# Preclinical evaluation of a homing endonuclease gene therapy for adRP in models of P23H retinopathy.

> **NIH NIH R01** · UNIVERSITY OF LOUISVILLE · 2024 · $568,819

## Abstract

Autosomal dominant Retinitis pigmentosa (adRP) is a blinding eye disease that results in loss of rods and
eventually cone photoreceptors. A large fraction of adRP is caused by mutations in the rhodopsin (Rho) gene,
and the most common mutation in North America causes a P23H mutation in rhodopsin. Patients typically
present with mid- to late-stage disease when many rod photoreceptors already have degenerated.
We will evaluate genome editing using a meganuclease genome editing tool (Rho1-2) that is specific for the
sequence causing the P23H mutation in several preclinical animal models of P23H adRP. We will deliver AAV5-
GRK1-Rho1-2 via subretinal injection to infect photoreceptors. We will measure efficacy, the ability of Rho1-2 to
alter rod degeneration and functional decline. We will quantitatively determine Rho1-2 efficiency, the proportion
of P23H alleles with insertions/delections (indels), specificity the proportion of P23H to WT alleles with indels,
and its safety, the absence of indels in other genes throughout the human genome (off target editing).
In Pig P23H adRP models we will evaluate Rho1-2 editing efficacy because of the similarities between pigs and
humans in eye size and retinal structure and because the pig has a cone rich visual streak. We will use the same
non-invasive tools used in the clinic to measure retinal function (full field electroretinograms) and structure,
(spectral domain OCT). We will use two existing transgenic pig lines that harbor the entire P23H hRHO gene,
but differ in their time course, resulting in a fast or slow loss of rods and rod function. We will match treatment
time with the natural history of rod structural and functional decline, compare Rho1-2 editing efficacy in early-,
mid- and late-stage P23H adRP and define its temporal treatment window. In Humanized adRP mouse models
we will evaluate Rho1-2 editing efficiency and specificity because they contain WT and P23H human alleles in
the appropriate genomic context. In human retinal organoids we will evaluate Rho1-2 editing safety (off-target
cutting throughout the genome) because they contain human photoreceptors as well as the rest of the human
genome in a relevant context..
Taken together the results of our experiments will determine if Rho1-2 should move forward for eventual use in
human clinical trials and will define endpoints for those trials.

## Key facts

- **NIH application ID:** 10796834
- **Project number:** 5R01EY032645-02
- **Recipient organization:** UNIVERSITY OF LOUISVILLE
- **Principal Investigator:** RONALD G GREGG
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2024
- **Award amount:** $568,819
- **Award type:** 5
- **Project period:** 2023-03-01 → 2028-02-29

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10796834

## Citation

> US National Institutes of Health, RePORTER application 10796834, Preclinical evaluation of a homing endonuclease gene therapy for adRP in models of P23H retinopathy. (5R01EY032645-02). Retrieved via AI Analytics 2026-06-12 from https://api.ai-analytics.org/grant/nih/10796834. Licensed CC0.

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