Engineered circRNA platform with BBV CITE delivers GLP-1 peptides, matching semaglutide efficacy in obese mice

Traditional linear mRNA therapeutics face limitations due to their inherent instability and immunogenicity, often requiring extensive modifications. While circular RNA (circRNA) offers enhanced stability and protein expression, integrating nucleoside modifications to further improve translational efficiency and reduce immunogenicity has been technically challenging. This gap has hindered the development of circRNA as a versatile platform for delivering therapeutic proteins and peptides, particularly for conditions like type 2 diabetes and autoimmune diseases, where sustained, low-immunogenicity expression is critical.

Researchers engineered a novel circRNA platform by identifying a cap-independent translation enhancer (CITE) from black beetle virus, termed BBV, capable of driving translation of nucleoside-modified RNA and rolling circle translation (RCT). They developed a 'scarless' in vitro transcription (IVT) system to produce these circRNAs. The platform was tested in several murine models: a tumor model (comparing circRNA vaccine to m1ψ-mRNA vaccine), obese mice (using circRNA encoding glucagon-like peptide-1 peptides), and an experimental autoimmune encephalomyelitis (EAE) model (using circRNA encoding myelin oligodendrocyte glycoprotein (MOG35-55) peptides). Efficacy was assessed via tumor growth, cytokine expression (ELISA), blood glucose levels, liver damage markers, and disease progression.

The engineered circRNA vaccine significantly outperformed m1ψ-mRNA vaccine in inhibiting tumor growth in mice. Nucleoside modification of the circRNA led to reduced expression of pro-inflammatory cytokines, indicating lower immunogenicity. Critically, nucleoside-modified circRNA encoding GLP-1 peptides demonstrated remarkable metabolic benefits: > It reduced blood glucose levels with efficacy comparable to that of commercial semaglutide in obese mice. Furthermore, this GLP-1-encoding circRNA also ameliorated liver damage in the obese mouse model. In the EAE murine model, nucleoside-modified circRNA encoding MOG35-55 peptides successfully induced immune tolerance and alleviated disease progression, highlighting its potential in autoimmune contexts. These findings collectively establish a robust nucleoside-modified circRNA platform for efficient, low-immunogenicity protein/peptide translation.