The follow-up phase 3 trials, STR1VE-US (NCT03306277) and STR1VE-EU (NCT03461289), treated children < 6 months of age with SMA type I and up to two copies of SMN2 with the high dose used in the START trial [21,26,27]. Here, SMN2 is linked to spinal muscular atrophy, type 1.