Prof. Rotem Karni
Background:
• PCDH19-CE / EIEE-9 is a rare neurodevelopmental disorder with severe and repeated epileptic seizures, neurocognitive and neuropsychiatric disabilities, autism spectrum characteristics, and other comorbidities.
• No disease-specific treatment is currently available beyond supportive care, and many patients are resistant to available anti-epileptic drugs.
• Patient population is estimated at approximately 1,000-2,000 patients with PCDH19 mutations in the US, based on the provided estimates for Dravet syndrome and PCDH19 contribution.
Our Innovation:
• Targeted PCDH19 silencing: our therapeutic strategy uses GAPmer antisense oligonucleotides to bind PCDH19 mRNA and trigger RNase H-mediated transcript degradation, thereby reducing PCDH19 expression.
• Disease-model rationale: the approach is based on the observation that the severe phenotype is linked to heterozygous/mosaic PCDH19 expression, while complete loss of PCDH19 appears clinically preferable to the heterozygous state.
• Human neuronal model: we generated female human ES cells carrying a PCDH19 nonsense knock-in mutation across WT, heterozygous, and homozygous genotypes and differentiates them into neurons using an inducible NGN2/ASCL1 system.
• Lead discovery work: a screen of 20 PCDH19-targeting GAPmers identified five that reduced PCDH19 levels by at least 80% in human cell lines, and a selected GAPmer achieved approximately 60% Pcdh19 mRNA knockdown with reduced protein expression in mouse brain after ICV administration.
Advantages:
• Measurable human-cell phenotype: heterozygous PCDH19-mutant induced neurons showed significantly shorter neurite lengths and a significantly lower astrocyte ratio compared with WT and homozygous mutant cells.
• Genotype-specific biology: WT and homozygous/hemizygous models show similar patterns, while heterozygous female models show distinct molecular and cellular defects, matching the disease-relevant mosaic state.
• Built-in development readouts: RNA-seq, proteomics, phosphoproteomics, Q-RT-PCR, Western blot, immunofluorescence, neurite length, astrocyte quantification, and MEA neuronal activity assays are planned to evaluate disease phenotype and response to PCDH19 knockdown.
• Multiple therapeutic paths: the project includes ASO knockdown and downstream-target/gene-therapy approaches, with splice-switching oligonucleotides identified as an alternative PCDH19 down-regulation strategy.
Commercial Opportunity:
• We are seeking collaboration with biopharmaceutical, rare disease, epilepsy, and oligonucleotide-therapy companies to co-develop a PCDH19-targeting ASO/GAPmer program, validate rescue of molecular, cellular, and neuronal activity phenotypes in human models, and advance a targeted therapeutic approach for PCDH19-CE.
