Abstract 7249: Enhancing mRNA- lipid nanoparticles formulations to improve transfection efficiency in macrophages and dendritic cells in cancer immunotherapy
Authors: Alshehry Yasir , Fernandez Matthew , Aldaqqa Raneem , Al-Terawi Asma , Sweet Douglas , da Rocha Sandro 
Published: March 2024

Cancer poses a global health challenge, driving the quest for innovative therapies. Messenger ribonucleic acid (mRNA) lipid nanoparticles (LNPs) are a promising strategy in cancer immunotherapy. However, a major obstacle lies in efficiently transfecting immune cells like macrophages and dendritic cells (DCs) with LNPs. This study seeks to improve cancer immunotherapy by optimizing mRNA-LNP formulations. Therefore, we systematically evaluated three components of LNPs, namely ionizable lipids, phospholipids, and sterols, and fine-tuned the components and their molar ratios. A comprehensive screening process was conducted to determine the efficiency of LNPs, involving in vitro experiments on macrophages and DCs, as well as in vivo assessments. Among six ionizable lipids assessed in different cell lines (RAW264.7 and DC2.4), SM-102 significantly enhanced the transfection efficiency in macrophages and DCs. Subsequently, we evaluated these LNPs in an in vivo setting. We quantified the bioluminescence signal after administering LNPs loaded with luciferase mRNA. The results demonstrated a significant increase in luciferase expression when using SM-102 and ALC-0315 lipids. To validate this finding, we conducted a T cell response study, which revealed an increased percentage of CD8+ T cells with SM-102-based LNPs compared to other formulations. Having identified SM-102 as a potent ionizable lipid, we proceeded to evaluate three phospholipids in vitro. The results indicated a significant enhancement in transfection efficiency with DOPE lipids compared to DSPC. Consequently, we selected DOPE as the phospholipid for subsequent screening. Lastly, we explored different types of sterols with varying molar ratios in macrophages and DC cells. Our findings unveiled a notable improvement in mRNA delivery, particularly in DCs, when the molar ratio of β-sitosterol was increased to 19.5%, while concurrently decreasing the molar ratio of cholesterol to 19% within the same formulation. It is noteworthy that the addition of β-sitosterol alone led to reduced transfection efficiency in DCs but resulted in a significant enhancement in macrophages. Lastly, we evaluated the top four formulations in vivo, and the results demonstrated a significant increase when β-sitosterol was added to the formulation with cholesterol, at molar ratios of 19.5% and 19%, respectively. Overall, altering lipid composition and their molar ratios profoundly impact mRNA-LNP transfection. The optimized formulations, comprising SM-102, DOPE, and cholesterol with or without β-sitosterol, outperformed the alternatives. These refined formulations hold promise for clinical applications, potentially enhancing passive therapeutic agent delivery into macrophages and DCs, offering promising prospects for advancing cancer immunotherapy.

Citation Format: Yasir Alshehry, Matthew Fernandez, Raneem Aldaqqa, Asma Al-Terawi, Douglas Sweet, Sandro da Rocha. Enhancing mRNA- lipid nanoparticles formulations to improve transfection efficiency in macrophages and dendritic cells in cancer immunotherapy [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 7249.