Key Findings
The in vivo gene-editing system demonstrated high therapeutic efficacy across multiple cancer models. In mice with B-cell acute lymphoblastic leukemia, a single injection resulted in complete responses in 18 of 20 animals across four human immune-cell donors. In multiple myeloma models, all eight treated mice achieved complete responses, with three of four animals maintaining disease control after a subsequent tumor challenge. The system also showed activity against solid tumors; in a sarcoma model, complete responses were observed in five of six animals from one donor and three of eight from another.
Technical Details
The approach utilizes a two-vector delivery system to engineer human T cells in vivo:
- Enveloped Delivery Vehicles (EDVs): Modified to target CD3, these vehicles transport CRISPR–Cas9 ribonucleoproteins.
- Adeno-Associated Viruses (AAVs): An engineered variant, AAV-hT7, delivers DNA templates for gene insertion. AAV-hT7 is designed to resist pre-existing neutralizing antibodies and enhance uptake by human T cells.
The system integrates the CAR transgene into the T cell receptor alpha constant (TRAC) locus, ensuring CAR expression is regulated by endogenous machinery rather than random integration. In humanized mouse models, this process generated CAR-expressing cells representing up to 19.7 percent of splenic T cells and caused complete depletion of B cells.
Background & Context
Conventional CAR T cell therapy requires a complex and costly process of extracting patient cells, modifying them in a laboratory, and reinfusing them. This new method aims to bypass these constraints by performing the engineering directly within the patient’s body. In a direct comparison, this CRISPR-based approach achieved complete tumor control in all six mice, demonstrating greater antitumor activity than in vivo lentiviral CAR T cell engineering.
Significance & Outlook
This platform suggests that precise in vivo genome editing can reduce manufacturing complexity and provide better control over transgene expression. However, the technology is currently at a preclinical stage. Because immunodeficient mouse models limit the assessment of safety, biodistribution, and immunogenicity, further testing in larger, immunocompetent animals, including nonhuman primates, is required before clinical translation.
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