Severe vision impairment or blindness undermine a key human sensory and personal experience, individual autonomy, leading to psychological distress, and consequently to social, and economic burdens to households and communities. In 2020, worldwide estimates counts more than 40 million people blind and 295 million people to have moderate and severe vision impairment. By 2050, the estimates forecast that more than 60 million people will be blind. From an economic standpoint, the most conservative model estimates the total cost of visual impairment in the EU to be 25.8 billion euros and 31.9 billion euros by 2050, with an overall enormous economic productivity loss. Despite this scenario, only one approved therapy for the treatment of genetic forms of blindness is on the market.
The ERC-POC 813223 “inSight” stemmed from the results of the ERC grant “Allelechocker” which supported a novel technology to switch off therapeutically the mutations of the RHODOPSIN gene (RHO). RHO mutations cause a blindness disorder called autosomal dominant retinitis pigmentosa (RHO-adRP), yet incurable. In the case of genetic disorders due to mutations causing a loss of the function of a gene (recessive genetic diseases) the gene must be replaced. The recent commercialization of “Luxturna” the first gene therapy product for the treatment of a form of genetic blindness, demonstrated the safety and efficacy of gene therapy replacement approach, and enabled the opening of a growing number of clinical trials with this gene therapy strategy. In the so called “dominant” genetic disorders such as RHO-adRP, typically, the mutations poison the cell and therefore, the mutations must be corrected or inactivated. Until recently, gene therapy approaches to correct or inactivate genes lagged behind gene replacement, representing a scientific challenge and a urgent unmet medical need. Gene correction or gene silencing via genomic editing technologies, recently opened a novel way to tackle experimentally these dominant disorders. CRISPR/CAS system is gaining momentum in this sector. In parallel, and alternatively, we first identified a then strengthened through the ERC-POC 813223 “inSight” a novel mode to silence genes to tackle dominant disorders.
Based on the discovery that a short sequence of DNA controls the expression of the RHO gene, and that when that specific DNA sequence is bound by a DNA binder protein, this protein inactivates RHO expression. The binding to this DNA RHO-specific sequence by the ZF6-DB protein, impedes the transcription of RHO into the messenger RNA (mRNA), thus blocking at the source the machinery which leads to the synthesis of the RHO protein. Consequently, this technology prevents the deleterious effects of the mutations to act. Notably, the ZF6-DB protein is designed based on a protein scaffold commonly present in humans, and it is small. In addition, being exclusively a DNA binder, ZF6-DB operates without hijacking or rerouting endogenous cellular systems. Furthermore, ZF6-DB works extremely efficiently at low doses. Finally, the ZF6-DB because of its dimension is easy to deliver with a unique AAV vector to the target organ, the retina.
We designed ZF6-DB to tackle any of the 150 mutations affecting RHO in a single gene therapy product. Aimed to this goal, we created a single AAV vector containing two gene therapy products, one, the ZF6-DB DNA binder, which switch off the RHO gene, and the other, the human RHO gene, to replace the silenced mutated RHO gene with a correct copy of it (“silencing and replacement” approach). The ZF6-DB enables the silencing of any of the 150 mutations that may cause RHO-adRP. Being enclosed in the same AAV vector system the two gene therapy products work together in the infected retinal photoreceptor cells of the retina, enabling the simultaneous silencing of the RHO gene and its replacement. To establish therapeutically relevant levels of expression of the “silencing and replacement” system, we varied the doses, and we evaluated the long-term consequences of AAV vector administration in the pre-clinical pig retina model, as planned in this InSight project. We determined that the ZF6-DB silences the RHO porcine gene at low levels of expression and that long-term (six months) expression of the gene therapy was well-tolerated, clinically, functionally (electrophysiological tests) and morphologically (histology). These results provided indications about the range of activity of the RHO silencing and replacement system. In parallel, Fondazione Telethon, FT, (the “additional beneficiary” of the project), performed the Business Development activities of inSight, including the Intellectual Property Rights (IPR) position and strategy, the competitive analysis, and the preliminary Start up valuation. The project has been proposed to companies and investors operating in the field to access specific competencies.
The current race to develop treatments for the medically challenging dominant genetic disorders, which we are witnessing, demonstrates the growing interest of scientists and investors on this topic, and supports the readiness of the market to these medicinal products. In this scenario, the discovery and validation of ZF6-DB as a therapeutic for a retinal condition, an ideal organ to test breakthrough therapies, may represent a game-changing innovation, which will impact the health and quality of life of patients affected by the disease, the households, and the communities in which they live and eventually the public health system. Finally, this novel treatment may represent a steppingstone for other retinal, non-retinal, and rare, non-rare disorders.
