Better Survival Trends Seen With Spinraza in SMA Children in Sweden

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by Marta Figueiredo PhD |

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The introduction of Spinraza (nusinersen) as a treatment for spinal muscular atrophy (SMA) in Sweden was associated with trends of improved survival in children diagnosed with the disease before they were 2 years old, a nationwide population-based study shows.

While these trends did not reach statistical significance relative to the period before Spinraza, children receiving the therapy had a significantly lower risk of death compared with untreated children.

These real-world findings add to clinical trial data showing that Spinraza prolonged survival in children with the severe SMA type 1, the researchers noted.

The study, “Survival in patients diagnosed with SMA at less than 24 months of age in a population-based setting before, during and after introduction of nusinersen therapy. Experience from Sweden,” was published in the European Journal of Paediatric Neurology.

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Biogen’s Spinraza was the first disease-modifying therapy (DMT) approved for all SMA types. Administered directly into the spinal canal, it works by increasing the production of the SMN protein, whose deficiency causes SMA.

In a previous Phase 3 clinical trial (NCT02193074), the therapy was shown to significantly prolong the survival and improve the motor function of children with type 1 disease.

This severe form is characterized by a symptom onset at up to 6 months of age and a median life expectancy of less than 2 years without respiratory support.

“However, there is a lack of data outside clinical trials on how the introduction of [Spinraza] has affected the survival of patients with SMA,” the researchers wrote.

With this in mind, a team of researchers in Sweden analyzed the survival of children diagnosed with SMA before 2 years of age before, during, and after Spiranza’s introduction.

Analysis includes 155 children from the Swedish National Patient registry

Eligible patients were identified through the Swedish National Patient registry — which includes all people with an inpatient diagnosis — between Feb. 21, 2000 and Dec. 19, 2019. Medical records, including treatment with Spinraza, were linked to the Swedish Cause of Death Registry to assess their vital status.

The selective inclusion of children diagnosed at 2 years or younger was expected to increase the proportion of type 1 patients in the analysis, the team noted.

Data were divided into three time periods. The first period, when no SMA DMT was available in the country, ranged from Feb. 21, 2000 to Sept. 22, 2015.

Period 2, when Spinraza was available to patients only through clinical trials and an early access program, ran from Sept. 23, 2015, to Dec. 21, 2017. The last period, from Dec. 22, 2017, to Dec. 31, 2019 (study data cutoff), represented the time after the therapy’s approval and recommendation for use in Sweden.

A total of 155 patients (79 girls and 76 boys) were included in the analysis: 115 in period 1, 21 in period 2, and 19 in period 3. About a quarter of them (42 children; 27.1%) were diagnosed with SMA after 1 year of age.

Follow-up clinical data were collected for a median of 1.14 years, and 26 children initiated Spinraza treatment: 14 (66.7%) during the period of its limited availability and 12 (63.2%) after its approval.

Results showed that survival estimates for children diagnosed during and after Spinraza’s introduction were slightly better than those before the therapy’s introduction. This reflected a reduced risk of death by about 30% in children in periods 2 and 3 relative to those in period 1. However, none of these differences reached statistical significance.

In addition, during and after Spinraza’s introduction, 12 (85.7%) of the 14 children who did not receive any DMT died versus one (3.85%) of the 26 children treated with Spinraza. This meant that Spinraza significantly reduced the risk of death by 95%.

A similar survival benefit was detected when restricting the analysis to children diagnosed before 1 year of age — which could include a higher proportion of type 1 patients.

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“In conclusion, we found no evidence of differences in overall survival between the three calendar periods,” the researchers wrote.

“However, SMA patients that were defined as receiving [Spinraza] had a dramatically increased overall survival which also indicates that [Spinraza] has an effect on survival, in patients diagnosed with SMA, in a nationwide real-world setting,” the team added.

The study was funded by a grant from Biogen. Two of the four study authors were current or former employees of Biogen Sweden, while the remaining two were consultants or have been on advisory boards for the company.

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