Fourteen months of treatment with Spinraza (nusinersen) resulted in improved motor function in a previously untreated 15-year-old boy with late-onset spinal muscular atrophy (SMA), a case report in South Korea shows.
The case study, “Effect of Nusinersen in a late onset spinal muscular atrophy patient for 14 months,” was published in the journal Medicine.
Spinraza, developed by Biogen, became the first disease-modifying treatment to be approved in the U.S. for all types of SMA in December 2016. Similar decisions soon followed in the European Union, Brazil, Japan, Australia, and other countries.
The therapy was approved in January 2018 in South Korea, but a reimbursement agreement between Biogen and the National Health Insurance Service was only reached in April 2019.
Spinraza works by increasing the production of the survival motor neuron protein (SMN) — essential for motor neuron and muscle health — that is largely absent or insufficient in SMA patients due to mutations in the SMN1 gene.
The therapy is administered directly into the spinal canal at a recommended treatment schedule of four doses in the first two months, followed by maintenance treatment every four months.
Since its approval was based on clinical trials of infants and young children with SMA, data on Spinraza’s effectiveness in adolescents and adults rely mainly on case reports and real-world studies.
Now, researchers in South Korea have reported the safety and effectiveness of 14 months of Spinraza treatment in a 15-year-old boy with late-onset, milder SMA (type 2 or 3 disease).
The boy was referred to their neurology clinic at age 13 due to progressive muscle weakness. He had a history of delayed achievement of motor milestones at 18 months of age and an SMA diagnosis was confirmed with genetic testing when he was 3.
Neurological evaluation at the clinic confirmed the presence of muscle weakness in his legs and shoulders, and showed evidence of nerve cell loss and associated compensatory changes. SMA-related changes in muscle tissue architecture were also observed in his legs, while lung function tests were within the normal range.
Additional genetic testing revealed the presence of three copies of the SMN2 gene, suggestive of late-onset SMA. SMN2 is a backup gene that can partially compensate for the loss of SMN1-derived SMN and whose higher number of copies is associated with later disease onset and milder severity.
The boy began Spinraza treatment at 15 when the therapy’s reimbursement was approved in the country.
Over the 14 months of treatment, he showed gradual improvements in motor function, which were considered clinically meaningful by the end of the treatment period.
Motor function changes were assessed with the six-minute walk test — showing an improvement from 87.5 to 113 walked meters in six minutes — and the Hammersmith functional motor scale extended (HFMSE), which detected a three-point gain.
Particularly, among HFMSE tasks, the boy became able to prop on extended arms (reflecting upper body function) and to get to his hands and knees with his head up and hold the position for a count of three, both without help. His lung function also showed signs of improvement.
Regarding safety, the boy had a mild headache after the first spinal canal injection, which was easily resolved with medication. No serious adverse events or those preventing him from receiving the therapy were reported.
“More studies on late onset SMA [are] needed to accurately understand the efficacy of [Spinraza] and our case adds to the favorable outcome in the categories of late onset SMA patients,” the researchers wrote.
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