• Male or female newborn infant aged \<20 days at first dose

• Newborn infants with genetic diagnosis of 5q-autosomal recessive SMA or newborn infants identified as positive for SMA via newborn screening or via prenatal testing.

• Gestational age equal to or greater than 37 weeks

• Receiving adequate nutrition and hydration at the time of screening

• Adequately recovered from any acute illness at baseline and considered well enough to participate in the study

• Parent/caregiver is willing to consider nasogastric, nasojejunal, or gastrostomy tube placement during the study to maintain safe hydration, nutrition, and treatment delivery, if recommended by the investigator.