J.C. Kaczmarek, K.J. Kauffman, A.K. Patel, M.W. Heartlein, F. DeRosa, D.G. Anderson
Keywords: mRNA, therapeutic nanoparticles, nucleic acid delivery
Summary:The recent success of Alnylam’s Phase III clinical trials with patisiran, an siRNA-loaded lipid nanoparticle, has injected fresh optimism into the field of nanoparticle-mediated nucleic acid delivery. Nanoparticle encapsulation has long been used to deliver therapeutic nucleic acids owing to its ability to protect the nucleic acid cargo from in vivo degradation, promote extended circulation in the blood, and facilitate cellular uptake and endosomal escape. The delivery of mRNA, in particular, has recently been the subject of widespread research efforts, thanks in large part to advances in the in vitro transcription of more stable, potent mRNA constructs. One of the major advantages to using mRNA as a means of protein therapy as opposed to the more traditionally studied plasmid DNA is that mRNA need not reach the nucleus in order to be effective, hence allowing for higher potency and more precise temporal control of protein expression. Unsurprisingly, many groups have made use of nanoparticle technologies previously used to deliver siRNAs to also deliver mRNAs, but the larger size of mRNA and the fundamentally different subcellular pathways of mRNA translation and siRNA mediated silencing have prompted research into designing nanoparticle formulations specifically tailored to mRNA delivery. In this work, we demonstrate that poly(β-amino esters), a class of biodegradable polymers originally designed to deliver DNA, are capable of successful intravenous mRNA delivery in mice following non-covalent formulation with a stabilizing agent (polyethylene glycol-lipid conjugates). Systemic injection with these nanoparticles results in specific mRNA expression in the lung, as opposed to lipid nanoparticles which are generally most effective in the liver. Additionally, we show that experimental design methods can be implemented to optimize polymer synthesis and nanoparticle formulation, resulting in a nanoparticle that is multiple orders of magnitude more effective at delivering mRNA in vivo compared to both the original nanoparticle as well as a commercially available polymeric transfection reagent. Experiments with a transgenic mouse model revealed successful mRNA translation following nanoparticle delivery in lung endothelial, epithelial, and immune cells, suggesting these optimized nanoparticles have the potential to treat a variety of lung disorders.