Interestingly, CDKL5 is probably the most studied among such “dark kinases” (i.e., poorly understood kinases) [10,11] mainly due to the relevance of this protein in neuronal development and its involvement in an infantile neurodevelopmental disorder named CDKL5 deficiency disorder (CDD) [12,13]. This evidence concerns the gene CDKL5 and neurodevelopmental disorder.