Background
For a successful mRNA cancer vaccine, delivery of antigen-encoding mRNAs to professional APCs can be achieved by employing delivery vehicles that target lymphoid organ enriched in DCs. After cellular uptake, efficient release of mRNA from the endosome to cytosol is an essential step for antigen protein expression and presentation to T cells. Proper antigen presentation by APCs leads to tumor specific cytotoxic T cell responses. NanoReady was developed to selectively deliver mRNA to splenic DCs and enable effective endosomal release of mRNA resulting in high antigen expression and anti-cancer immune responses that halt tumor growth and enhance survival in murine tumor models.
Methods
The physicochemical properties of NanoReady-mRNA nanoparticles were characterized by DLS, cryo-EM and NTA techniques. Tissue and cell biodistribution of the NanoReady-FLuc mRNA were evaluated in mice and NHPs after intravenous administration by BLI using IVIS Spectrum, flow cytometry and immunofluorescence staining. Cellular endosomal escape was analyzed by confocal microscopy. Antigen specific T cell immune responses were evaluated in mice and NHP by ELISPOT assays. Anti-tumor efficacy was evaluated in C57BL6-B16F10 tumor model.
Results
NanoReady is a lipid-polymeric nanoparticle, and when mixed with mRNA it forms a multi-lamellar structure with large mRNA-loading capacity. NanoReady selectively delivers mRNA to spleen in mice and NHPs with the majority being delivered to the DCs. NanoReady leads to high protein expression of mRNA in DCs, which is associated with the highly efficient endosomal mRNA release. NanoReady-mTRP2 mRNA administered C57BL6-B16F10 tumor model showed improved efficacy of tumor growth inhibition and survival improvement, correlating with a strong antigen specific T cell immune response. Similarly, potent T cell immune response was detected in NHPs when administered with NanoReady-rhTERT mRNA. Furthermore, no adverse reactions or changes in CBC, cytokines and tissues were observed during repeated administrations in both mice and monkeys.
Conclusions
Numerous efforts in developing an antigen delivery platform that enables breaking tolerance of self-immune responses for cancer vaccine approaches have been made with limited success. NanoReady efficiently delivers antigen mRNA to splenic DCs and promotes endosome release resulting in high antigen protein expression. Importantly, NanoReady induces potent CD8 T cell responses to tumor associated antigens including highly immune-tolerant self-antigens. NanoReady can be preassembled into nanoparticles in the absence of mRNA and can be later mixed with a diverse size range of mRNA payloads for personalized cancer vaccine applications. Taken together, NanoReady as a cancer vaccine delivery platform is expected to open up new personalized treatment options for cancer patients.