human Rhodopsin / Kubota - LARVOL DELTA

Subretinal injection in the USH1CR31* pig model leads to chorioretinal atrophy that limits evaluation of efficacy of an AAV-mediated gene therapy. (PubMed, Exp Eye Res) - "USH1CR31* and wild type (WT) pigs were bilaterally subretinal injected with 200 μl of 1*1011 vg/eye Anc80 AAV vectors expressing USH1C_a1 under the control of either a rod-specific human rhodopsin kinase (GRK1) promoter, a ubiquitous promoter (CAG), or vehicle control...Decreased ERG amplitudes and reduction of total retinal thickness were observed in all groups following surgery...The extensive retinal damage associated with CRA has likely masked a potentially beneficial therapeutic effect. For future translational development, optimization of dosing, and modifications in surgical technique will be of crucial importance."

Journal • Preclinical • Gene Therapies • Inherited Retinal Dystrophy • Ophthalmology • FAP • GFAP

Nonclinical efficacy and toxicity study of GMP-grade vector OPGx-RHO (scAAV2/5-RHO820-shRNA820) delivered by subretinal injection in a canine model of RHO-adRP. (ASGCT 2026) - "Proof of concept studies in a naturally occurring dog model of adRP, the closest disease model representative of human rhodopsin-mediated adRP, caused by a mutation in the RHO gene have recently shown that a knockdown and replacement gene therapy strategy confers protection to photoreceptors (both anatomic and functional) preventing retinal degeneration...The mid and high doses of the test-article conferred structural preservation of the ONL and IS/OS, as assessed by OCT imaging and histology. Conclusion These findings define the no-observed-adverse-effect-level (NOAEL) as the mid-dose of OPGx-RHO: 4.74 x 1010 vg/eye (3.6 × 1011 vg/mL)."

Clinical • Preclinical • Gene Therapies • Genetic Disorders • Inflammation • Inherited Retinal Dystrophy • Ocular Inflammation • Ophthalmology • Retinal Disorders • Retinitis Pigmentosa

Characterizing the interactome of human P23H rhodopsin using stem cell derived retinal organoids (ARVO 2026) - "Methods We aim to assess the proteins interacting with human rhodopsin by comparing RHO pull-down lysates from RHO+/+ wildtype and RHOP23H/+ diseased human stem cell-derived retinal organoids...Currently, there are no therapies available for RHOP23H induced adRP, therefore understanding rhodopsin interaction in human tissue (lab grown retinal organoids) might reveal potential binding partners of therapeutic interest. The findings from our research will be informative to understand the cellular response pathways activated in retinal organoids during disease state and help identify strategies to degrade mutant RHOP23H protein to prevent blindness."

Inherited Retinal Dystrophy • Ocular Inflammation • Ophthalmology • Retinal Disorders • Retinitis Pigmentosa

Zebrafish Functional Screening of FDA-Approved Drugs for Autosomal Dominant Retinitis Pigmentosa Caused by RHODOPSIN Q344X Mutation. (PubMed, bioRxiv) - "To address this challenge, we screened an FDA-approved compound library using a zebrafish adRP model expressing a human RHODOPSIN transgene with the Q344X mutation...Four compounds significantly improved VMR in Q344X zebrafish: amitriptyline, difluprednate, maprotiline, and prednisolone. Further characterization revealed that these hits act through distinct mechanisms, including reducing rod death, promoting rod neogenesis, and enhancing the function of extraocular photoreceptors. Together, these findings demonstrate the potential to repurpose these drugs for adRP caused by the RHO Q344X mutation, providing preclinical candidates and revealing potential targets for future drug development."

FDA event • Journal • Genetic Disorders • Inherited Retinal Dystrophy • Ocular Inflammation • Ophthalmology • Retinal Disorders • Retinitis Pigmentosa

Cis- and Trans-Regulatory Factors Independently Shape Phenotypic Heterogeneity of Retinitis Pigmentosa. (PubMed, Adv Sci (Weinh)) - "In this study, we identified two distinct genetic mechanisms influencing RP severity using a transgenic zebrafish model expressing the human rhodopsin S334X mutation...Together, these findings provide the first in vivo evidence that both cis- and trans-regulatory elements independently and cooperatively modulate RP phenotypes within a shared genetic background. They clearly establish the existence of genetic modifiers as key contributors to disease variability, offering new directions for personalized RP management."

