Liver-Detargeted Aromatic Bioreducible mRNA Lipid Nanoparticles Confer Lymph Node Tropism and Robust Antigen-Specific Immunity

Lipid nanoparticles (LNPs) have been immensely successful in facilitating the delivery of nucleic acids to tissues of interest and continue to be optimized for mRNA delivery. These vehicles are particularly advantageous for vaccination due to their ease of production, highly tunable composition, and ability to induce robust immune responses without an adjuvant, as exemplified most recently by the clinical success of the Pfizer/BioNTech and Moderna COVID-19 vaccines. However, LNPs are known to exhibit off-target liver tropism. To address this limitation, we developed a library of aromatic bioreducible ionizable lipids that potently transfect secondary lymphoid tissues with liver detargeting capabilities compared with an industry standard ionizable lipid used in the COVID-19 vaccine. The library consists of three modular components: amine core structure, lipid tail length, and regiochemistry. These aromatic ionizable lipids employ benzene rings both as a scaffold for regiochemical differences and as a moiety to improve transfection. Bioreducible disulfide bonds in the lipids additionally serve to increase their biodegradability. When these aromatic ionizable lipids are formulated as LNPs, top-performing aromatic LNPs (aroLNPs) accumulate in and transfect lymph nodes while minimizing off-target liver tropism. Top-performing aroLNPs also induce strong antigen-specific immune responses, increased effector memory T cell generation, and decreased terminal effector T cell generation in mice when utilized in a preclinical SARS-CoV-2 vaccine study. Additionally, aroLNPs are strongly retained in the injection site and induce low levels of systemic inflammatory cytokines. Together, these results establish aroLNPs as a promising platform for vaccine delivery and potentially other immune-focused therapeutic applications.