To overcome these issues, the latest research is trying to identify better antisense chemistries. Administration of phosphorodiamidate morpholino oligomers (PMOs) targeting ISS-N1 by a single intracerebroventricular injection ameliorated the SMA symptom in the mouse models17. An 8-mer 2′OMeP AONs with PEG-282 and propyl modifications at the 5′ and 3′ ends also improved the phenotypes of SMA mouse models18. Recently, it has been demonstrated that peptide-conjugated PMOs (Pip6a-PMOs) were delivered to the central nervous system (CNS) by intravenous injections and rescued the phenotype of a severe SMA mouse model19. However, no clinical trial has been reported with these chemistries for SMA.