"Therapeutic mRNA is typically synthesized using in vitro transcription (IVT) with single-subunit polymerases (e.g., T7, T3, and SP6) using a DNA template to produce multiple copies of the coded mRNA. T7 RNA polymerase can incorporate chemically modified nucleotide triphosphates (NTP), particularly uridine modifications, which have been shown to maintain translational efficiency and alter the interactions between exogenous mRNA and TLR7, TLR8, and RIG-I (20)"

* [Impact of mRNA chemistry and manufacturing process on innate immune activation | Science Advances](https://advances.sciencemag.org/content/6/26/eaaz6893)