Single-Injection Gene Editing Achieves 64% Liver Editing with Zero Off-Target Effects
A next-gen virus-like particle system delivers precise cytosine base editing in mouse liver and retina, with strong therapeutic results in disease models.
Summary
Researchers at ShanghaiTech University and Fudan University have engineered a powerful new gene-editing delivery system using virus-like particles (VLPs) to carry cytosine base editors into living mice. The key breakthrough was identifying why previous attempts at in-body cytosine editing failed — the editing machinery was being sabotaged by enzymes called uracil DNA glycosylases. By redesigning the editor to better block these enzymes, the team achieved remarkably high editing rates: up to 64% in the liver and 24% in the retina with a single injection. No detectable off-target edits were found, outperforming conventional delivery methods like AAV viral vectors and lipid nanoparticles. This advance could accelerate gene therapies for age-related conditions including high cholesterol, liver metabolic disease, and eye disorders.
Detailed Summary
Gene editing holds enormous promise for treating age-related diseases at their root cause, but delivering editing tools safely and efficiently into living tissue has remained a major obstacle. Virus-like particles — engineered protein shells that mimic viruses without carrying infectious genetic material — have emerged as a promising delivery vehicle, but until now their performance for cytosine base editing inside living organisms was disappointingly low.
Researchers from ShanghaiTech University and Fudan University identified the culprit: enzymes called uracil DNA glycosylases (UDGs) were destroying the edited DNA before changes could take hold. To solve this, they redesigned a cytosine base editor called the transformer base editor (tBE) and engineered a VLP delivery system that vastly improves recruitment of UDG inhibitor proteins — essentially shielding the edits from enzymatic erasure.
The results in mice were striking. A single injection of tBE-VLPs achieved an average of 46% editing at the Pcsk9 gene (a major cholesterol-regulating target) and 64.2% at the Hpd gene in the liver, as well as 24.2% editing in retinal pigment epithelium cells — all producing meaningful therapeutic effects in mouse disease models. Critically, no detectable off-target edits were found in either cell cultures or living animals, and precision surpassed that of AAV vectors and lipid nanoparticle mRNA delivery systems.
For longevity medicine, these targets are highly relevant. PCSK9 inhibition is a validated strategy for lowering LDL cholesterol and cardiovascular risk. HPD is involved in liver metabolic pathways, and VEGFA drives pathological blood vessel growth in age-related macular degeneration and other conditions.
Caveats include that all experiments are currently in mice only, the full paper is not open access, and some co-authors have commercial conflicts of interest through CorrectSequence Therapeutics. Human translation will require extensive safety validation.
Key Findings
- Single injection of tBE-VLPs achieved 64.2% gene editing efficiency at liver Hpd and 46% at Pcsk9 in mice.
- 24.2% editing of VEGFA in retinal pigment epithelium achieved with no detectable off-target mutations.
- UDG enzyme interference was identified as the root cause of poor in vivo cytosine base editing efficiency.
- tBE-VLP4 outperformed AAV and lipid nanoparticle delivery in both efficiency and specificity.
- Therapeutic benefits confirmed in mouse disease models for liver metabolic disease and retinal conditions.
Methodology
The study used engineered virus-like particles loaded with a redesigned cytosine base editor (tBE) in mouse models targeting liver (Pcsk9, Hpd genes) and retina (Vegfa gene). Editing efficiency and off-target profiles were assessed both in vitro and in vivo. Comparisons were made against AAV and lipid nanoparticle mRNA delivery systems.
Study Limitations
All experiments were conducted in mice; human efficacy and safety remain unproven. Full paper is behind a paywall, so this summary is based on the abstract only. Three co-authors are scientific cofounders of CorrectSequence Therapeutics, a commercial gene-editing company, representing a potential conflict of interest.
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