A Compact Base Editor Rescues AATD-associated Liver and Lung Disease in Mouse Models.

Area of Science:

• Molecular Biology
• Genetic Engineering
• Gene Therapy

Background:

• Alpha-1 antitrypsin deficiency (AATD) results from a SERPINA1 gene mutation (PiZ), leading to AAT protein misfolding, liver sequestration, and lung emphysema.
• Current treatments for AATD primarily manage symptoms, highlighting the need for therapies targeting the genetic cause.

Purpose of the Study:

• To evaluate the efficacy of a compact adenine base editor (ABE) system delivered via a single adeno-associated virus (AAV) for correcting the PiZ mutation.
• To assess the therapeutic potential of ABE in mitigating both liver and lung pathology in preclinical models of AATD.

Main Methods:

• Development of an all-in-one ABE system utilizing an evolved Cas9 nickase (eNme2.C) and optimized deaminase components (TadA8e/TadA9e).
• In vitro testing in PiZ reporter cells to determine editing efficiency and bystander effects.
• In vivo studies in PiZ transgenic and AAT-null;PiZ transgenic mouse models to assess ABE delivery, editing rates, and physiological improvements.

Main Results:

• The eNme2.C-based ABE achieved significant on-target editing in reporter cells and PiZ transgenic mice (approx. 20-23% efficiency).
• ABE treatment reduced liver disease burden in PiZ mice and restored serum AAT levels to therapeutic levels (>570 μg/mL) in AAT-null;PiZ mice.
• Significant correction of lung function was observed in AAT-null;PiZ mice with emphysema following ABE treatment.

Conclusions:

• A single AAV-packaged eNme2.C-based ABE system effectively corrects the PiZ mutation in vivo.
• This gene editing approach demonstrates therapeutic potential for both liver and lung manifestations of AATD, paving the way for clinical translation.