Preclinical studies of gene replacement therapy for CDKL5 deficiency disorder
Gregory Voronin1, Jana Narasimhan1, Jamila Gittens1
1PTC Therapeutics, Inc, 500 Warren Corporate Center Drive, Warren, NJ 07059, USA.
Abstract:
Cyclin-dependent kinase-like 5 (CDKL5) deficiency disorder (CDD) is a rare neurodevelopmental disorder caused by a mutation in the X-linked CDKL5 gene. CDKL5 is a serine/threonine kinase that is critical for axon outgrowth and dendritic morphogenesis as well as synapse formation, maturation, and maintenance. This disorder is characterized by early-onset epilepsy, hypotonia, and failure to reach cognitive and motor developmental milestones. Because the disease is monogenic, delivery of the CDKL5 gene to the brain of patients should provide clinical benefit. To this end, we designed a gene therapy vector, adeno-associated virus (AAV)9.Syn.hCDKL5, in which human CDKL5 gene expression is driven by the synapsin promoter. In biodistribution studies conducted in mice, intracerebroventricular (i.c.v.) injection resulted in broader, more optimal biodistribution than did intra-cisterna magna (i.c.m.) delivery. AAV9.Syn.hCDKL5 treatment increased phosphorylation of EB2, a bona fide CDKL5 substrate, demonstrating biological activity in vivo. Our data provide proof of concept that i.c.v. delivery of AAV9.Syn.hCDKL5 to neonatal male Cdkl5 knockout mice reduces pathology and reduces aberrant behavior. Functional improvements were seen at doses of 3e11 to 5e11 vector genomes/g brain, which resulted in transfection of ≥50% of the neurons. Functional improvements were not seen at lower doses, suggesting a requirement for broad distribution for efficacy.
Insights
Gene therapy using AAV9.Syn.hCDKL5 shows promise for Cyclin-dependent kinase-like 5 (CDKL5) deficiency disorder (CDD). Intracerebroventricular delivery in mice improved pathology and behavior, demonstrating potential for treating this rare neurodevelopmental condition.
Area of Science:
- Neuroscience
- Genetics
- Molecular Biology
Background:
- Cyclin-dependent kinase-like 5 (CDKL5) deficiency disorder (CDD) is a rare neurodevelopmental condition.
- Mutations in the CDKL5 gene cause CDD, impacting brain development and function.
- CDKL5 is crucial for neuronal development, including axon growth and synapse formation.
Purpose of the Study:
- To develop and test a gene therapy vector for CDD.
- To evaluate the efficacy of adeno-associated virus (AAV)9.Syn.hCDKL5 delivered intracerebroventricularly (i.c.v.) in a mouse model of CDD.
Main Methods:
- Designed an AAV9 vector expressing the human CDKL5 gene under the synapsin promoter (AAV9.Syn.hCDKL5).
- Administered AAV9.Syn.hCDKL5 via i.c.v. injection in neonatal male Cdkl5 knockout mice.
- Assessed biodistribution, biological activity (EB2 phosphorylation), pathology, and behavioral outcomes.
Main Results:
- Intracerebroventricular delivery of AAV9.Syn.hCDKL5 resulted in broader biodistribution compared to other methods.
- Treatment demonstrated biological activity by increasing phosphorylation of a CDKL5 substrate (EB2).
- Functional improvements and reduced pathology were observed at specific vector genome doses, requiring broad neuronal transfection.
Conclusions:
- Intracerebroventricular delivery of AAV9.Syn.hCDKL5 provides a proof of concept for CDD gene therapy.
- Broad distribution of the gene therapy vector is essential for functional recovery in CDD models.
- This approach holds potential for treating patients with CDKL5 deficiency disorder.
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