Lipid nanoparticles for the treatment of Huntington’s disease
University of British Columbia
Small interfering RNA (siRNA) is a molecule that can specifically stop the production of particular “target” proteins in the cell by binding to a particular messenger RNA (mRNA) molecule that codes for the protein. This leads to the destruction of the mRNA by enzymes and therefore the target protein is not produced. siRNA has great potential as therapeutics because they can, in theory, stop the production of any disease-causing proteins. Although promising, siRNA cannot be used as therapeutics because it is easily broken down in biological fluids, cannot travel to disease areas and cannot get into cells. We have developed lipid nanoparticles (LNP) as carriers for siRNA to overcome these issues. Here, we aim to advance LNP-siRNA systems that can stop the production of the mutant huntingtin protein in the brain for the treatment of Huntington’s disease (HD). We will investigate the role of LNP size to achieve maximum penetration of LNP-siRNA into brain tissue following intraventricular or intrathecal administration. In addition, LNP-siRNA formulations selectively targeting the mutant huntingtin gene will be administered by intraventricular or intrathecal injection in a well-established transgenic mouse model of HD, and the degree of mutant protein reduction as well as efficacy on the HD phenotypes will be assessed. In order to increase the potency of the LNP-siRNA systems, we will incorporate into LNP agents that perturb cellular processes for increasing the amount of siRNA released inside the cell.
Relevance to the acceleration of therapeutics for neurodegenerative diseases of aging
This project will provide critical proof-of-principle studies assessing the potential benefits of LNP-siRNA therapeutics in Huntington’s disease. The pre-clinical testing of these LNP-siRNA formulations in mouse models will generate important efficacy data and could enable the submission of an investigational new drug (IND) application for human clinical trials. This project will accelerate the validation of novel therapeutic approaches for Huntington’s disease and has the potential to be high-profile translational research leading to the development of effective and safe therapeutics for other neurodegenerative diseases of aging.
The proposed research will be the first demonstration of LNP delivery technology to silence the mutant huntingtin gene via intraventricular and intrathecal administration for the treatment of Huntington’s disease. Current LNP formulations in preclinical and clinical testing are typically between 50 to 80 nm in diameter. LNP smaller than 50 nm in diameter should allow deeper penetration into brain tissues. The distribution and gene silencing potency of LNP with sizes ranging from 20 to 100 nm in brain tissues will therefore be evaluated. In addition, approaches to enhance LNP retention and gene-silencing potency will be validated. Our proposed research may lead to the identification and development of alternative therapeutic brain-directed treatments for Huntington’s disease.
Over the course of this project we have engaged in a successful collaboration between the Leavitt and Cullis laboratories. We have been successful in improving the potencies of lipid nanoparticle (LNP) formulations of siRNA and creating a variety of LNP systems for the effective knockdown of several target genes. The genes of interest for this project were Huntingtin and MyoD. These genes are expressed in tissues that are hard to access and transfect with traditional reagents, specifically the brain and peripheral muscle tissue. To that end we have had great success with transfecting these tissues in vitro and in vivo. We have shown that siRNAs packaged in LNPs show greater knockdown than siRNAs delivered using traditional reagents. We have also demonstrated the ability to package additional nucleotide constructs, such as antisense oligonucleotides (ASOs) in LNP and show enhanced gene silencing.