong partnership in the SMA treatment space. The initial agreement for Spinraza involved a $290 million option exercise on top of a $30 million upfront payment.
Building on the positive Phase 1b results, Biogen has initiated a global Phase 3 clinical program, dubbed STELLAR, encompassing three separate trials. These trials will further evaluate the efficacy and safety of salanersen in a larger patient population. The launch of the Phase 3 program signals Biogen’s confidence in salanersen’s potential and its commitment to advancing SMA treatment options.
The success of salanersen could represent a significant advancement in SMA care. While gene therapy and Spinraza have revolutionized treatment, they aren’t universally effective, and ongoing treatment is often required. A once-yearly ASO therapy like salanersen could offer a valuable alternative, particularly for those who haven’t responded optimally to existing options. The reduction in NfL levels observed in the Phase 1b trial also suggests a potential for neuroprotection, which could translate to long-term benefits for patients.
The next steps will be closely watched as the STELLAR trials progress. The results of these trials will be crucial in determining whether salanersen can secure regulatory approval and ultimately grow a widely available treatment for SMA. For patients and families affected by this devastating disease, the promise of a more convenient and effective therapy offers a renewed sense of hope.
What’s Next: Biogen anticipates enrolling patients in the STELLAR trials throughout 2026, with initial data expected in late 2027 or early 2028. Investors and the SMA community will be keenly following the progress of these trials, as they represent a critical step towards potentially expanding treatment options for this challenging condition.
