Long-Term Attenuation of Vascular Hyperpermeability in a Hereditary Angioedema Mouse Model by Adenine Base Editing

Background
Hereditary angioedema (HAE) is a rare and potentially life-threatening disorder caused by dysregulated kallikrein–kinin signaling and bradykinin-induced vascular hyperpermeability. Current therapies targeting this pathway are effective but require lifelong administration, underscoring the need for durable and potentially curative interventions. Adenine base editors (ABEs), engineered from CRISPR/Cas systems, enable precise single-nucleotide modifications with minimal genomic disruption, offering a promising strategy for long-term gene silencing.

Methods
NG-ABE8e was delivered via AAV8 or lipid nanoparticles (LNP) to disrupt the exon 2 splice donor site of Klkb1 in Serping1+/− mice. Editing outcomes were quantified by high-throughput sequencing; serum kallikrein levels were measured by ELISA; and vascular permeability was evaluated using Evans blue dye extravasation, fluorescent tracer leakage, and VE-cadherin immunostaining. Safety evaluations included off-target analysis, histopathology, serum biochemistry, activated partial thromboplastin time (aPTT), and systemic hemodynamic stability.

Results
AAV8-NG-ABE8e induced > 60% A•T-to-G•C conversion at the target site, promoting exon 2 skipping and reducing Klkb1 mRNA and serum kallikrein levels by > 85%, an effect sustained for at least 1 year. AAV8-NG-ABE8e also reversed bradykinin-driven vascular hyperpermeability and attenuated inflammatory gene signatures. Prolongation of aPTT was observed only when circulating kallikrein levels declined below 2 μg/mL. Similarly, LNP-mediated delivery of NG-ABE8e mRNA resulted in > 90% reductions in Klkb1 expression and serum kallikrein levels. No evidence of significant long-term toxicity was detected.

Conclusion
These findings demonstrate that, in a murine model, NG-ABE8e–mediated disruption of Klkb1 enables durable suppression of serum kallikrein and vascular stabilization, suggesting its potential as a promising single-intervention strategy for the treatment of HAE.