See 2017

https://www.statnews.com/2017/01/10/moderna-trouble-mrna/

mRNA is a tricky technology. Several major pharmaceutical companies have tried and abandoned the idea, struggling to get mRNA into cells without triggering nasty side effects.

But the Crigler-Najjar treatment has been indefinitely delayed, an Alexion spokeswoman told STAT. It never proved safe enough to test in humans, according to several former Moderna employees and collaborators who worked closely on the project. Unable to press forward with that technology, Moderna has had to focus instead on developing a handful of vaccines, turning to a less lucrative field that might not justify the company’s nearly $5 billion valuation.