SOD1 and proximal spinal muscular atrophy: ,3,4,5 The central nervous system (CNS) has emerged as a crucial target area for ASO therapies, with two landmark approvals for neurodegenerative diseases: nusinersen for spinal muscular atrophy and tofersen for amyotrophic lateral sclerosis caused by the superoxide dismutase 1 (SOD1) gene mutations.6