Multivalent ionizable lipid-polypeptides for tumor-confined mRNA transfection.

mRNA therapeutics is revolutionizing the treatment concepts toward many diseases including cancer. The potential of mRNA is, however, frequently limited by modest control over site of transfection. Here, we have explored a library of multivalent ionizable lipid-polypeptides (MILP) to achieve robust mRNA complexation and tumor-confined transfection. Leveraging the multivalent electrostatic, hydrophobic, and H-bond interactions, MILP efficiently packs both mRNA and plasmid DNA into sub-80 nm nanoparticles that are stable against lyophilization and long-term storage. The best MILP@mRNA complexes afford 8-fold more cellular uptake than SM-102 lipid nanoparticle formulation (SM-102 LNP), efficient endosomal disruption, and high transfection in different cells. Interestingly, MILP@mLuc displays exclusive tumor residence and distribution via multivalency-directed strong affinity and transcytosis, and affords specific protein expression in tumor cells and macrophages at tumor sites following intratumoral injection, in sharp contrast to the indiscriminate distribution and transfection in main organs of SM-102 LNP. Notably, MILP@mIL-12 with specific and efficient cytokine expression generates significant remodeling of tumor immunoenvironments and remarkable antitumor response in subcutaneous Lewis lung carcinoma and 4T1 tumor xenografts. MILP provides a unique strategy to site-specific transfection that may greatly broaden the applications of mRNA.