Inclusion  Symptomatic SMA diagnosis based on gene mutation analysis with bi-allelic survival motor neuron 1 (SMN1) mutations (deletion or point mutations) and any copy of the survival motor neuron 2 (SMN2) gene. Weight ≥ 8.5 kg and ≤ 21 kg at the time of Screening Visit 2 Naive to treatment or have discontinued an approved drug/therapy  Exclusion:  Previous OAV101 use or previous use of any AAV9 gene therapy Body Mass Index (BMI) < 3rd percentile based on World Health Organization (WHO) Child Growth Standard Participant with history of aspiration pneumonia or signs of aspiration (eg, coughing or sputtering of food) within 4 weeks prior to screening Anti-Adeno-associated virus serotype 9 (AAV9) antibody titer > 1:50 as determined by ligand binding immunoassay at the time of screening History of gene therapy, hematopoietic transplantation, or solid organ transplantation