Use of a Transgenic Human PNPLA3^I148M Knock-in Mouse for Translational Safety Evaluations of siRNA Therapeutics

The PNPLA3 single nucleotide polymorphism, rs738409, is the strongest known genetic risk factor for metabolic dysfunction-associated steatotic liver disease; thus, targeting the minor allele with a GalNAc-conjugated siRNA is an attractive strategy to treat patients carrying the genetic variant. To enable translational safety assessment of a GalNAc-conjugated siRNA that specifically targets the rs738409 sequence of PNPLA3, a transgenic human PNPLA3^I148M knock-in mouse (huPNPLA3^I148M) was utilized. This model showed no significant genotype-related phenotypic differences to wild-type mice in a phenotype characterization study when maintained on standard rodent chow. Additionally, a repeat-dose toxicology study using a GalNAc-conjugated siRNA specific for rs738409 resulted in comparable findings between genotypes (i.e., liver enzyme and histopathology changes), indicating the findings were due to the siRNA therapeutic and not a result of target knockdown in huPNPLA3^I148M mice. Overall, these data demonstrate the huPNPLA3^I148M mouse is suitable for repeat-dose toxicology studies, suggesting this approach could be applied to other siRNA programs lacking a pharmacologically relevant nonclinical species to support translational safety assessments during drug development.