Summary
Achieving precise delivery of messenger RNA(mRNA) to specific organs remains a significant challenge for the practical application of mRNA technology in vivo. In the context of mRNA vaccines, targeting delivery to the lymph node(LN) holds the promise of reducing side effects while enhancing the immune response. In this study, we investigated an endogenous LN-targeting lipid nanoparticle(LNP) devoid of any active targeting ligand modifications, with the aim of developing an mRNA-based cancer vaccine.
The LNP, named 113-O12B, exhibited heightened and selective expression within the LN when compared to LNPs formulated with ALC-0315, a synthetic lipid found in the COVID-19 vaccine Comirnaty. This targeted mRNA delivery to the LN notably amplified the CD8+ T cell response against the encoded full-length ovalbumin(OVA) model antigen. Consequently, the protective and therapeutic effects of the OVa-encoded mRNA vaccine against OVA-antigen-bearing B16F10 melanoma were significantly enhanced. Furthermore, when encapsulated with TRP-2 peptide (TRP2180-188)-encoding mRNA, 113-O12B demonstrated remarkable tumor inhibition. Notably, in conjunction with anti-programmed death-1(PD-1) therapy, a complete response of 40 % was observed in the standard B16F10 tumor model, showcasing the broad applicability of 113-O12B for protein as well as peptide antigens
Amid the severe acute respiratory syndrome coronavirus 2 (SARS-COV-2) pandemic, messenger RNA (mRNA) vaccines have attained notable success, garnering increased attention within the field. In comparison to other vaccine types, mRNA vaccines offer several advantages, encompassing rapid production, safety, and a robust immune response.
Notably, mRNA vaccines facilitate the transient expression of tumor antigens, mitigating potential mutations associated with DNA vaccines. Moreover, the versatility of mRNA cancer vaccines enables encoding a diverse array of antigens, spanning full proteins and peptides, thereby demonstrating flexibility in consolidating essential tumor antigens.
Furthermore, relative to conventional inactivated pathogen or protein-based vaccines, mRNA cancer vaccines elicit more potent humoral and cellular responses, leading to enhanced therapeutic outcomes. Buoyed by the superiority of mRNA vaccines, the application of mRNA technology to cancer treatment has been swiftly expanding. Presently, over 20 mRNA cancer vaccines are undergoing clinical trials.
In the realm of mRNA vaccines, two pivotal factors come to the forefront: the mRNA itself and the delivery system. Substantial strides have been taken in optimizing both mRNA production and diverse delivery systems. One of the primary challenges posed by mRNA is its heightened immunogenicity, a concern that has been effectively addressed and mitigated through nucleic acid modifications. The incorporation of a cap structure and a polyA tail serves to enhance mRNA stability and facilitate transfection. Additionally, the evolution of innovative mRNA delivery systems, particularly lipid nanoparticles (LNPs), has markedly improved mRNA stability and transfection efficiency within human subjects.
LNPs, the most prevalent RNA delivery vehicle, can be categorized into three generations based on their attributes. The first generation, comprising non-degradable compounds like 1,2-dioleoyl-3-dimethylaminopropane and 1,2-dilinoleoyloxy-N,N-dimethyl-3-aminopropane, exhibits moderate transfection capabilities but notable in vivo toxicity.
The second generation, exemplified by 4-(dimethylamino)-butanoic acid and (10Z,13Z)-1-(9Z,12Z)-9,12-octadecadien-1-yl-10,13-nonadecadien-1-yl ester (DLin-MC3-DMA) with biodegradable ester linkers, efficiently delivers small RNAs like small interfering RNA (siRNA) to the liver, achieving substantial and sustained knockdown of targeted serum proteins.
The third generation including ALC-0315, and SM-102, exhibit high transfection efficiency for long-chain mRNA in vivo and were utilized in the production of COVID-19 mRNA vaccines. However, despite the significant progress made in LNP development for mRNA delivery, a substantial portion of reported LNPs administered intravenously (IV) or intramuscularly (IM) have demonstrated strong mRNA expression primarily within the liver. Pfizer's pharmacokinetics data submitted to the European Medicines Agency (EMA) concerning the COVID-19 mRNA vaccine (BNT162b2) administered via IM injection indicated predominant distribution in the liver and the injection site, leading to reversible hepatic damage in animals. Moreover, the BNT162b2 mRNA was found to undergo intracellular reverse transcription into DNA within as little as 6 hours in a human liver cell line (Huh7), potentially posing a significant health risk. Notably, vaccination with BNT162b2 was also associated with CD8+ T-cell-dominant hepatitis. Consequently, achieving targeted mRNA expression in vivo emerges as a pivotal strategy to mitigate side effects and enhance efficacy, representing a fundamental aspect of next-generation LNPs.
For mRNA cancer vaccines, the targeted delivery and expression of mRNA-encoding tumor antigens in lymphoid organs offer a promising approach to improving vaccine efficacy while reducing potential side effects. Although various nanosystems can transport cargo to specific organs through the incorporation of active-targeting ligands, some limitations persist in their clinical applications.
Firstly, the introduction of targeting ligands adds complexity to the delivery system, impeding rapid vaccine production. Secondly, the successful delivery and transfection of immune cells in lymphoid organs remain challenging and are rarely reported. In our research group, we have successfully developed a series of LNPs exhibiting organ-specific targeting to the liver, spleen, and lung without the need for active targeting ligands.
In this study, we explore and employ LNP 113-O12B, designed with lymph node (LN)-targeting specificity, for the development of a therapeutic mRNA cancer vaccine. Comparative analysis with LNPs formulated using ALC-0315, a crucial component of the FDA-approved Comirnaty, revealed that 113-O12B displayed significantly reduced mRNA expression in the liver while exhibiting higher expression in LNs after subcutaneous (SC) injection.
The targeted delivery of full-length ovalbumin (OVA)-encoding mRNA vaccine markedly enhanced the CD8+ T cell response, resulting in outstanding protective and therapeutic effects against the OVA-transduced B16F10 tumor model.
Furthermore, the mRNA vaccine encoding a tumor-associated peptide antigen, TRP2180–188, demonstrated remarkable therapeutic efficacy in established B16F10 tumor models. This underscores the potential of the 113-O12B platform for various antigen types. Noteworthy advancements were achieved when combining the mRNA cancer vaccine with an anti-programmed death-1 (PD-1) antibody, further enhancing the complete response (CR) to these established tumor models. Impressively, all surviving mice from the therapeutic experiments exhibited resistance to rechallenge with a lung metastatic model, indicating the establishment of long-term antitumor immunity fostered by our mRNA cancer vaccine.
