Chemistry-Based mRNA Design Enhancing Translation toward Therapeutics

ABSTRACT

Messenger RNA (mRNA) therapeutics have traditionally been produced by enzymatic transcription, yet chemistry offers powerful levers to optimise translation, stability, and safety. We first developed PureCap, a hydrophobic-tagged cap analogue that enables single-step RP-HPLC purification of fully capped mRNA, yielding transcripts of unrivalled purity (Nat. Commun., 2023). Building on this, we achieved the total chemical synthesis of mRNA through efficient 5′-phosphorylated RNA assembly and one-pot chemical capping, overcoming the length‑constraint typical of solid‑phase approaches (ACS Chem. Biol., 2022).

To further boost protein output, we recently introduced an internal cap-initiated translation (ICIT) strategy for circular mRNA. By covalently grafting an m⁷G cap onto a branched RNA element (cap‑circ mRNA) or tethering an m⁷G‑modified oligonucleotide (cORN), translation was enhanced up to 10³‑fold compared with uncapped controls. When combined with N¹‑methylpseudouridine, ICIT constructs drove robust and durable expression in vitro and in vivo while minimising innate immune activation (Nat. Biotechnol., 2025).

These chemistry‑based innovations—precise capping, total chemical synthesis, and ICIT—collectively constitute a versatile platform for next‑generation mRNA vaccines, cancer immunotherapy, anin‑replacement therapies.

References:

1.        Kawaguchi, D., Kodama, A., Abe, N., Takebuchi, K., Hashiya, F., Tomoike, F., Nakamoto, K., Kimura, Y., Shimizu, Y., & Abe, H. Phosphorothioate modification of mRNA accelerates the rate of translation initiation to provide more efficient protein synthesis. Angewandte Chemie International Edition 2020, 59(40), 17403-17407

2.        Abe, N., Imaeda, A., Inagaki, M., Li, Z., Kawaguchi, D., Onda, K., Nakashima, Y., Uchida, S., Hashiya, F., Kimura, Y., & Abe, H. Complete Chemical Synthesis of Minimal Messenger RNA by Efficient Chemical Capping Reaction. ACS Chem. Biol. 2022, 17(6), 1308-1314.

3.        Inagaki, M., Abe, N., Li, Z., Nakashima, Y., Acharyya, S., Ogawa, K., Kawaguchi, D., Hiraoka, H., Banno, A., Meng, Z., Tada, M., Ishida, T., Lyu, P., Kokubo, K., Murase, H., Hashiya, F., Kimura, Y., Uchida, S., & Abe, H. Cap analogs with a hydrophobic photocleavable tag enable facile purification of fully capped mRNA with various cap structures.  Nat Commun. 2023 14(1), 2657.

4.        Fukuchi, K.; Nakashima, Y.; Abe, N.; Kimura, S.; Hashiya, F.; Shichino, Y.; Liu, Y.; Ogisu, R.; Sugiyama, S.; Kawaguchi, D.; Inagaki, M.; Meng, Z.; Kajihara, S.; Tada, M.; Uchida, S.; Li, T.-T.; Maity, R.; Kawasaki, T.; Kimura, Y.; Iwasaki, S.; Abe, H. Internal Cap-Initiated Translation for Efficient Protein Production from Circular mRNA. Nat. Biotechnol. 2025, 1–13. https://doi.org/10.1038/s41587-025-02561-8.

*This lecture will also be available online (https://kaist.zoom.us/j/88244379581) .