CDKL5 and neuroblastoma: In order to investigate whether treatment with P021 rescued CDD-related phenotypes we used a human neuronal cell model of CDKL5 deficiency, the CDKL5 knockout (KO) SH-SY5Y neuroblastoma cell line (SH-CDKL5-KO; [20]), which shows impaired cell proliferation and survival, and deficit in neuronal maturation [20].