Molecular Therapy: Methods & Clinical Development (Jun 2021)

Targeting the Apoa1 locus for liver-directed gene therapy

  • Marco De Giorgi,
  • Ang Li,
  • Ayrea Hurley,
  • Mercedes Barzi,
  • Alexandria M. Doerfler,
  • Nikitha A. Cherayil,
  • Harrison E. Smith,
  • Jonathan D. Brown,
  • Charles Y. Lin,
  • Karl-Dimiter Bissig,
  • Gang Bao,
  • William R. Lagor

Journal volume & issue
Vol. 21
pp. 656 – 669

Abstract

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Clinical application of somatic genome editing requires therapeutics that are generalizable to a broad range of patients. Targeted insertion of promoterless transgenes can ensure that edits are permanent and broadly applicable while minimizing risks of off-target integration. In the liver, the Albumin (Alb) locus is currently the only well-characterized site for promoterless transgene insertion. Here, we target the Apoa1 locus with adeno-associated viral (AAV) delivery of CRISPR-Cas9 and achieve rates of 6% to 16% of targeted hepatocytes, with no evidence of toxicity. We further show that the endogenous Apoa1 promoter can drive robust and sustained expression of therapeutic proteins, such as apolipoprotein E (APOE), dramatically reducing plasma lipids in a model of hypercholesterolemia. Finally, we demonstrate that Apoa1-targeted fumarylacetoacetate hydrolase (FAH) can correct and rescue the severe metabolic liver disease hereditary tyrosinemia type I. In summary, we identify and validate Apoa1 as a novel integration site that supports durable transgene expression in the liver for gene therapy applications.

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