Development of an artificial internal ribosome entry site to allow integration of modified nucleic acids into circular ribonucleic acid-based therapeutics

mRNA is a type of molecule naturally produced by the body that encodes instructions for the production of proteins, themselves responsible for most cellular functions. In the context of many diseases, the ability to administer a specific protein to cells is an interesting therapeutic avenue, but such an approach is problematic for many reasons such as immunogenicity, difficult transport and the hard-to-upscale production of pure proteins. The use of an mRNA molecule coding for a protein of interest has been considered as an alternative method for quite some time, but the inherent immunogenicity and low stability of mRNA has prevented its widespread adoption until recently, when the first mRNA therapeutics were commercialized as vaccines for COVID-19. The use of an N1-methylpseudouridine modification in the mRNA is what allowed for the technology to be viable as a therapeutic by reducing immunogenicity and increasing protein production. mRNA therapeutics have been shown to be clinically viable, but their use cases are still rather limited, mostly due to their low stability, which limits their use in scenarios such as protein replacement therapy. Circular RNAs are being investigated for their increased stability, which is due to their lack of any free extremities. Circular RNAs rely on Internal Ribosome Entry Sites (IRESs) to be functional, a different system than that of mRNA. The combination of RNA modifications like N1-methylpseudouridine with circular RNAs could theoretically yield a new, improved method of therapy for many diseases, but IRESs are incompatible with those modifications. The developement of an artificial IRES that can tolerate these modifications would allow incorporation into circular RNAs and thus, for an improved method of therapy to be developed.