Biogen's Salanersen Shows Promise for SMA Patients Unresponsive to Zolgensma

Biogen has unveiled encouraging interim results from a phase 1 trial of salanersen, a potential new treatment for spinal muscular atrophy (SMA). The antisense oligonucleotide therapy demonstrated efficacy in children who had previously received Novartis' gene therapy Zolgensma but were still struggling with motor function.

Interim Trial Results

The phase 1 study, which included 24 children aged five months to 12 years, showed that salanersen reduced levels of neurofilament light chain (NfL), a biomarker of neurodegeneration, by an average of 70% at six months. This reduction was sustained for a full year.

In a subgroup of eight patients aged 2-12 who received a 40 mg dose and had at least one year of follow-up, half achieved new motor function milestones. These improvements included walking, crawling, standing, or sitting independently.

Dr. Valeria Sansone, Professor of Neurology at the University of Milan and a principal investigator for the trial, highlighted a particularly striking case: "To see a child dosed with gene therapy at one year of age and still unable to sit without support at age five then gain the ability to sit independently just three months after initiating salanersen—that is unexpected."

Safety Profile and Mechanism of Action

Salanersen demonstrated a "generally well-tolerated safety profile" at both 40 mg and 80 mg doses. The most common side effects were fever (40% of patients) and upper respiratory tract infection (29%). No serious adverse events were linked to the treatment itself.

Like Biogen's approved SMA therapy Spinraza, salanersen is an antisense oligonucleotide. However, the company aims for greater potency and a more convenient once-yearly dosing schedule with this new drug.

Future Developments

Based on these promising results, Biogen is now engaging with global regulators about the design of a phase 3 trial for salanersen. Stephanie Fradette, Biogen's head of neuromuscular development, emphasized the ongoing need for new treatments: "Despite the remarkable therapeutic advancements in the field of SMA over the past decade, there remains critical unmet needs."

As the only biopharma company with both an approved SMA therapy and a potential follow-up in clinical trials, Biogen is positioning itself as a leader in this therapeutic area. However, the company acknowledges that larger trials are needed to "further understand the effects that salanersen can have in both previously treated and treatment-naïve individuals."