Heterogeneity • Journal • Genetic Disorders • Inherited Retinal Dystrophy • Ocular Inflammation • Ophthalmology • Retinal Disorders • Retinitis Pigmentosa

Advantages of human opsins in optogenetic visual restoration. (PubMed, Front Neurosci) - "Bistable melanopsin enables durable irradiance coding but with slow dynamics; chimeric designs (e.g., melanopsin-mGluR6, Gloeobacter-human rhodopsin) aim to combine amplification with favorable reset properties...Pharmacological noise suppression in degenerating retinas (e.g., gap-junction blockers or retinoic-acid pathway modulators) may further enhance signal-to-noise without altering opsin biochemistry. Together, these steps can move human-opsin optogenetics from experimental promise to clinically meaningful restoration of light sensitivity."

Journal • Review • CNS Disorders • Gene Therapies • Inflammation • Ocular Inflammation • Ophthalmology

Aggregation of the Constitutively Active K296E Rhodopsin Mutant Contributes to Retinal Degeneration. (PubMed, FASEB J) - "The K296E mutation on either murine or human rhodopsin backgrounds exhibited similar propensities to aggregate. The same mutation on a bovine rhodopsin background, however, exhibited a lower propensity to aggregate, indicating this species background does not adequately model the effects of the K296E mutation. In contrast to previous expectations, we demonstrate here that aggregation of the K296E rhodopsin mutant may contribute to photoreceptor cell loss in retinitis pigmentosa."

Journal • Genetic Disorders • Inherited Retinal Dystrophy • Ocular Inflammation • Ophthalmology • Retinal Disorders • Retinitis Pigmentosa

Active and inactive pathways in the kinetic mechanism of the G51V retinitis pigmentosa mutant photoreaction. (PubMed, Biophys J) - "While studies of the WT protein yielded a mechanism consistent with previous determinations of human rhodopsin (15), the G51V mechanism involved multiple pathways. These results suggest multiple ways for the protein to fold, some of which are photoactivated while the majority do not activate normally."

Journal • Genetic Disorders • Inherited Retinal Dystrophy • Ocular Inflammation • Ophthalmology • Retinal Disorders • Retinitis Pigmentosa

Aggregation of the constitutively active K296E rhodopsin mutant contributes to retinal degeneration. (PubMed, bioRxiv) - "The K296E mutation on either murine or human rhodopsin backgrounds exhibited similar propensities to aggregate. The same mutation on a bovine rhodopsin background, however, exhibited a lower propensity to aggregate, indicating this species background does not adequately model the effects of the K296E mutation. In contrast to previous expectations, we demonstrate here that aggregation of the K296E rhodopsin mutant can promote photoreceptor cell loss."

Journal • Genetic Disorders • Inherited Retinal Dystrophy • Ocular Inflammation • Ophthalmology • Retinal Disorders • Retinitis Pigmentosa

Investigating Utility of Three Dimensional Hydrodynamic Parameters to Predict mRNA Target Site Accessibility for Nucleic Acid Drugs (ARVO 2025) - "Methods Human rhodopsin (RHO) mRNA was used as a model target RNA as there is substantial experimental data on efficacy of ribozymes and shRNAs as knockdown (KD) agents...Layman Abstract (optional): Provide a 50-200 word description of your work that non-scientists can understand. Describe the big picture and the implications of your findings, not the study itself and the associated details."

Ophthalmology

Evaluation of AAV-Mediated Optogenetic Expression in Human Retinal Organoids (ARVO 2025) - "AAV-mediated human rhodopsin expression in retinal organoids did not affect HRO' viability, indicating good initial safety data for this optogene for further translational studies. Layman Abstract (optional): Provide a 50-200 word description of your work that non-scientists can understand. Describe the big picture and the implications of your findings, not the study itself and the associated details."

Ophthalmology • Retinal Disorders

Enhanced hammerhead ribozyme turnover rates: Reevaluating therapeutic space for small catalytic RNAs. (PubMed, Mol Ther Nucleic Acids) - "We discovered enhanced hammerhead ribozyme (EhhRz) kinetic performance during therapeutic optimization of a lead agent against the human rhodopsin mRNA target...Embedded within a target-reporter fusion mRNA, EhhRzs cleave regional target elements under intracellular conditions promoting strong knockdown at target mRNA and protein levels. EhhRzs have potential as druggable nucleic acid therapeutics against arbitrary targets, or in the design of improved aptazymes."

Journal • Gene Therapies

Gene therapy in children with AIPL1-associated severe retinal dystrophy: an open-label, first-in-human interventional study. (PubMed, Lancet) - "Our findings indicate that young children with AIPL1-related retinal dystrophy benefited substantially from subretinal administration of rAAV8.hRKp.AIPL1, with improved visual acuity and functional vision and evidence of some protection against progressive retinal degeneration, without serious adverse effects."

