Serum factors create species-specific barriers to hepatic gene transfer by lipid nanoparticles in liver-humanized mice

Lipid nanoparticles (LNPs) can efficiently deliver nucleic acid therapeutics to a range of tissues, particularly hepatocytes to treat diseases of the liver. We initially investigated whether three LNPs with different ionizable lipids, previously validated in non-human primates (NHPs), could deliver functional <i>GFP</i> mRNA to human hepatocytes in chimeric NSG-PiZ and FRG mice. After intravenous delivery, GFP expression was observed throughout the livers but was restricted to mouse hepatocytes because the payload mRNA was not internalized by human hepatocytes. LNP transfection was also restricted to mouse hepatocytes in NSG-PiZ mice administered a different LNP containing the ionizable lipid SM-102. <i>In vitro</i>, primary human hepatocytes (PHHs) were transfected by LNPs containing lipids SM-102, LP01, or ALC0315 in the presence of normal mouse serum, but not chimeric NSG-PiZ serum. SM-102 LNP transfection of PHH was also inhibited by naive untransplanted NSG-PiZ serum. However, serum from NSG mice supported PHH transfection by SM-102 LNP. These results suggest that inhibitory factors in NSG-PiZ mouse serum are responsible for the lack of human hepatocyte transduction in chimeric mice. Finally, we found that LNPs displaying trivalent N-acetylgalactosamine (TriGalNAc), which targets them to the asialoglycoprotein receptor, can overcome species restriction, transfecting both mouse and human hepatocytes in chimeric NSG-PiZ mice.