Although the NeuN protein level in the striatum of HD KI‐140Q mice was not changed by intravenous administration of SM3 (Figure S5d,e, Supporting Information), the intensity of GFAP (Figure S5d,e, Supporting Information) and Iba1 (Figure S5d,e, Supporting Information) labeling on western blots was significantly reduced in HD mice after intravenous injection of SM3. This evidence concerns the gene RBFOX3 and Huntington disease.