Clinical • Journal • P1 data • Gene Therapies • Inflammation • Inherited Retinal Dystrophy • Macular Edema • Ocular Inflammation • Ophthalmology • Retinal Disorders

Ectopically expressed rhodopsin is not sensitive to X-rays. (PubMed, BMC Neurosci) - "Here we investigate whether human rhodopsin (hRho) is capable of transducing X-ray signals when expressed outside of the retinal environment...Additionally, irradiation had no significant effect on cAMP GloSensor responses to subsequent visible light stimulation. These results suggest that ectopically expressed rhodopsin does not function as an X-ray receptor and is not capable of transducing transcranial X-ray signals into neural activity for X-ray mediated, genetically targeted neuromodulation."

Journal

12-Month Safety and Efficacy Evaluation of HORA-PDE6B, a Gene Therapy Targeting Patients with Retinitis Pigmentosa Due to Biallelic PDE6B Gene Mutation. (ARVO 2024) - "It employs an Adeno-Associated Virus serotype 5 (AAV2/5) vector carrying the human PDE6B isoform 1 cDNA, controlled by the photoreceptor-specific human rhodopsin kinase promoter that targets Rods photoreceptors. Over a short 12-month period, HORA-PDE6B has shown a favorable safety profile and potentially efficacy, encouraging the continued development of HORA-PDE6B."

Clinical • Gene therapy • Inherited Retinal Dystrophy • Ocular Inflammation • Ophthalmology • Retinal Disorders • Retinitis Pigmentosa • Uveitis

Rhodopsin mislocalization disrupts synaptic protein trafficking to rod pre-synaptic spherules in a P23H rhodopsin retinitis pigmentosa mouse model (ARVO 2024) - " We used a combination of structured illumination microscopy (SIM), transmission electron microscopy (TEM), quantitative confocal microscopy, quantitative western blotting, and tandem mass tag spectrometry (TMT) to examine the morphology and synaptic protein expression levels in mutant rods from P23H-hRho-tagRFP-T/+ mice, which have the P23H human rhodopsin gene fused to a RFP, and from rd10 mice. Our results show Rho mislocalization to the presynaptic compartment in both P23H-RFP/+ mice and rd10 mice, but this mislocalization differs between models and impacts the rod spherules differently. Rod synaptic protein expression levels are altered in P23H-RFP/+ mice but not in rd10 mice, which is likely due to mutant P23H-Rho aggregating in the ER and disrupting the normal ER secretory system. Future studies will focus on this under-investigated rod synaptic secretory pathway to determine its role in synaptic protein regulation and RP disease progression."

Preclinical • Inherited Retinal Dystrophy • Ocular Inflammation • Ophthalmology • Retinal Disorders • Retinitis Pigmentosa

The Rho1-2 meganuclease targeted to the human P23H human rhodopsin allele in a transgenic pig model of Autosomal Dominant Retinitis Pigmentosa (adRP) generates wide variety of inactivating mutations. (ARVO 2024) - "Our data show that Rho1-2 meganuclease generates a range of INDELs, whichare predicted to have inactivating mutations that truncate or create deletions in the P23Hprotein. Given rods represent ~ 2% of the cell bodies in the retina at the examined ages, andRho1-2 is only expressed in rods, this suggests that most of the remaining rods carry INDELs inthe P23H transgene, resulting in their long-term survival."

Preclinical • Inherited Retinal Dystrophy • Ocular Inflammation • Ophthalmology • Retinal Disorders • Retinitis Pigmentosa

Multi-modal characterization of P23H rats for preclinical development (ARVO 2024) - "For most RP, a single substitution in the human rhodopsin gene (P23H) is responsible... Our natural history study demonstrated early-onset retina degeneration in HO animals. Degeneration was slower in HE animals but still progressive. Multimodal evaluations confirmed similar trends across evaluation modes."

Preclinical • Inherited Retinal Dystrophy • Ocular Inflammation • Ophthalmology • Retinal Disorders • Retinitis Pigmentosa

Validating human-derived organoids as a suitable model for testing optogenetic therapies (ARVO 2024) - "Using the human retinal organoid model, we were able to assess preliminary expression patterns and impact on the cell viability of optogenetic tools. The efficiency of organoid transduction varies based on the AAV capsid and vector dose. Notably, expression of human rhodopsin in retinal organoids does not affect the viability of retinal organoids, indicating safety of this optogenetic tool for further translational studies."

