A Study to Evaluate How Apitegromab Works in Subjects Who Are Less Than 2 Years Old and Have Spinal Muscular Atrophy

Prior treatment

• Major orthopedic issues such as severe scoliosis or severe contractures or interventional procedure, including spine or hip surgery, which is considered to have the potential to substantially limit the ability of the subject to be evaluated on any motor function outcome measures, within 6 months before Screening or anticipated during the study.

Other

• Nutritional status that is not anticipated to be stable throughout the study or medical necessity for a gastric feeding tube, where most feeds are administered by this route, as assessed by the Investigator and/or an Oral and Swallowing Abilities Tool score of 0.
• Any other physical limitations (eg, the subject requires cast for contractures) that would prevent the subject from undergoing motor function outcome measures throughout the study.
• Has a sibling participating in this study (ie, only 1 subject per immediate family is allowed to participate in the study)
• Subject is breastfeeding while the mother is taking barbiturates and/or opioids

• Is <2 years old at the time of the informed consent
• Had a gestational age of ≥35 weeks and gestational body weight ≥2.0 kg at birth
• Has confirmed diagnosis of 5q autosomal recessive SMA
• Has confirmed presence of SMN2 gene copy(ies)
• Must have been treated with an approved SMN1-targeted therapy (ie, onasemnogene abeparvovec-xioi) or are continuing to be treated with an approved SMN2-targeted therapy (ie, nusinersen or risdiplam)
• Body weight for age is no less than third percentile based on the WHO Child Growth Standards at the Screening Visit
• Has delayed motor milestones for age attributed to SMA at the discretion of the Investigator or a CHOP-INTEND score <55.