HDAC6 and neuroblastoma: In order to confirm the dual inhibitory activity of C11 on GSK-3β and HDAC6, we treated a recently generated human neuronal cell model of CDKL5 deficiency, the CDKL5 knockout (KO) SH-SY5Y neuroblastoma cell line (SH-CDKL5-KO; [19]), with C11 (1 and 10 μM), and, as a control for selective GSK-3β inhibition, with NP-12 (Tideglusib; 1 μM).