Redefining Retinal Gene Delivery: Expanding the Possibilities Beyond Conventional Vectors

Gene therapy has transformed the outlook for inherited retinal disorders, offering hope to patients with conditions that were once considered untreatable. Yet despite remarkable scientific progress, many retinal diseases remain beyond the reach of current therapies. The challenge often lies not in identifying therapeutic targets, but in safely and effectively delivering genetic material to the cells that need it most.

Today, adeno-associated viral vectors (AAVs) dominate the ophthalmic gene therapy landscape. Their success has paved the way for groundbreaking treatments and validated the potential of genetic medicine. However, these vectors are not without limitations. Restricted packaging capacity limits the size of genetic payloads they can carry, while concerns around immunogenicity and patient compliance continue to shape the boundaries of their use.

Alternative delivery systems, including synthetic lipid nanoparticles, have emerged to address some of these shortcomings. Yet in the delicate environment of the eye, inflammatory responses remain an important consideration. As researchers seek to expand treatment possibilities for inherited retinal disorders, the field faces a pressing question: can we develop delivery technologies that combine safety, efficiency and versatility without compromising therapeutic potential?

The answer may lie in learning from biology itself.

Extracellular vesicles (EVs), naturally secreted by cells to facilitate intercellular communication, have attracted growing interest as potential therapeutic carriers. Their intrinsic biocompatibility offers an opportunity to rethink how messenger RNAs are transported and delivered. However, practical barriers have slowed their translation into gene therapy applications. Efficiently loading exogenous RNA, particularly large messenger RNAs into natural EVs has remained a significant bottleneck. Existing approaches often rely on manipulating producer cells during secretion, resulting in limited reproducibility, increased complexity and inconsistent loading efficiency.

At EVis Bioscience AG, an ETH Zürich spin-off, we are exploring whether hybrid extracellular vesicles derived from patient material can address these longstanding challenges. Our semi-autologous platform utilizes patient-derived hybrid extracellular vesicles (p-hEVs) as non-viral carriers designed to deliver messenger RNAs to retinal cells.

Preclinical investigations have yielded encouraging findings. The technology has demonstrated the ability to deliver messenger RNAs larger than 4.7 kilobases and selectively transduce retinal pigment epithelium and Müller glia cells in human retinal models and following intravitreal administration in healthy mouse models. This result suggests potential therapeutic opportunities for diseases that do not yet have effective therapies, e.g., X-linked retinoschisis. In parallel, our platform has achieved messenger RNA loading efficiencies exceeding 90 percent without requiring additional purification steps, suggesting a practical and scalable approach to formulating RNA-loaded extracellular vesicles.

Importantly, the implications extend beyond ophthalmology. A highly efficient strategy for loading RNAs into natural EVs could unlock broader opportunities for extracellular vesicle-based therapeutics across a wide range of medical applications. By overcoming one of the field's most persistent technical barriers, researchers may gain access to a versatile platform capable of supporting future gene therapy innovations.

Ongoing preclinical programs in healthy and diseased human retinal models, alongside animal studies, are expected to further establish proof of concept for this approach. The significance of this work has been recognized through support from Innosuisse, the Swiss Innovation Agency, which awarded funding to advance these investigations. More recently, EVis Bioscience completed a successful pre-seed financing round through Capital Cell, further accelerating development efforts.

Ultimately, innovation in retinal gene therapy will depend not only on discovering new therapeutic payloads but also on advancing the delivery systems that make those therapies possible. Expanding the range of diseases that can be addressed safely and effectively requires moving beyond the constraints of existing technologies and embracing novel approaches rooted in biological design.

For patients living with inherited retinal disorders that currently lack treatment options, these advances represent more than scientific progress. They offer the possibility of preserving vision and redefining what gene therapy can achieve.