Spinraza shown to slow lung function decline in SMA patients with symptoms
Spinraza (nusinersen) is able to help slow lung function decline in people with spinal muscular atrophy (SMA), even if treatment is started when patients are already experiencing disease symptoms, a new study shows.
The beneficial effects of the approved SMA therapy on lung function were generally more pronounced among children with the condition than adults, according to the researchers.
Still, the data analysis found that patients who require a ventilator prior to starting Spinraza should expect to continue needing ventilation assistance after beginning treatment. Also, some individuals who don’t need such breathing assistance before treatment may still need to start using a ventilator after receiving Spinraza.
Overall, the study “showed that lung function decline may attenuate in symptomatic children with SMA during treatment with [Spinraza]. In addition, we showed that expiratory muscle strength increased during treatment in this group,” the researchers wrote. Better expiratory muscle strength can improve voice volume, swallowing ability, and breathing.
The study, “Lung Function and Respiratory Muscle Strength in Symptomatic Children and Adults With Spinal Muscular Atrophy Treated With Nusinersen,” was published in the journal Neurology.
SMA is a genetic disorder marked by muscle weakness. Both adults and children with the condition commonly experience difficulty breathing, typically due to weakness of chest muscles, as well as other factors such as scoliosis. That abnormal curvature of the spine can put physical pressure on the chest, making it harder to breathe.
Little data on Spinraza effects on lung function in SMA
Biogen‘s Spinraza was the first SMA treatment to win widespread approvals worldwide. It is administered by injection into the spinal canal, and works to boost levels of the SMN protein, a shortage of which causes the disease.
Clinical trials have demonstrated that Spinraza treatment can slow the decline of motor function for people with SMA, but there is comparatively little data on its effects on lung function.
To learn more, a team of scientists in the Netherlands analyzed data from more than 100 people with SMA types 1-3 who started on Spinraza between May 2017 and July 2025. All were already experiencing SMA symptoms when they began receiving the therapy.
“A better understanding of respiratory function trajectories in patients treated with [Spinraza] is crucial for improving patient counseling and care and for developing standardized longitudinal follow-up protocols. To address this, we conducted a longitudinal national cohort study,” the scientists wrote. “Our primary research question was how lung function and respiratory muscle strength change in symptomatic patients with SMA who started treatment with [Spinraza].”
The study involved 78 children and 42 adults. Several different lung function tests were measured, including forced vital capacity (FVC) and forced expiratory volume in 1 second (FEV1). Peak expiratory flow, or PEF, was also used. FVC measures the amount of air a person can blow out in a forceful breath, while FEV1 measures the amount of air blown out in just one second. PEF, meanwhile, looks at how fast someone can blow out air.
Slower decline seen for SMA patients after starting treatment
Prior to starting Spinraza, lung function measures generally showed worsening trends over time, which is consistent with the natural course of SMA, in which muscle weakness worsens as time goes on. After starting Spinraza, lung function still generally declined over time — but the decline was mostly slower than it had been prior to treatment.
In children, for whom the follow-up period ranged from 10.9 years before treatment initiation to 6.8 years after starting Spinraza, the changes for FVC, FEV1, and PEF were all statistically significant, meaning it’s extremely unlikely the differences seen were due to random chance. A benefit, representing a decline before treatment that changed to improvement upon taking Spinraza, in the annual rate of change in maximal expiratory pressure — the maximum pressure generated by the respiratory muscles during forced expiration — was found in children with SMA type 2.
In adults, whose follow-up period ranged from 24.7 years before to 4.7 years after the start of treatment, the results showed no differences in the trajectories of FVC, PEF, and PCF with Spinraza. But adults with SMA type 2 did show a significant change in FEV1, which went from a 1.4% decline prior to Spinraza to a 0.2% improvement after starting the disease-modifying therapy.
The researchers noted that patients who were older when they started Spinraza generally had worse lung function at the start of treatment. However, age at initiation showed no clear association with the therapy’s effect on lung function decline.
In addition to lung function tests, the researchers also conducted tests of respiratory muscle strength, essentially looking at how much force the chest muscles can apply when breathing in or out. These tests generally indicated improvements in respiratory muscle strength in children with SMA after starting Spinraza.
Initiating treatment did not allow us to wean any of our ventilated patients off home mechanical ventilation during follow-up. … Ongoing deterioration of lung function despite treatment with [Spinraza] was further reflected by the additional [six] patients who required ventilatory support during treatment.
Before starting Spinraza, 30 of the patients in this study required a ventilator to help them breathe. None of these patients was able to stop using a ventilator after starting Spinraza. Additionally, six patients who didn’t need a ventilator before Spinraza started on ventilation after initiating treatment.
“Initiating treatment did not allow us to wean any of our ventilated patients off home mechanical ventilation during follow-up,” the researchers wrote, adding that this is “most likely due to irreversible structural and mechanical changes in the lungs and thorax” in patients who have advanced disease.
“Ongoing deterioration of lung function despite treatment with [Spinraza] was further reflected by the additional [six] patients who required ventilatory support during treatment,” the scientists wrote.
These data, the team suggest, may help inform expectations for SMA patients who are considering starting treatment.
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