UBC Theses and Dissertations
Lipid nanoparticles for delivery of nucleic acid therapeutics Chen, Sam
Nucleic acid therapies have the potential to enable the treatment of disorders previously untreatable. However, significant barriers prevent the rapid development of nucleic acid therapeutics and necessitate the use of sophisticated delivery systems. The overall objective of this dissertation is to develop more effective and tolerable lipid nanoparticles (LNPs) for nucleic acid delivery. Specifically, LNP that vary in size, stability and composition were tested for activity after subcutaneous and intravenous injection in order to optimize LNP properties. Furthermore, the incorporation of novel lipophilic pro-drugs co-delivered with nucleic acids was explored as a means to improve tolerability. The first part of this dissertation explores the use of subcutaneous administration for LNP-siRNA. There are compelling reasons to develop LNP-siRNA that can be administered subcutaneously. These include the potential for self-administration, a prolonged therapeutic window due to a depot effect and access to cell types that are in contact with the lymphatic system, in addition to tissues available through the circulation. We found that particle size and PEG steric barrier are both important for drainage from the injection site and subsequent accumulation in the liver. Although small LNP exhibited improved drainage and access to the systemic circulation, activity was impaired. The second part of this dissertation addresses this issue. The decrease in LNP activity can be attributed to the pronounced size dependent instability of LNP. By altering the amino-lipid content and the PEG-lipid used, the activity and stability of these systems can be greatly improved. The previous two parts of this dissertation identified limitations to existing LNP systems. First, administration of LNP containing nucleic acids could result in immune stimulation. Second, efforts to improve LNP activity must go beyond existing components. The last part of this dissertation proposes a general pro-drug strategy for enabling direct incorporation of additional compounds into the LNP. As an example dexamethasone, a corticosteroid commonly used to minimize infusion-related reactions, was used. Direct incorporation greatly improved the ability of dexamethasone to ameliorate immune stimulation by LNP containing nucleic acids. This work shows that when appropriately designed, LNP systems can have improved activity and tolerability, potentially expanding its clinical utility.
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