SMN2 and proximal spinal muscular atrophy: However, a previous study on non-human primates and piglets following IV administration of an AAV9 variant encoding SMN, and a more recent study conducted in a severe mouse model of SMA is instructive for understanding potential long-term consequence of the AAV9-mediated gene therapy of SMA (Hinderer et al., 2018; Van Alstyne et al., 2021).