A Study of Multiple Doses of Nusinersen (ISIS 396443) Delivered to Infants With Genetically Diagnosed and Presymptomatic Spinal Muscular Atrophy

• Age ≤ 6 weeks at first dose.
• Genetic documentation of 5q SMA homozygous gene deletion or mutation or compound heterozygous mutation.
• Genetic documentation of 2 or 3 copies of survival motor neuron 2 (SMN2).
• Ulnar compound muscle action potential (CMAP) ≥ 1 mV at Baseline.
• Gestational age of 37 to 42 weeks for singleton births; gestational age of 34 to 42 weeks for twins.
• Meet additional study related criteria.

• Hypoxemia (oxygen saturation <96% awake or asleep without any supplemental oxygen or respiratory support).
• Any clinical signs or symptoms at Screening or immediately prior to the first dosing (Day 1) that are, in the opinion of the Investigator, strongly suggestive of SMA.
• Clinically significant abnormalities in hematology or clinical chemistry parameters.
• Treatment with an investigational drug given for the treatment of SMA biological agent, or device. Any history of gene therapy, prior antisense oligonucleotide (ASO) treatment, or cell transplantation.
• Meet additional study related criteria.

Note: Other protocol defined Inclusion/Exclusion criteria may apply.