# A cross-correction gene therapy approach for CDKL5 deficiency disorder improves the pathological phenotype of CDD patient-derived cortical organoids

## TL;DR

A new gene therapy approach using a modified CDKL5 protein improves symptoms in a human model of CDKL5 Deficiency Disorder.

## Contribution

A novel cross-correction gene therapy using a secretable TATk-CDKL5 protein shows superior efficacy in treating CDKL5 Deficiency Disorder.

## Key findings

- The TATk-CDKL5 protein outperformed conventional CDKL5 in correcting CDD-related defects in cortical organoids.
- TATk-CDKL5 restored abnormal hyperexcitability and neuronal cell death in CDD patient-derived organoids.
- The cross-correction approach improved proliferation and survival of neurons in the organoid model.

## Abstract

Efficient delivery of biological material to the central nervous system remains a key limitation of conventional gene therapies. Recently, we developed a novel strategy based on a secretable and cell-penetrating TATk-CDKL5 fused protein which enhances the brain biodistribution and the therapeutic efficiency of the gene therapy approach in a mouse model of CDKL5 Deficiency Disorder (CDD). Here, to compare the efficacy of the TATk-CDKL5 gene therapy with a conventional approach in correcting the CDKL5 Deficiency Disorder pathological phenotype, we employed cortical organoids generated from CDD patient-derived iPSCs as a human model of CDD. We found greater therapeutic efficacy of the recombinant TATk-CDKL5 protein compared to the CDKL5 protein alone in improving or ameliorating defects caused by the absence of CDKL5, such as abnormal hyperexcitability evaluated with microelectrode arrays (MEA). Interestingly, CDD cortical organoids exhibited reduced cell proliferation and increased neuronal cell death compared to control cortical organoids; defects that were only restored by the expression of the recombinant TATk-CDKL5 protein. Based on the results from phenotypic and functional readouts, these findings suggest that gene therapy using a cross-correction approach offers superior efficiency in treating CDD.