Spinal Muscular Atrophy Type 3

This double-blind, Phase 2, multiple-dose study will be conducted to evaluate the PK/PD, efficacy, safety, and tolerability of apitegromab in subjects \<2 years old with 5q autosomal recessive SMA who have delayed motor milestones for their age attributed to SMA at the discretion of the Investigator or a Children's Hospital of Philadelphia Infant Test of Neuromuscular Disorders (CHOP-INTEND) score \<55.

The purpose of this research is (1) to identify disease specific walking-related digital biomarkers of disease severity, and (2) monitor longitudinal changes in natural environments, for extended periods of time, in DMD and SMA.

The objective of this study is to understand how spatiotemporal and kinetic gait parameters are associated with bone health in pwSMA who are receiving DMT. We hypothesize that gait parameters are associated with BMD and can determine fracture risk in pwSMA. This is an observational study that involves one in-clinic visit (approximately 3 hours) with remote follow-up visits (approximately 15 minutes) every 3 months for 1 year to collect fracture and medical history. Each of the assessments included in this study are non-interventional and are not intended as a treatment nor are they at the level of standard of care.

The study will evaluate safety and efficacy of intrathecal delivery of GC101 gene therapy drug as a treatment of spinal muscular atrophy Type 3 (SMA 3) patients.