Cost-effective yet high-performance ionizable lipids for mRNA-lipid nanoparticle vaccines.

Abstract

Ionizable lipids (ILs) are critical components in mRNA vaccines, which have been instrumental in the global response to SARS-CoV-2. However, current commercialized ILs in mRNA vaccines are typically synthesized through multiple-step organic reactions, complicating quality control and driving up production costs. To address this, we have developed novel ILs by a one-pot Ugi four-component reaction (Ugi-4CR), significantly simplifying synthesis while maintaining high yields and reducing costs. Here, from a library of 161 ILs, we chose six ILs with high expressing luciferase and investigated their performance in delivering the mRNA vaccine of SARS-CoV-2. These ILs feature distinct ionizable heads, N,N-dimethylethyl (R1), N,N-dimethylpropyl (R2), and N,N-diethylpropyl (R3), paired with hydrophobic tails of varying unsaturation, cis-9-octadecenoic (U1) and (9Z,12Z)-9,12-octadecadienoic (U2), respectively. In murine models, R2-and R3-based mSpike-LNPs induce higher antibody titers and stronger cellular immune responses compared to the R1-based counterparts, suggesting their superior mRNA delivery and expression efficiency. Notably, R2U2- and R3U2-based mSpike-LNPs further enhance IFN-γ⁺ splenocyte responses and activation of TNF-α⁺CD4⁺/CD8⁺ T cells, coupled with improved dendritic cell activation and retention in lymph nodes. We confirm that the R2U2-based LNPs on different mRNA antigens exhibit immune responses and safety profiles comparable to the commercial ALC-0315-based LNPs. Moreover, intranasal and intratracheal administration of R2U2-based mSpike-LNPs enhances mucosal immunity, as evidenced by elevated sIgA levels in mice. Further evaluation in cynomolgus macaques proves the efficacy of this LNP system, highlighting its potential for developing cost-effective mRNA vaccines.