The Revised Hammersmith Scale (RHS) is a 36 item clinical assessment of physical abilities in patients with Type 2 SMA and ambulatory or nonambulatory patients with Type 3 SMA. For the ambulatory Type 3 patients 5-21 years of age in Cohort 1 (N=23), the primary endpoint was the change from baseline in RHS total score at month 12. The RHS has a minimum achievable score of 0 and a maximum achievable score of 69. The RHS includes 33 items that are graded on a scale of 0, 1, 2, where 0 denotes the lowest level and 2 denotes the highest level of ability/function. The remaining 3 items are scored 0 or 1, where 0 denotes an inability and 1 denotes an ability to achieve. Higher scores indicate increased motor function. A positive change from Baseline indicates improvement.

Cohort 2: For the nonambulatory Type 2 and Type 3 patients 5-21 years of age in Cohort 2 (N=15), the primary efficacy endpoint was the change from baseline in HFMSE total score at month 12. Cohort 3: For the nonambulatory Type 2 patients ≥2 years of age in Cohort 3 (N=20), the primary efficacy endpoint was the change from baseline in HFMSE total score at month 12. The Hammersmith Functional Motor Scale Expanded (HFMSE) assesses the physical abilities of patients with Type 2 and Type 3 SMA comprises 33 items graded on a scale of 0, 1, or 2, where 0 denotes unable, 1 denotes performed with modification or adaptation, and 2 denotes performed without modification or adaptation.