Abstract

Exploiting Non-Animal Models to Optimize Lipid Nanoparticle/mRNA Complexes as Heart Therapeutics

Kevin Healy, Jan Fandrianto and Selfia Halim Distinguished Professorship in Engineering, University of California, Berkeley

Although cardiovascular disease is the leading cause of death worldwide, innovation in heart failure therapeutics has been sparse. A primary reason behind the lack of therapeutic development is the inability to use phenotypic tissue-level approaches to discover novel therapies, such as complex in vitro models like microphysiological systems (MPS). In recent years, therapeutics that increase the expression of specific genes have been explored, but they have limited clinical translatability due to the lack of a safe and effective delivery system. A notable obstacle is that dense cardiac tissues suffer from low transfection efficiency of non-proliferative cardiomyocytes, diffusional barriers posed by the extracellular matrix of 3D cardiac muscle, and potential immunogenicity and carcinogenicity associated with viral vectors. Recent progress in the development of non-viral vectors like lipid nanoparticles (LNPs) holds great promise in overcoming these limitations and can make a breakthrough in cardiovascular medicine due to the transient nature of mRNA transfection. A key challenge preventing the development of LNPs that can transfect heart tissue is the absence of in vitro screening platforms that predict in vivo efficacy. In this talk, I will demonstrate that a phenotypic tissue-level cardiac MPS containing a heart micromuscle constructed from human induced pluripotent stem cell cardiomyocytes (hiPSC-CM) with a Cre-reporter, can identify LNP/mRNA complexes that diffuse within 3D cardiac micromuscle, transfect cardiomyocytes, and predict LNP transfection in the heart in vivo. Specifically, formulations contained a novel acid-degradable PEG (ADP)-lipid that had enhanced diffusion and gene editing efficiency in the cardiac MPS. In vivo delivery of LNP/mRNA complexes containing luciferase and CRE mRNA into Ai6 mice validated the MPS screening results and demonstrated that ADP-LNPs exhibited significantly higher transfection in the heart, with lower off-target levels of liver uptake compared to a standard LNP formulation. To our knowledge, this is the first study incorporating an organ-on-a-chip microfluidic culture device as a platform for screening novel LNP formulations and successfully identifying one suitable for delivery of mRNA to the heart. Our work will contribute to the progress of new cardiac therapies, and will stimulate the generation of more advanced non-animal models as preclinical platforms in the drug discovery landscape.