Inherited Retinal Dystrophy • Ocular Inflammation • Ophthalmology • Retinal Disorders • Retinitis Pigmentosa

Evaluation of mirtron silencing and rhodopsin restoration in a human rhodopsin P23H knock-in mouse model (ARVO 2024) - "In vivo, optimal knockdown of human P23H rhodopsin transcripts was achieved, with concurrent attainment of optimal rhodopsin replacement levels at high and medium doses. Enhancements in inferior retinal thickness were noted in eyes administered the triple mirtron vector at high and medium doses, indicating the prospect of utilizing artificial mirtrons in RNA replacement for retinal gene therapy."

Preclinical • Inherited Retinal Dystrophy • Ocular Inflammation • Ophthalmology • Retinal Disorders • Retinitis Pigmentosa

Enhanced Hammerhead Ribozyme Function in vivo: Developing Therapeutic Space for Catalytic RNAs (ARVO 2024) - "Here, plasmids (bicistronic, fusion RNA) are developed to incorporate the endogenous cleavage site in human rhodopsin mRNA (hRHO) target or multiple cleavage sites embedded in a mCherry reporter to allow efficient quantitative assays to test therapeutic potential... A 41nt synthetic EhhRz cleaves WT hRHO at accessible 266 (CUC↓) in trans. Cleavage of endogenous 266 in hRHO and target elements in UTR regions of a mCherry fusion RNA reporter or bicistronic mRNA strongly suppress target expression. These experiments further develop EhhRz therapeutics for ocular diseases."

Preclinical • Ophthalmology

Scaling up Functional Analyses of the G Protein-Coupled Receptor Rhodopsin. (PubMed, J Mol Evol) - "Using this approach, we measured the mutational effects of over 1200 individual human rhodopsin mutants, generated by low-frequency random mutagenesis of the GPCR rhodopsin (RHO) gene...Lastly, functional scores from our assay were consistent with a complex counterion mechanism involved in ligand-binding and rhodopsin activation. Our results demonstrate that deep mutational scanning is possible for rhodopsin activation and can be an effective method for revealing properties of mutational tolerance that may be generalizable to other transmembrane proteins."

Journal

Highly sensitive visual restoration and protection via ectopic expression of chimeric rhodopsin in mice. (PubMed, iScience) - "To achieve this in retinal gene therapy, we incorporated human rhodopsin cytoplasmic loops into Gloeobacter rhodopsin, thereby generating Gloeobacter and human chimeric rhodopsin (GHCR)...Retinal explant and visual thalamus electrophysiological recordings, behavioral tests, and histological analysis showed that GHCR restored dim-environment vision and prevented the progression of retinal degeneration. Thus, GHCR may be a potent clinical tool for the treatment of retinal disorders."

Journal • Preclinical • Gene Therapies • Ophthalmology • Retinal Disorders

Lysine Ubiquitylation Drives Rhodopsin Protein Turnover. (PubMed, Adv Exp Med Biol) - "We transfected HEK293 cells with a P23H human rhodopsin construct where all 11 lysine residues were mutated to arginine (K-null P23H)...Finally, we also generated a wild-type rhodopsin construct where all lysines were converted to arginine and found significantly reduced ubiquitylation. Our findings identify ubiquitinylation of lysine residues as an important posttranslational modification involved in P23H rhodopsin protein degradation."

Journal • Genetic Disorders • Inherited Retinal Dystrophy • Ocular Inflammation • Ophthalmology • Retinal Disorders • Retinitis Pigmentosa • Targeted Protein Degradation

Intravitreal Gene Therapy of Retinitis Pigmentosa (RP) Associated with Mutations in the CNGA1 Gene (CNGA1-RP) (ASGCT 2023) - "The therapy uses a novel recombinant adeno-associated virus (AAV) vector based on the engineered AAV2.NN capsid, carrying a genome that features a human rhodopsin promoter driving rod-specific expression of full-length human CNGA1...A GLP-safety study in rabbits applying single intravitreal injection followed by a 6-month post treatment observation period confirmed safety of AAV2.NN.hCNGA1. In summary, these results demonstrate the efficacy and safety of hCNGA1 gene supplementation therapy and support the translation of this approach toward future clinical application."

Gene therapy • Gene Therapies • Genetic Disorders • Inherited Retinal Dystrophy • Ocular Inflammation • Ophthalmology • Retinal Disorders • Retinitis Pigmentosa