An RNA Editing Approach for the Treatment of Alpha-1 Antitrypsin Deficiency (AATD)

<bold>Introduction:</bold> Severe AATD is caused by a Z mutation in the SERPINA1 gene that leads to misfolding and aggregation of mutant Z-AAT protein in the liver, a decrease in functional serum AAT, and chronic obstructive pulmonary disease (COPD). <bold>Objective:</bold> We evaluated WVE-006, an investigational N-Acetylgalactosamine (GalNAc)-conjugated RNA editing oligonucleotide, in preclinical models to assess RNA editing as a potential treatment for AATD. <bold>Methods:</bold> WVE-006, which was designed to correct the Z mutation in SERPINA1 RNA, was administered to transgenic mice that express human mutant SERPINA1. We used hybridization-ELISA to measure concentrations of WVE-006 in liver, Sanger sequencing to quantify RNA editing, ELISA to quantify total serum AAT, mass spectrometry to determine proportion of wild-type AAT and Z-AAT in serum, and an in vitro neutrophil elastase inhibition assay to measure AAT function. <bold>Results:</bold> WVE-006 induced dose-dependent SERPINA1 editing after a single dose. The highest measured levels of RNA editing (23.6-58.0%) and serum AAT (26.7-40 µM) occurred 3-5 days after dosing. After repeat dosing (10 mg/kg, 7 biweekly doses), WVE-006 directed ~50% editing of the Z transcript and increased total serum AAT protein from ~8 mM to ~30 mM. At baseline, Z-AAT was the only isoform of AAT detected. After treatment, wild-type AAT accounted for ~50% of total serum AAT, and serum from treated mice displayed a ~3-fold improvement in neutrophil elastase inhibition relative to controls. <bold>Conclusions:</bold> WVE-006 directed editing of SERPINA1 RNA in the mouse liver, which led to the production of functional M-AAT protein, with total AAT in serum reaching levels higher than the 11µM threshold believed to lower risk for COPD.