Abstract Aim Lipid nanoparticle (LNP)-encapsulated mRNAs (mRNA-LNPs) are being explored for various prophylactic and therapeutic applications. However, the relationship between the pharmacokinetics (PK) of lipid, mRNA, and expressed protein across tissues remains poorly understood. This study aimed to perform a biodistribution study to quantitatively assess this relationship. Methods Spike protein encoding mRNA was encapsulated in LNPs formulated with ALC-0315. mRNA-LNP was administered intravenously in mice. Biodistribution of ALC-0315, mRNA and expressed spike protein was determined in plasma and several tissues using LC–MS/MS, RT-qPCR and ELISA, respectively. Anti-spike protein IgM and IgG titers were also quantified using ELISA. Results ALC-0315 lipid was cleared rapidly from plasma but persists in tissue for several weeks post dosing, with highest uptake seen in liver and spleen, and the lowest in muscle and brain. Unlike lipid, the highest mRNA exposure was observed in spleen followed by liver. Spike protein expression was detected within minutes of dosing and peaked at 6 h. Maximum protein expression was observed in liver, followed by spleen, heart, kidney and lung. A robust humoral immune response was triggered against spike protein, with IgM titers detected as early as 24 h and IgG titers detected on day 7. Conclusion The PK of lipid, mRNA, and protein components differ significantly. The plasma PK for all three analytes differed significantly from tissue PK. Synthetic ionizable lipid ALC-0315 persisted in tissues for several weeks post dosing. After intravenous dosing, mRNA-LNP was found to be rapidly taken up by the tissues, and protein expression detected within one hour in all tissues.
Kumar et al. (Thu,) studied this question.