Enzyme Therapy for Fabry Disease Patients

Calhoun, David

Abstract

Fabry disease is an X-linked inborn error of glycolipid metabolism caused by a deficiency of the lysosomal enzyme, alpha- galactosidase A. In affected males this leads to early death due to occlusive disease of the heart, kidney and brain. The lack of sufficient quantities of purified enzyme has prevented a complete evaluation of the potential efficacy of enzyme replacement therapy in Fabry disease. In order to obtain large quantities of this enzyme, the investigator previously constructed baculovirus derivatives that produce the human enzyme. The recombinant enzyme is produced at high levels, is active with the natural in vivo substrate, trihexosylceramide, is glycosylated, and the purified recombinant enzyme is taken up by normal and Fabry fibroblasts in cell culture. In this application, the investigator proposes to determine if production of the recombinant enzyme can be increased to levels that will permit large scale production suitable for clinical trials. More specifically, the investigator proposes: (1) to optimize the level of expression of the recombinant baculovirus that produces the human alpha-galactosidase A; (2) to clone the gene encoding the human alpha-galactosidase A into more recently constructed baculovirus vectors that have more efficient expression due to the presence of enhancers and related vector improvements; (3) to analyze the carbohydrate present on the recombinant human alpha-galactosidase A enzyme produced in insect cells; and (4) to adapt the current purification scheme to the PerSeptive Biosystems BioCAD HPLC Workstation of the type used in GMP production. The successful use of enzyme replacement therapy for patients with Gaucher's disease, which is another lysosomal storage defect, provides a strong precedent for this approach for Fabry disease in a future Phase II SBIR proposal. Other issues regarding clinical end points, enzyme dose, and treatment regimen will be addressed in a potential Phase II SBIR proposal.