P23H RHO / Precision BioSci - LARVOL DELTA

RHO1-2 meganuclease gene editing targets human P23H rhodopsin-induced retinitis pigmentosa to rejuvenate rods and maintain cones. (PubMed, bioRxiv) - "They also suggest that meganuclease-based editors can be effective for other IRDs. Engineered meganuclease, RHO1-2 is a safe and promising therapeutic genome editing approach to cure human p.P23H RHO adRP."

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

Neuroprotection of photoreceptors by combined inhibition of both Fas and autophagy pathways in P23H mice. (PubMed, Cell Death Dis) - "Our previous data have shown that both the Fas (CD95) death receptor and hyperactivation of autophagy contribute to photoreceptor (PR) death in a mouse model of P23H-RHO adRP...Hydroxychloroquine (HCQ) was given in the drinking water at P21 to reduce autophagy flux...These results were recapitulated in HCQ-treated P23H mice receiving intravitreal injections of ONL1204. Our data suggest that in the mouse model of P23H adRD, inhibition of both the Fas pathway and autophagy pathways results in a greater protective effect, demonstrating the potential multipronged therapeutic approach to reduce PR death and improve retinal function in patients with P23H."

Journal • Preclinical • Genetic Disorders • Inflammation • Inherited Retinal Dystrophy • Ocular Inflammation • Ophthalmology • Retinal Disorders • Retinitis Pigmentosa • CDKN1A • FAS

P23H rhodopsin accumulation causes transient disruptions to synaptic protein levels in rod photoreceptors. (PubMed, Dis Model Mech) - "In this study we used super-resolution and electron microscopies, along with proteomics, to perform a subcellular analysis of Rho synaptic mislocalization in P23H-Rho-RFP mutant mice...In rd10 mutant rods, Rho mislocalized along the spherule plasma membrane, and there were synaptic protein abundance differences at age P20. Our findings demonstrate that some rod photoreceptor synaptic proteins are sensitive to Rho mislocalization."

Journal

Circadian clock disruption promotes retinal photoreceptor degeneration. (PubMed, FASEB J) - "We performed this study in the P23H rhodopsin-mutated mouse model (P23H Rho) that mimics one major cause of human autosomal dominant retinitis pigmentosa...In this data, we identified unique gene expression sets implicating neurogenesis, phototransduction cascade, and metabolism, associated with enhanced photoreceptor degeneration. Thus, our results establish a link between clock dysfunction and retinal degeneration and suggest underlying molecular mechanisms, together providing new concepts for understanding and managing blinding diseases."

Journal • Genetic Disorders • Inherited Retinal Dystrophy • Ocular Inflammation • Ophthalmology • Retinal Disorders • Retinitis Pigmentosa • ARNTL • BMAL1

Orally administered Deuterium-reinforced Docosahexaenoic Acid (D-DHA, BRX011) as a mutation-independent neuroprotective therapy for Autosomal Dominant Retinitis Pigmentosa (adRP) (ARVO 2025) - "We compared visual acuity (VA) and retinal function/structure in a humanized P23H RHO 'knock-in' adRP mouse model (hRHOP23H/+)2 fed D-DHA or H-DHA. Still, based on VA data, D-DHA may be a viable mutation-independent therapeutic candidate for adRP to maintain VA in RP patients.1Liu, Y. et al, 20222McCall M. et al, 2022 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."

Age-related Macular Degeneration • Dry Age-related Macular Degeneration • Inherited Retinal Dystrophy • Ocular Inflammation • Ophthalmology • Retinal Disorders • Retinitis Pigmentosa • CDKN1A

ER Aggregation Causes Synaptic Protein Imbalance in Retinitis Pigmentosa Mutant Photoreceptor Neurons. (PubMed, bioRxiv) - "This study examines the subcellular impact of Rho mislocalization on this presynaptic region caused by the P23H-Rho RP mutation and in other contexts. Mutant P23H-Rho-RFP fusion endoplasmic reticulum (ER) aggregation disrupted rod-specific synaptic protein levels, and combined with the detection of an endogenous presynaptic ER network in rods, this study supports a disease-relevant ER-based protein trafficking and turnover mechanism at rod synapses."

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

Oral Hydroxychloroquine (HCQ) for Retinitis Pigmentosa Caused by P23H- Rhodopsin (RHO) (clinicaltrials.gov) - P1/2 | N=8 | Terminated | Sponsor: University of Michigan | N=12 ➔ 8 | Trial completion date: Jan 2026 ➔ Aug 2024 | Recruiting ➔ Terminated | Trial primary completion date: Jan 2026 ➔ Aug 2024; Unable to recruit additional participants after multiple extensions to planned enrollment period.

