Statistical analysis
The sample size in this study was determined from the participants who completed the initial 24-week study and enrolled into the LTE study. Therefore, the sample size was not based on any statistical considerations. Statistical considerations and power to detect statistical differences were aligned with the initial 24-week study [All timed function tests were performed using the full analysis set (FAS), which included all participants who received≥1 dose of viltolarsen in both the initial 24-week study and LTE study. The safety population, which was the primary analysis population for safety assessments, was identical to the FAS. Efficacy outcome measures were tested between study participants and the CINRG DNHS control group using a mixed-effects linear model. All statistical tests were two-sided and performed at a significance level of 0.05 using SAS v9.4 or higher.