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

Clinical trials have demonstrated a positive effect of nusinersen therapy on survival of infants with SMA type 1. However, there is a lack of data outside clinical trials on how the introduction of nusinersen has affected the survival of patients with SMA. We therefore set out to analyse survival in patients diagnosed at less than 24 months before, during and after the introduction of nusinersen in a nationwide population-based real-world setting.SMA patients diagnosed before the age of 24 months in the time period between February 21, 2000 and December 19, 2019 were identified using ICD-codes, and medical procedures for identification of treatment utilizing information from the public available National Patient Registry held by the National Board of Health and Welfare. Data was divided into 3 different calendar periods (before, during, and after introduction of nusinersen treatment in Sweden). Time to Event analysis was then applied.A total of 155 patients were enrolled in the study, and median follow-up was 1.14 years (inter-quartile range (IQR): 0.27-8.37 years). Data did not provide conclusive evidence that survival differed between the calendar periods (P-value from the log-rank test = 0.419) and while hazards were lower in the middle period, HR 0.70 (95% CI: 0.34-1.47), and 3, HR 0.71 (95% CI: 0.28-1.77) compared to the first period, all confidence intervals were wide., However, nusinersen treatment was associated with a decreased mortality rate, HR 0.05 (95% CI: 0.01-0.37).SMA patients receiving nusinersen therapy had a dramatically increased overall survival compared to patients not receiving therapy. This indicates that nusinersen treatment has an effect on survival, in patients diagnosed with SMA, in a nationwide real-world setting. Larger studies are warranted.