SMN1 and proximal spinal muscular atrophy: Studies testing the therapeutic potential of a histone deacetylase inhibitors (valproic acid) on human cell lines, did not show significant changes in SMN-FL levels after treatment (61), while in a corresponding phase 2 trial with valproic acid in children and adolescents SMA patients of all types, SMN2-FL levels were unchanged while SMN-D7 levels were significantly reduced (62).