Spinal Muscular Atrophy (SMA) is a rare neuromuscular genetic disorder. Infants born with this disease have muscular weakness and wasting which worsens with age. The incidence of the disease is approximately 1 in 10,000 live births. Spinal Muscular Atrophy Type 1 is the most common and most severe type. Most children born with this type do not survive past early childhood due to respiratory failure.
In May 2019, the US Food and Drug Administration approved the gene therapy Zolgensma (onasemnogene abeparvovec-xioi) to treat SMA in children under two years of age. Zolgensma is a one-time, IV-administered therapy. This therapy has shown an improvement in muscle movement and survival.
A new phase 1b study by Biogen is now evaluating the drug salanersen in patients with SMA who have already received the gene therapy Zolgensma. In this study, salanersen was evaluated in children who continued to experience suboptimal clinical status despite having previously received Zolgensma. Patients in the study experienced a 75% reduction in neurofilament light chain levels, a biomarker used to assess neurodegeneration. Additionally, half of the patients achieved a motor function milestone based on World Health Organization standards.
Like Spinraza, salanersen corrects the splicing of a gene to increase production of survival motor neuron proteins, levels of which are low in people who have SMA. Salanersen, however, is more potent. Both drugs are administered intrathecally, but salanersen is administered once a year, as opposed to Spinraza, which requires maintenance dosing every four months.
Researchers also noted plans for a late‑stage study consisting of three separate trials of salanersen. The groups in the study include newborns, Zolgensma‑treated infants, and teens and adults who are either untreated or previously treated with the Spinal Muscular Atrophy drug Evrysdi.
Article written by Stacy Schumacher, RN, BSN, CMCN, Managed Care Specialist. The following sources were used as reference material for this article:
https://medlineplus.gov/genetics/condition/spinal-muscular-atrophy/