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CRISPR/Cas9-mediated in vivo gene targeting corrects hemostasis in newborn and adult factor IX knockout mice

Lili Wang, Yang Yang, Camilo Ayala Breton, John White, Jia Zhang, Yan Che, Alexei Saveliev, Deirdre McMenamin, Zhenning He, Caitlin Latshaw, Mingyao Li and James M. Wilson

Key Points

  • AAV- and CRISPR/Cas9-mediated gene targeting achieved sustained, clinically beneficial expression of hFIX in a mouse model of hemophilia B

  • As this genome editing strategy is not mutation position specific, it could be applied to the majority of patients with hemophilia B

Abstract

Many genetic diseases, including hemophilia, require long-term therapeutic effects. Despite the initial success of liver-directed adeno-associated virus (AAV) gene therapy for hemophilia in clinical trials, long-term, sustained therapeutic effects have yet to be seen. One explanation of the gradual decline of efficacy over time is that the non-integrating AAV vector genome could be lost during cell division during hepatocyte turnover, albeit at a slow pace in adults. Readministering the same vector is challenging due to the AAV neutralizing antibodies elicited by the initial treatment. Here, we investigated the use of clustered regularly interspaced short palindromic repeats (CRISPR)/Cas9-mediated homology-directed gene targeting for sustained treatment of hemophilia B. We developed a donor vector containing a promoter-less, partial human factor IX (FIX) cDNA carrying the hyperactive FIX Padua mutation. A single injection of dual AAV vectors in newborn and adult FIX-knockout (FIX-KO) mice led to stable expression of FIX at or above the normal levels for eight months. Eight weeks after the vector treatment, we subjected a subgroup of newborn and adult treated FIX-KO mice to a two-third partial hepatectomy; all of these animals survived the procedure without any complications or interventions. FIX levels persisted at similar levels for 24 weeks after partial hepatectomy, indicating stable genomic targeting. Our results lend support for the use of a CRISPR/Cas9 approach to achieve lifelong expression of therapeutic proteins.

  • Submitted March 26, 2019.
  • Revision received April 2, 2019.
  • Accepted April 1, 2019.