Circular RNA vectors encapsulated in lipid nanoparticles for sustained protein replacement therapy in the retina

Circular RNAs (circRNAs) have recently emerged as promising vectors for sustained therapeutic protein production due to their enhanced stability from exonuclease degradation. Here, we engineered circRNAs expressing reporters and neurotrophic factors, and systematically compared their expression kinetics to conventional linear mRNAs. CircRNAs achieved 10-20 fold higher and more persistent protein expression in vitro over several weeks. We further demonstrated that circRNA-expressed nerve growth factor (NGF) provided lasting neuroprotection in a neuronal injury model compared to short-lived effects from NGF protein delivery. A major challenge for clinical translation of circRNAs is efficient intracellular delivery. We address this issue through lipid nanoparticle (LNP) encapsulation technology. LNPs successfully delivered circRNAs to retina after intravitreal or subretinal injection in mice, achieving localized and prolonged expression. As proof-of-concept, LNP-formulated circRNA expressing NGF promoted retinal ganglion cell survival in a mouse optic nerve crush injury model, demonstrating advantages over NGF protein injections. Collectively, this work establishes circRNA vectors as promising candidates for safe, sustained therapeutic protein production, and elucidates a delivery platform to overcome translational barriers. Realization of this technology may enable transformative treatments for chronic neurodegenerative protein deficiency diseases.