Spinraza treatment found to benefit adults with SMA types 2, 3 in study
Approved therapy seen to improve movement of diaphragm in chest
Treatment with Spinraza (nusinersen) can improve the movement ability of the diaphragm — the large muscle in the chest that helps pull air in and out of the lungs during breathing — in previously-untreated adults with spinal muscular atrophy (SMA), a study showed.
The study, which was investigating diaphragm ultrasound imaging in adults with the genetic disorder, also found that Spinraza aided in diaphragm mobility in individuals with SMA types 2 and 3.
This finding offers insight on a potential benefit of Spinraza treatment for adults with SMA, in addition to the study’s results that demonstrate the useful of ultrasound imaging for assessing patients.
Titled “Impaired diaphragmatic motility in treatment-naive adult patients with spinal muscular atrophy improved during nusinersen treatment,” the study was published in Muscle & Nerve. The work was funded by Biogen, which markets Spinraza.
Ultrasound imaging used to assess Spinraza treatment in adults
Breathing issues are a common problem for patients with SMA, and are one of the leading causes of death in people with the disorder. Breathing issues in SMA are caused in large part by weakness of the diaphragm.
Spinraza was the first therapy to be approved to treat SMA. Administered via injections through the spine, it has been proven to slow disease progression in clinical trials.
But these trials mainly included young children with severe disease, so it’s still not fully understood how Spinraza may benefit SMA patients who start on treatment as adults.
Here, researchers used ultrasound imaging to examine the diaphragm in 24 adults with SMA who started on Spinraza. Among them were 10 with SMA type 2, and 14 with type 3 disease.
On initial evaluation, the researchers noted that many of the patients had abnormally thick diaphragms, compared with reference ranges for healthy people. However, diaphragm thickness did not show a clear association with breathing function tests. The scientists speculated that the diaphragm may be doing extra work in these patients to compensate for reduced function of other chest muscles — ultimately giving this muscle more exercise so it becomes enlarged.
“We found increased diaphragm thickness in a remarkable proportion of patients in our cohort, and we hypothesize that the diaphragm compensates for the impairment of intercostal [chest] muscles during inspiration [breathing in] and therefore changes structurally,” the researchers wrote.
Prior to starting on Spinraza, nearly a third of the patients had abnormally low diaphragm movement, referred to as diaphragm excursion.
After more than two years (26 months) of treatment with Spinraza, the movement of the diaphragm increased significantly in these patients. Following 36 months, or more than three years on therapy, 23 of the 24 patients had diaphragm movement within the normal range for people who do not have SMA.
All but one patient regained normal diaphragmatic motility during [Spinraza] treatment and the spirometric [breathing function] parameters remained stable.
Moreover, measures of lung function were stable over the course of follow-up, which notably contrasts the typical course of untreated SMA , in which lung function tends to gradually worsen over time.
“All but one patient regained normal diaphragmatic motility during [Spinraza] treatment and the spirometric [breathing function] parameters remained stable,” the researchers concluded.
The scientists noted that this study is limited by its small size, but said the findings are “consistent with those of others, who reported stable or improved respiratory function in adult patients with SMA types 2 and 3 treated with” Spinraza.
The team added that this study supports the utility of ultrasound-based assessment of the diaphragm to monitor the response to treatment for SMA patients on Spinraza.
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