Accelerated Development of Nonviral Vehicles Delivering mRNA to Microglia Expressing Base Editors for Mutation-Independent Treatment of ALS
Abstract
Background: We harness next-generation gene editing molecular tools (known as base editors) delivered as messenger RNA (mRNA) loaded into nanoparticle vehicles to produce innovative treatments for ALS that slow disease progression in diagnosed patients. Base editors improve traditional gene editing technology based on CRISPR (Clustered Regularly Interspaced Short Palendromic Repeats) and CRISPR-associated protein 9 (Cas9). While CRISPR-Cas9 gene editors can cut and paste segments of a gene, base editors have improved precision and can create specific single nucleotide base (i.e., A, T, C, or G) edits, reducing off-target and unintended changes to patient genes. In addition, base editors have improved editing efficiency since they work in cells regardless of whether the cell is actively dividing, whereas first generation CRISPR-Cas9 editors require a cell to be dividing to make a precise gene edit on par with base editors. Our base editing technology has already shown efficacy for treating ALS in mice using a virus (adeno-associated virus, AAV) to deliver the base editor. This approach is advancing toward pre-IND (Investigational New Drug application) enabling studies for safety and efficacy in non-human primates (NHP). However, there are some risks associated with using viruses to deliver base editors. One of the biggest drawbacks to using AAVs to deliver gene editors is the immunogenicity challenge. According to some studies, as much as 90% of the population has pre-existing immunity to AAVs, reducing AAV safety and efficacy for therapeutic use. Second, AAVs deliver DNA, which causes the cell to continue to produce the base editor molecule even after the gene edit has been made, resulting in an immunogenic reaction to the base editor. However, mRNA delivery results in a much shorter, transient production of the base editor molecule, allowing both the mRNA and base editor to be cleared quickly after the gene edit occurs, i.e. hit-and-run editing. Since AAVs are unable to deliver mRNA, we will use polymer nanoparticle (PNP) to deliver our base editor to glial cells as messenger RNA (mRNA). Gene editing with mRNA-loaded nanoparticles has shown recent success, a prime example being Intellia s drug NTLA-2001, which showed an 87% reduction in its target disease-causing protein for a hereditary neurological disease called ATTR, marking the first clinical results for gene editing in an adult human. Analogously, our therapeutic uses mRNA to encode for a base editor that will reduce SOD1 protein, providing rationale for the success of our proposed therapeutic. Type of ALS patients helped: Our therapeutic will slow disease progression in ALS patients diagnosed with SOD1-linked ALS, a type of ALS linked with a mutation in the SOD1 gene, resulting in the abnormal SOD1 protein that causes neurotoxicity, paralysis, and death. The therapeutic uses base editors to make a single base edit in a precise segment of the gene coding for the SOD1 protein in specific cells in the spinal cord, called glial cells. The single base edit will effectively shut off production of abnormal SOD1 in these glial cells, ultimately slowing the progression of the disease, and providing a longer and improved quality of life to ALS patients. Unlike previous SOD1-linked ALS gene therapies, our therapeutic is not limited to a specific type of gene mutation, as it shuts off the gene at a gene segment not associated with any of the >150 different SOD1 mutations. Potential clinical applications, benefits, and risks: One benefit of our base editors is that they can edit the DNA of the target cells, resulting in permanently shutting off the SOD1 gene, leading to a much longer-lasting therapeutic effect with a single dose. Previous treatments for SOD1-linked ALS were based on older gene therapy molecules, such as antisense oligonucleic acids (ASOs) and short interfering RNA (siRNA), and required multiple doses. This change can provide improved
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Dec 28, 2022
- Source ID
- W81XWH2210594
Entities
People
- Anthony Duong
Organizations
- Battelle Memorial Institute
- United States Army