Lipid nanoparticle toxicity has long been an industry concern.

In a profile of Moderna back in 2016, Katalin Karikó (instrumental in the development of mRNA vaccines) mentioned this issue:

“I would say that mRNA is better suited for diseases where treatment for short duration is sufficiently curative, so the toxicities caused by delivery materials are less likely to occur” [1]

[1] https://www.statnews.com/2016/09/13/moderna-therapeutics-bio...