Nonclinical safety evaluation strategies for mRNA/LNPs platform agents: Evidence from comprehensive animal toxicity studies.

Antigen-encoded messenger RNA (mRNA) formulated with lipid nanoparticles (LNPs) represent a rapidly expanding platform technology, extending beyond prophylactic infectious disease vaccines into therapeutic applications. Despite their increasing clinical use, harmonized and modality-specific guidance for nonclinical safety evaluation of mRNA/LNP platform agents remains limited, creating regulatory uncertainty during investigational new drug (IND)-enabling development. In this study, we systematically evaluated key variables influencing nonclinical safety profiles of mRNA/LNP agents from a regulatory toxicology perspective. Using comprehensive animal (mice and cynomolgus macaques) toxicity studies, we examined the impact of dose level (25∼100 μg/head), LNP composition, mRNA platform type (modified, unmodified, self-amplifying, and circular mRNA), antigen encoding, and animal species selection on toxicological outcomes. Dose-dependent toxicity profiling in mice revealed parameter-specific responses across hematological, biochemical, and organ weight parameters, underscoring the regulatory relevance of rational dose selection. Comparative analyses demonstrated that LNP composition alone can drive distinct toxicity phenotypes, while mRNA/LNPs platform further modulated specific toxicological parameters such as AST, reticulocyte and cardiac troponin I levels. Importantly, different mRNA platforms resulted in distinct toxicological patterns, particularly with respect to platelet counts and cardiac troponin I levels. Repeated-dose studies in non-human primates identified reversible toxicological changes, while revealing species-specific minor differences in selected blood chemistry and organ weight parameters not observed in rodents. Collectively, these findings highlight that nonclinical safety profiles of mRNA/LNP agents are shaped by multiple interdependent platform variables. This study provides regulatory-relevant experimental evidence to inform evidence-based nonclinical study design and interpretation, supporting development of mRNA vaccines and therapeutics.