Enrollment change • Trial completion date • Trial primary completion date • Trial termination • Genetic Disorders • Inherited Retinal Dystrophy • Ocular Inflammation • Ophthalmology • Retinal Disorders • Retinitis Pigmentosa

Development of TRIB3-Based Therapy as a Gene-Independent Approach to Treat Retinal Degenerative Disorders. (PubMed, Int J Mol Sci) - "The study employed rd10 and P23H RHO mice, with afatinib treatment conducted in p15 rd10 mice through daily intraperitoneal injections. The treated rd10 retinas also showed increased PDE6β and RHO staining, along with an elevation in total PDE activity in the retinas. Consequently, our study demonstrated the feasibility of a gene-independent strategy to target common signaling in degenerating retinas by employing a TRIB3-based therapeutic approach that delays retinal function and photoreceptor cell loss in two RD models."

Journal • Metabolic Disorders • Ophthalmology • EGFR • TRIB3

AAV-Mediated Delivery of a Novel CasX-Editor Molecule Achieves Allele-Specific and Potent Editing of P23H Rhodopsin in a Mouse Model of Retinitis Pigmentosa (ASGCT 2024) - "One strategy to address P23H.RHO-related adRP is the selective removal of the mutant Rho protein while preserving its wild-type (WT) counterpart, rescuing affected rod photoreceptors, and ultimately preventing vision loss...Using CasX for the first time in the mouse retina, we successfully reduce the production of mutant proteins, preserving vision in a model of retinal degeneration. This approach showcases the potential of CasX as a selective, potent, and engineerable tool in treating challenging genetic eye disorders."

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

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

A cell-based assay to identify small molecules that enhance the traffic of ABCA4 misfolding variants. (ARVO 2024) - "Rhodopsin (RHO) served as positive control, while ER-retained P23H-RHO as negative control... The proximity complementation assay can identify compounds that rescue missense variant ABCA4 traffic. Retinal organoids can be used to screen the effect of potential therapies facilitating the discovery of breakthrough agents for rescuing ABCA4 protein defects and mitigating ABCA4-related retinopathy."

Ophthalmology • Retinal Disorders

Identification of factors involved in rod regeneration and integration in a Zebrafish model of Retinitis Pigmentosa. (ARVO 2024) - "We have previously generated and characterized a Zf model (P23H rho) with continuous degeneration and regeneration of rods... DEGs found in RPCs and new rods of the P23H Zf dataset appear to play important roles in the regeneration and integration of new rods in the retina. Prdm1a plays an important role in the differentiation of RPCs into rods. Knockdown of dscamb, ncam1b, and auts2b increased BPC axon length while knockdown of ncam1b alone increased the number of co-localizations found between rods and BPC dendrites."

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

Oral Hydroxychloroquine (HCQ) for Retinitis Pigmentosa Caused by P23H- Rhodopsin (RHO) (clinicaltrials.gov) - P1/2 | N=12 | Recruiting | Sponsor: University of Michigan | Trial completion date: Oct 2025 ➔ Jan 2026 | Trial primary completion date: Oct 2025 ➔ Jan 2026

Trial completion date • Trial primary completion date • Genetic Disorders • Inherited Retinal Dystrophy • Ocular Inflammation • Ophthalmology • Retinal Disorders • Retinitis Pigmentosa

Comparison of Visual Acuity with Decline of Retinal Structure and Function in a Murine Model of P23H Retinitis Pigmentosa – Is There a Role of Plasticity? (ARVO 2023) - "We compared changes in visual acuity (VA) with retinal structure/function from early to late-stage disease in a murine P23H Rho ‘knock-in’ mouse model (Rho P23H/+ )...1 Sakami S, et al., 2011 J Biol Chem: 286(12) 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."

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

Analysis of P23H rhodopsin mislocalization in rod photoreceptor synapses during retinitis pigmentosa progression (ARVO 2023) - "Methods We used a combination of structured illumination microscopy (SIM), transmission electron microscopy (TEM), and quantitative confocal microscopy to characterize the impact of Rho mislocalization on synaptic morphology and protein expression in knockin P23H-hRho-RFP mice that contain the human P23H RHO gene fused to a red fluorescent protein...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."

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

Binocular benefit following monocular subretinal AAV injection in a mouse model of autosomal dominant retinitis pigmentosa (adRP). (PubMed, Vision Res) - "We, therefore, injected mice transgenic for human P23H RHO with this vector unilaterally at postnatal day 30...In addition, protective neurotrophic factors bFGF and GDNF were elevated in both eyes of treated mice. Our finding suggests that using this or similar RNA replacement vectors in human gene therapy may provide clinical benefit to both eyes of patients with adRP."

