Gene therapy for Fabry disease

Fabry disease is an X‐linked metabolic disorder caused by a deficiency ofα‐galactosidase A (α‐Gal A). Lack of this lysosomal hydrolase results in theaccumulation of galactose‐terminal glycosphingolipids in a number of tissues, including vascular endothelial cells. Premature death is predominantly associated withvascular conditions of the heart, kidneys and brain. Historically, treatment has largelybeen palliative. Alternative treatments for many lysosomal storage diseases have beendeveloped, including allogeneic organ and bone marrow transplantation, enzymereplacement therapy, and gene therapy. Significant clinical risks still exist withallogeneic transplantations. α‐Gal A enzyme replacement therapy has beenimplemented in clinical trials. This approach has been effective but may havelimitations for long‐term systemic or cost‐effective correction. As an alternative, genetherapy approaches, involving a variety of gene delivery systems, have been pursuedfor the amelioration of Fabry disease. Fabry disease is a compelling disorder for genetherapy, as target cells are readily accessible and relatively low levels of enzymecorrection may suffice to reduce storage. Importantly, metabolic cooperativity effectsare also manifested in Fabry disease, wherein corrected cells secrete α‐Gal A that cancorrect bystander cells. In addition, a broad therapeutic window probably exists, andmouse models of Fabry disease have been generated to assist studies. As an example, in vitro and in vivo studies using α‐Gal A‐transduced haematopoietic cells from Fabrymice have demonstrated enzymatic correction of recipient cells and dissemination ofα‐Gal A upon transplantation, leading to reduced lipid storage in a number ofclinically relevant organs. This corrective enzymatic effect has recently been shown tobe even further enhanced upon pre‐selection of therapeutically transduced cells priorto transplantation. This review will briefly detail current gene delivery methods andsummarize results to date in the context of gene therapy for Fabry disease.