Blood Journal | In vivo genome editing of the albumin locus as a platform for protein replacement therapy

http://www.bloodjournal.org/content/early/2015/08/20/blood-2014-12-615492

Key points

• AAV and ZFN mediated targeting of albumin locus corrects disease phenotype in mouse models of hemophilia A and B.
• Robust expression from the albumin locus provides a versatile platform for liver directed protein replacement therapy.

Abstract

Site specific genome editing provides a promising approach for achieving long-term, stable therapeutic gene expression. Genome editing has been successfully applied in a variety of preclinical models, generally focused on targeting of the diseased locus itself; however, limited targeting efficiency or insufficient expression from the endogenous promoter may impede the translation of these approaches, particularly if the desired editing event does not confer a selective growth advantage. Here we report a general strategy for liver-directed protein replacement therapies that addresses these issues: Zinc Finger Nuclease (ZFN)-mediated site-specific integration of therapeutic transgenes within the albumin gene. Employing adeno-associated viral vector (AAV) delivery in vivo, we achieved long-term expression of human factors VIII and IX (hF.VIII and hF.IX) in mouse models of hemophilia A and B at therapeutic levels. Using the same targeting reagents in wild type mice, we expressed lysosomal enzymes that are deficient in Fabry and Gaucher diseases, as well as in Hurler and Hunter syndromes. The establishment of a universal nuclease-based platform for secreted protein production would represent a critical advance in the development of safe, permanent, and functional cures for diverse genetic and non-genetic diseases.

• Submitted December 3, 2014.
• Accepted August 8, 2015.

• Copyright © 2015 American Society of Hematology