Liver-directed promoterless gene targeting without the use of nucleases as a potential therapy for Fabry disease

Fabry disease (FD) is a rare X-linked lysosomal storage disorder caused by mutations in the alpha-galactosidase A (GLA) gene. The first symptoms may appear in childhood or adolescent (as early as 2 years of age), with systemic accumulation of glycosphingolipids in lysosomes, progressive multi-organ failure, and eventually death. The only specific treatment consists in the administration of a recombinant enzyme (produced in a laboratory), a procedure called Enzyme Replacement Therapy (ERT). ERT has several limitations, such as development of antibodies against the recombinant enzyme affecting efficacy, and high costs, about€200,000 per patient-year.
We will permanently modify the genome of hepatocytes, in such a manner that the GLA enzyme will be produced at very high levels and secreted into the bloodstream, converting the liver into a bio-factory. The target organs will then capture the circulating enzyme, as it occurs with ERT. To demonstrate the efficacy of the treatment, we will use a mouse model of Fabry disease. Those animals have inactivated the GLA gene and accumulate glycosphingolipids in lysosomes, the main causative feature of the human disease.

To support the potential translation of the approach to a human scenario, we test the procedure in primary cultures of human hepatocytes and in chimeric mice having human hepatocytes.

Our preliminary data is very encouraging and we expect the approach will be effective to cure Fabry mice and could be potentially translated to the clinic, also to juvenile patients, with a substantial reduction in the costs, and increased safety and efficacy.