How the initial discovery of modified RNA enabled evasion of innate immune responses and facilitated the development of RNA therapeutics

Besides being the physical link between DNA and proteins, RNAs play several other key roles, including RNA catalysis and gene regulation. Recent advances in the design of lipid nanoparticles have facilitated the development of RNA-based therapeutics. However, chemically and in vitro transcribed RNAs can activate innate immunity, leading to the production of proinflammatory cytokines and interferons, a response similar to the one induced by viral infections. Since these responses are undesirable for certain therapeutic applications, it is important to develop ways to block the sensing of exogenous RNAs by immune cells, such as monocytes, macrophages and dendritic cells. Fortunately, RNA sensing can be blocked by chemical modifications of certain nucleotides, particularly uridine, a finding that has facilitated the development of RNA-based therapeutics such as small interfering RNAs and mRNA vaccines. Here, I provide a backstory on how improved understanding of RNA sensing by innate immunity can be applied to develop more effective RNA therapeutics.