The idea that mRNA could be used for therapeutic purposes was first realized in 1989 by researchers,
R. W. Malone, P. L. Felgner, and I. M. Verma, at Vical, a Californian biotechnology start-up.[3][15] Researchers working with the Salk Institute that year published an article showing that nanoparticles could transfect mRNA into cells.[16][15] In 1990, Jon Wolff at the University of Wisconsin collaborated with researchers, Jon A.Wolff, Robert W. Malone, Phillip Williams, Wang Chong, Gyula Acsadi, Agnes Jani Philip L. Felgner, of Vical and reported positive results where "naked" (or unprotected) mRNA was injected into the muscle of mice.[3][17] These studies were the first evidence that in vitro transcribed (IVT) mRNA could deliver the genetic information to produce proteins within living cell tissue.[3]
https://en.wikipedia.org/wiki/RNA_vaccine
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