Gene Therapy for Alpha 1-Antitrypsin Deficiency - Abstract. Alpha 1-antitrypsin (AAT) deficiency, an autosomal recessive disorder, manifests in lung as early onset panacinar emphysema. AAT functions to inhibit neutrophil elastase (NE) and other neutrophil serine proteases. AAT is produced predominantly in liver and diffuses into the lung from the circulation. Low AAT levels in AAT deficiency are associated with an imbalance between AAT and neutrophil-released proteases allowing slow destruction of the lung parenchyma. AAT deficiency is caused by mutation in the SERPINA1 gene; M alleles are normal alleles, Z (E342K) homozygotes account for >95% cases. Z AAT polymerizes in hepatocytes, limiting secretion, resulting in plasma levels 10-15% of normal. AAT inhibits serine proteases through its active site centered at methionine (M) 351 and 358. The active site methionines are modified by oxidants including cigarette smoke, air pollutants and endogenous oxidants from activated inflammatory cells, reducing AAT function. AAT deficiency therapy is currently treated with weekly infusions of AAT purified from human plasma; the infused AAT normalizes lung AAT levels, protecting alveoli from destruction. While AAT augmentation therapy reduces the rate of lung destruction, it is susceptible to oxidation, requiring excess “reserve” AAT to protect the lung. The focus of this proposal is to translate to humans gene therapy for AAT deficiency that circumvents both weekly requirements for protein therapy and the susceptibility of the therapeutic AAT to oxidation inactivation. We demonstrated that replacing M351 with valine (V) and M358 with leucine (L) on a normal M1 alanine (A)213 background provides anti-protease protection despite oxidant stress. One-time intravenous (IV) administration to mice of AAV8hAAT(AVL), a serotype 8 adeno-associated virus vector coding for the oxidation resistant variant hAAT(AVL) maintains high, dose-dependent anti-protease activity in serum and lung under oxidant stress compared with normal AAT. A toxicology study over 6 months in C57Bl/6 mice demonstrated that IV administration of AAV8hAAT(AVL) is safe. Based on the preclinical efficacy and safety data, we propose a phase 1 safety/dose ranging study, with IV administration of AAV8hAAT(AVL) at each of 3 doses to n=5 AAT Z homozygotes at each dose. The highest dose [2x1013 genome copies (gc)/kg] is ~ ½ log lower than the highest dose in the toxicity study. Aim 1, R61. Prepare and submit an Investigational New Drug package and gain approval from the FDA and other regulatory groups to initiate a Phase 1 clinical trial. Aim 2, R61. Optimize AAV8hAAT(AVL) production. Aim 3, R33. Manufacture clinical grade AAV8hAAT(AVL) for the Phase 1 safety/dose-ranging clinical trial. Aim 4, R33. Carry out a Phase 1 safety/dose-ranging clinical trial to determine the highest tolerable dose and preliminary biologic efficacy of AAV8hAAT(AVL) therapy for AAT deficiency.