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

Oral Hydroxychloroquine (HCQ) for Retinitis Pigmentosa Caused by P23H- Rhodopsin (RHO) (clinicaltrials.gov) - P1/2 | N=12 | Recruiting | Sponsor: University of Michigan | Trial completion date: Oct 2023 ➔ Oct 2025 | Trial primary completion date: Oct 2023 ➔ Oct 2025

Trial completion date • Trial primary completion date • Genetic Disorders • Inherited Retinal Dystrophy • Ocular Inflammation • Ophthalmology • Retinal Disorders • Retinitis Pigmentosa

Galanin receptor 3 - a new pharmacological target in retina degeneration. (PubMed, Pharmacol Res) - "Furthermore, in P23H Rho knock-in mice, a model of retinitis pigmentosa (RP), both pharmacological inhibition and genetic ablation of GALR3 prolonged the survival of photoreceptors. These results indicate that GALR3 signaling contributes to acute light-induced and chronic RP-linked retinopathies. Together, this work provides the pharmacological knowledge base to evaluate GALR3 as a potential target for developing novel therapies to combat retinal degeneration."

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

GADD34 Ablation Exacerbates Retinal Degeneration in P23H RHO Mice. (PubMed, Int J Mol Sci) - "Additionally, GADD34 controls cytokine expression and STAT3 activation. Perhaps these molecular events are particularly important in controlling the pace of retinal degeneration."

Journal • Preclinical • Ophthalmology • EIF2A • EIF2S1 • IL6 • PPP1R15A • STAT3 • TNFA • TNS1

Mass Spectrometry Identification of Wild-type and P23H Rhodopsin Protein Interactome (ARVO 2022) - "Purpose: P23H rho is a common genetic cause of retinitis pigmentosa and encodes for misfolded P23H rhodopsin protein... Proteomic analysis reveals numerous differences between P23H and WT rhodopsin protein interactome. The P23H rhodopsin interactome is enriched in translational and post-translational quality control processes. The P23H rhodopsin interactome differs throughout all regions of the rod photoreceptor cell."

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

Investigation of ABCA4 missense variant plasma membrane trafficking in cell models. (ARVO 2022) - "The plasma membrane specificity of the quantitative assay and the ability to detect pharmacological rescue of protein folding was confirmed using WT rhodopsin (RHO) and the misfolding P23H-RHO variant... Reduced growth temperature can enhance the plasma membrane traffic of WT and missense variants of ABCA4 in cultured cells, suggesting that some of these variants are temperature sensitive misfolding variants that might be amenable to pharmacological rescue. The assay we developed is able to quickly and robustly detect plasma membrane localization, which could be used as a surrogate marker for correct folding and trafficking, and has potential use for high-throughput screening of small molecules able to restore ABCA4 folding."

Ophthalmology

NANOBODY rescues adRP phenotype in a P23H adRP cell model, suggesting therapeutic potential (ARVO 2022) - "After confirming their binding affinity to native bovine ROS by gel shift assay, selected Nbs were expressed intracellularly in bovine wild type (WT)-RHO cells, or P23H-RHO HEK293 cells... Intracellular expression of Nbs rescues the mutant RHO phenotype in an in vitro HEK293 adRP model, suggesting therapeutic potential of the nanobody technology. Since there are few treatment options for RHO-adRP, NANOBODY technology might offer a new treatment option regardless of a patient’s genetic background."

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

GADD34 does not affect the translational rate in P23H RHO mouse retina (ARVO 2022) - "Our results indicate that GADD34 deficiency does not affect the rate of protein synthesis during chronic ER stress, suggesting that p-eIF2α is not the major point of translational control in progressive RD. GADD34 may control the inflammatory response of P23H Rho retinas, and its deficiency may alter pro- and anti-inflammatory cytokine ratios, thus resulting in compromised photoreceptor homeostasis."

Preclinical • Inherited Retinal Dystrophy • Ocular Inflammation • Ophthalmology • Retinal Disorders • Retinitis Pigmentosa • EIF2A • EIF2S1 • IL6 • PPP1R15A • TNFA • TNS1

Subcellular localization of mutant P23H rhodopsin in an RFP fusion knockin mouse model of retinitis pigmentosa. (PubMed, Dis Model Mech) - "mRNA levels for both the mutant human rhodopsin allele and the WT mouse rhodopsin levels were reduced, but protein levels revealed selective degradation of the mutant protein. The results suggest the mutant rods undergo an adaptative process that prolongs survival despite unfolded protein accumulation in the ER. The P23H-Rho-RFP mouse may represent a useful tool for the future study of the pathology and treatment of P23H-Rho and adRP."

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

Flavonoids improve the stability and function of P23H rhodopsin slowing down the progression of retinitis pigmentosa in mice. (PubMed, J Neurosci Res) - "Thus, we hypothesized that flavonoids by binding to P23H Rho and enhancing its conformational stability could mitigate detrimental effects of this mutation on retinal health...In addition, treatment with quercetin resulted in downregulation of the UPR signaling and oxidative stress-related markers. This study unravels the pharmacological potential of quercetin to slow down the progression of photoreceptor death in Rho-related RP and highlights its prospective as a lead compound to develop a novel therapeutic remedy to counter RP pathology."

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