mRNA Delivery with Acid Degradable Lipid Nanoparticles

• New acid degradable linkages
• Endosomal disruption with acid degradable lipids
• mRNA delivery to non-liver organs with acid degradable lipids
• mRNA delivery in the brain with acid degradable lipid nanoparticles

In this presentation I will describe a new acid degradable linkage developed in the laboratory, which has a unique combination of rapid hydrolysis at pH 5.0 and stability at pH 7.4. Acid degradable linkages (ADLs) have great potential for developing endosomal disruptive agents, due to their ability to degrade in the acidic environment of endosomes. However, ADLs need to hydrolyze on the timescale of minutes at pH 5.0 to be successful, and are consequently unstable and difficult to synthesize. In this presentation, a new acid degradable linkage will be described, composed of an azide acetal, which has a t1/2 < 5 minutes at pH 5.0 and a t ½ of > 1000 minutes at pH 7.4. The azide acetal is composed of a benzaldehyde acetal that has an azide in its para position, and has a low kH, due to the low electron donating character of its azide. However, the azide acetal can be reduced to an amine, via DTT, prior to administration, and this accelerates its hydrolysis rate 1,000 fold. We demonstrate here that the azide acetal can generate lipid nanoparticles that rapidly de-PEGylate in endosomes, which are exceptionally efficient at delivering mRNA to cells in culture and in vivo. We anticipate numerous applications of the azide acetal given its unique combination of stability at pH 7.4 and rapid hydrolysis at pH 5.0.

Professor Niren Murthy, Professor of Bioengineering, University of California at Berkeley