Adenine Base Editor for Gene Correction Without Double-Strand Breaks
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Solution Overview
Problem
Current treatments for monogenic disorders like mucopolysaccharidosis type I storage disease are limited, with enzyme replacement therapy and hematopoietic stem cell transplantation having significant side effects and not addressing musculoskeletal and cardiac pathologies effectively, and existing gene editing methods like CRISPR-HDR being inefficient and prone to mutagenesis.
Innovation Solution
The use of an adenine base editor (ABE) complex comprising a modified TadA enzyme, a catalytically impaired Cas9 protein, and a guide RNA that converts adenine to guanine in the IDUA gene to correct the W402X mutation, thereby restoring enzyme activity without inducing double-strand breaks or requiring homologous recombination, using delivery methods such as viral vectors and nanoparticles for prenatal or postnatal administration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If CRISPR-HDR is used for gene editing, then gene correction can be achieved, but the method is inefficient and requires double-strand breaks that cause unwanted mutagenesis and large deletions
Solution Approach 1:
The patent replaces the mechanical DNA breakage and repair system (CRISPR-Cas9 HDR) with a chemical base modification system (adenine base editor). Instead of creating double-strand breaks that require cellular repair machinery, the invention uses a catalytically impaired Cas9 fused to an adenine deaminase enzyme to directly chemically convert adenine to inosine at the target site, which is then recognized as guanine during DNA replication. This substitution eliminates the harmful mechanical breakage while achieving precise gene correction.
Solution Approach 2:
The patent changes the fundamental parameter of the gene editing mechanism from physical DNA cleavage to chemical base modification. By using a catalytically impaired Cas9 (nickase or dead Cas9) that cannot create double-strand breaks but can still bind and recruit the adenine deaminase enzyme to the target site, the system transforms the editing process from a destructive-repair model to a direct chemical conversion model, thereby eliminating mutagenesis and large deletions while maintaining editing precision.
2Reliability
If enzyme replacement therapy is used to treat MPS-IH, then IDUA enzyme activity can be restored, but the treatment is costly and has significant immunogenic side effects
Solution Approach 1:
The patent applies preliminary action by performing gene editing in utero or in early infancy before the disease progresses and before the patient's immune system develops strong memory responses. By correcting the IDUA gene mutation early in development, the patient's own cells begin producing functional IDUA enzyme endogenously, establishing long-term enzyme activity before immunogenic complications can arise from repeated exogenous enzyme administrations.
Solution Approach 2:
The patent enables the patient's own cells to produce the needed IDUA enzyme through genetic correction, rather than requiring lifelong dependence on exogenous enzyme replacement therapy. The corrected cells continuously self-produce functional enzyme, eliminating the need for repeated costly infusions and avoiding the immunogenic responses associated with continuous external enzyme administration.
3Reliability
If hematopoietic stem cell transplantation is performed, then IDUA enzyme activity can be restored, but the procedure is limited by donor availability and has complications from myeloablation and immunosuppression
Solution Approach 1:
The patent extracts the essential function of hematopoietic stem cell transplantation (restoring IDUA enzyme activity) while eliminating the complex and harmful procedural elements (myeloablation, immunosuppression, donor matching). By directly editing the patient's own hematopoietic stem cells or other accessible cells in vivo, the invention achieves enzyme restoration without requiring donor cells or the dangerous conditioning regimens associated with transplantation.
Solution Approach 2:
The patent introduces an intermediary delivery system (viral vectors or nanoparticle carriers) that mediates the delivery of base editor components to target cells in vivo. This intermediary approach allows for non-invasive or minimally invasive administration compared to transplantation surgery, enabling gene correction in accessible cell populations without requiring stem cell harvesting, transplantation procedures, or post-transplant immunosuppression management.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach effectively corrects the IDUA gene mutation, ameliorating symptoms of Hurler syndrome and other lysosomal storage diseases by enhancing enzyme activity and reducing tissue accumulation of glycosaminoglycans, improving cardiac and skeletal health, and offering a safer alternative to traditional gene editing methods with reduced off-target effects.
Implementation Method 1
The adenine base editor (ABE) complex comprises a modified TadA enzyme, a catalytically impaired Cas9 protein and a guide RNA (sgRNA) which directs said ABE complex to the mutated target DNA molecule, which upon contact converts adenine in said mutation to inosine, thereby catalyzing an A-T to G-C transition following DNA replication
Data Source
AI summary
A method for in utero and postnatal genome editing of a lysosomal storage disease gene, the method comprising administering to a subject an ABE or CBE complex, wherein the subject is an embryo, a fetus, a neonate, a child or an adult, ABE or CBE complex comprising CRISPR-mediated base editor and a guide RNA (gRNA), the gRNA targeting a mutation in a therapeutic gene; and introducing a modified codon in the therapeutic gene by base editing the therapeutic gene without inducing double strand DNA breaks, wherein the base editing is performed by the adenoviral vector, an adeno-associated viral vector, nucleoprotein complex or an mRNA in a lipid based nanoparticle.