Development of an RNAi therapeutic for alpha-1-antitrypsin liver disease
Christine I. Wooddell, … , Steven B. Kanner, Jeffrey H. Teckman
Christine I. Wooddell, … , Steven B. Kanner, Jeffrey H. Teckman
Published May 7, 2020
Citation Information: JCI Insight. 2020;5(12):e135348. https://doi.org/10.1172/jci.insight.135348.
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Research Article Hepatology Therapeutics

Development of an RNAi therapeutic for alpha-1-antitrypsin liver disease

Abstract

The autosomal codominant genetic disorder alpha-1 antitrypsin (AAT) deficiency (AATD) causes pulmonary and liver disease. Individuals homozygous for the mutant Z allele accumulate polymers of Z-AAT protein in hepatocytes, where AAT is primarily produced. This accumulation causes endoplasmic reticulum (ER) stress, oxidative stress, damage to mitochondria, and inflammation, leading to fibrosis, cirrhosis, and hepatocellular carcinoma. The magnitude of AAT reduction and duration of response from first-generation intravenously administered RNA interference (RNAi) therapeutic ARC-AAT and then with next-generation subcutaneously administered ARO-AAT were assessed by measuring AAT protein in serum of the PiZ transgenic mouse model and human volunteers. The impact of Z-AAT reduction by RNAi on liver disease phenotypes was evaluated in PiZ mice by measuring polymeric Z-AAT in the liver; expression of genes associated with fibrosis, autophagy, apoptosis, and redox regulation; inflammation; Z-AAT globule parameters; and tumor formation. Ultrastructure of the ER, mitochondria, and autophagosomes in hepatocytes was evaluated by electron microscopy. In mice, sustained RNAi treatment reduced hepatic Z-AAT polymer, restored ER and mitochondrial health, normalized expression of disease-associated genes, reduced inflammation, and prevented tumor formation. RNAi therapy holds promise for the treatment of patients with AATD-associated liver disease. ARO-AAT is currently in phase II/III clinical trials.

Authors

Christine I. Wooddell, Keith Blomenkamp, Ryan M. Peterson, Vladimir M. Subbotin, Christian Schwabe, James Hamilton, Qili Chu, Dawn R. Christianson, Julia O. Hegge, John Kolbe, Holly L. Hamilton, Maria F. Branca-Afrazi, Bruce D. Given, David L. Lewis, Edward Gane, Steven B. Kanner, Jeffrey H. Teckman

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Figure 1

RNAi-mediated reduction of Z-AAT protein and mRNA in young PiZ mouse livers prevented polymer accumulation.

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RNAi-mediated reduction of Z-AAT protein and mRNA in young PiZ mouse liv...
Five-week-old male and female PiZ mice were given IV injections of 8 mg/kg ARC-AAT API plus 8 mg/kg EX1 (RNAi-AAT + EX1) once every 2 weeks (Q2W, n = 24) or once every 3 weeks (Q3W, n = 8) or were given Q2W injections of RNAi-Control plus 8 mg/kg EX1 (RNAi-Control + EX1) (n = 6). Age-matched control animals were injected Q2W with saline (n = 13). Untreated baseline mice were euthanized at 5 weeks of age (n = 5). (A) Plasma was collected at the indicated times and Z-AAT protein measured, shown as the group mean ± SEM relative to pretreatment expression. (B) RNAi-AAT + EX1, RNAi-Control + EX1, and saline-injected mice were euthanized 2 weeks after final injection, and amounts of Z-AAT mRNA in homogenized liver tissue were quantified relative to the geometric mean of the saline group. Males were given 4 injections and euthanized when 13 weeks old. Females were given 5 injections and euthanized when 15 weeks old. (C and D) The amounts of soluble (monomeric) and insoluble (polymeric) Z-AAT protein in liver lysates of male mice at baseline (5 weeks old) or given 4 Q2W injections and euthanized when they were 13 weeks old were measured by semiquantitative Western blotting, shown relative to the saline group as the mean ± SEM, n = 3–10. (E) Representative PAS-D–stained (upper row) and H&E-stained (lower row) liver sections from male mice at baseline or injected Q2W with saline, RNAi-Control + EX1, or RNAi-AAT + EX1. Scale bars for PAS-D indicate 50 μm and for H&E indicate 20 μm. Arrows point to Z-AAT globules and arrowheads to foci of inflammatory cells.