RNA enhances for durable base-modified mRNA therapeutics

mRNA is a powerful gene transfer platform, but its limited stability remains a major challenge. While alternative RNA formats offer greater durability, they often suffer from low translation, modification incompatibility, and complex manufacturing. To overcome these limitations, we screened 196,277 viral segments and identified eleven RNA elements that enhance both mRNA stability and translation. Mechanistically, these enhancers recruit TENT4 to extend poly(A) tail, preventing deadenylation. Five of them are compatible with N1-methylpseudouridine, a modification that improves mRNA efficacy and reduces immunogenicity. Among them, an element named A7 demonstrated robust performance across cell types, delivery methods, and coding sequences. Remarkably, A7-containing linear mRNA exhibited stability comparable to circular RNA while achieving substantially higher translation efficiency. In mouse liver, A7-containing linear mRNA enabled several hundred-fold higher protein levels than circular RNA, with sustained expression lasting over two weeks. These RNA enhancers establish a potent and durable linear mRNA platform with low immunogenicity and simple design and manufacturing.