SMN2 and proximal spinal muscular atrophy: Currently, there are three different drugs approved by the FDA for treatment of SMA [131]: risdiplam, which modulates the splicing of SMN2; onasemnogene abeparvovec, a non-replicating adeno-associated virus capsid delivering a SMN1 copy; and nusinersen, which is an antisense oligonucleotide increasing the protein level of SMN by modulating the splicing of SMN2-mRNA [132].