Research ArticleGene Therapy

Therapeutic liver repopulation by transient acetaminophen selection of gene-modified hepatocytes

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Science Translational Medicine  09 Jun 2021:
Vol. 13, Issue 597, eabg3047
DOI: 10.1126/scitranslmed.abg3047

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Trial by acetaminophen

Gene therapy vectors that integrate into the genome (as opposed to remaining episomal) promise sustained therapeutic effects for monogenic liver diseases in theory but typically do not integrate into sufficient numbers of hepatocytes to achieve therapeutic effects in practice. To increase therapeutic yields, Vonada et al. added a short hairpin RNA targeting Cypor, a cofactor necessary for acetaminophen metabolism, to integrating vectors to protect hepatocytes with successful transgene integration from toxicity related to acetaminophen exposure. Administration of the vector plus a moderately hepatotoxic dose of acetaminophen to neonatal mice achieved therapeutic degrees of viral vector integration in models of hemophilia B and phenylketonuria.

Abstract

Gene therapy by integrating vectors is promising for monogenic liver diseases, especially in children where episomal vectors remain transient. However, reaching the therapeutic threshold with genome-integrating vectors is challenging. Therefore, we developed a method to expand hepatocytes bearing therapeutic transgenes. The common fever medicine acetaminophen becomes hepatotoxic via cytochrome p450 metabolism. Lentiviral vectors with transgenes linked in cis to a Cypor shRNA were administered to neonatal mice. Hepatocytes lacking the essential cofactor of Cyp enzymes, NADPH-cytochrome p450 reductase (Cypor), were selected in vivo by acetaminophen administration, replacing up to 50% of the hepatic mass. Acetaminophen treatment of the mice resulted in over 30-fold expansion of transgene-bearing hepatocytes and achieved therapeutic thresholds in hemophilia B and phenylketonuria. We conclude that therapeutically modified hepatocytes can be selected safely and efficiently in preclinical models with a transient regimen of moderately hepatotoxic acetaminophen.

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