The antisense oligonucleotide drug nusinersen is the first therapy approved by the U.S. Food and Drug Administration to treat children and adults with spinal muscular atrophy.
The drug was developed by Ionis Pharmaceuticals and will be marketed by Biogen under the brand name Spinraza. The antisense oligonucleotide drug is administered via an intrathecal injection and promotes transcription of the full-length survival motor neuron (SMN) protein from the SMN2 gene.
The efficacy of nusinersen was tested during a randomized clinical trial in 121 patients with infantile-onset spinal muscular atrophy who were diagnosed before the age of 6 months or were younger than 7 months at the time of their first dose. Patients were randomized 2:1 to receive an injection of nusinersen into the fluid surrounding the spinal cord or undergo a mock procedure without drug injection (a skin prick).
A total of 82 of 121 patients who were randomized were eligible for an interim analysis of the results that was requested by the FDA. The results showed 40% of patients treated with nusinersen achieved improvement in motor milestones as defined in the study, whereas none of the control patients did. The side effects during the clinical trials among patients on nusinersen included upper respiratory infection, lower respiratory infection, and constipation. Warnings and precautions include low blood platelet count and renal toxicity. Neurotoxicity was observed in animal studies.
Read the full announcement from the agency here.