DB-LNPs were used to deliver Cas9 mRNA/sgRNA for editing the TTR gene and mRNA encoding human fibroblast growth factor 21 (FGF21) to the liver as a strategy to treat the genetic disease transthyretin amyloidosis, and obesity and fatty liver, respectively. The gene discussed is FGF21; the disease is obesity due to melanocortin 4 receptor deficiency.