New hope for SMA babies: boosting gene therapy with a Follow-Up drug

Copied word for word from the study's registry entry, so the wording is the study team's rather than ours.

Key Inclusion Criteria: * Genetic documentation of 5q spinal muscular atrophy (SMA) homozygous gene deletion or mutation or compound heterozygous mutation. * 2 copies of the survival motor neuron 2 (SMN2) gene. * Onasemnogene Abeparvovec (OA) dose given at ≤ 42 days of age and screening initiated less than 6 months from OA dosing. * OA dose given while participant was presymptomatic, per Investigator attestation. For this study, presymptomatic is defined as follows: * No clinical signs or symptoms at the time of OA dosing that are, in the opinion of the Investigator, strongly suggestive of SMA. * No absence of tendon reflexes (i.e., absence of all of biceps, knee and ankle tendons) at the time of OA dosing (e.g., Hammersmith Infant Neurological Examination (HINE) Section 1 or equivalent). * If Compound Muscle Action Potential (CMAP) data is available at the time of dosing, ulnar CMAP amplitude ≥ 2 millivolt (mV). Key Exclusion Criteria: * Any unresolved post-OA laboratory abnormalities defined as follows: * Alanine aminotransferase (ALT) or aspartate aminotransferase (AST) must be less than 2 × Upper Limit of Normal (ULN) while not receiving corticosteroids within 30 days prior to dosing with salanersen or sham procedure (repeat testing may be performed if necessary). * Evidence of thrombocytopenia, indicated by the platelet count being lower than the normal range for the laboratory. * Evidence of elevated troponin-I levels, identified as elevated post-OA, and has not returned to the normal range. * Confirmed demonstration of corrected QT interval, using Fridericia's correction method, of \> 450 milliseconds (ms). * Other than OA, any prior treatment with an approved SMA disease modifying therapy (e.g. nusinersen and/or risdiplam), a myostatin inhibitor therapy, or an investigational drug given for the treatment of SMA. * Steroid treatment administered for the purpose of treating complications following OA within 14 days prior to dosing with salanersen or sham procedure on Day 1. Note: Other protocol-defined inclusion/exclusion criteria will apply.