Efficacy of Enzyme and Substrate Reduction Therapy with a Novel Antagonist of Glucosylceramide Synthase for Fabry Disease

Karen M. Ashe, Eva Budman, Dinesh S. Bangari, Craig S. Siegel, Jennifer B. Nietupski, Bing Wang, Robert J. Desnick, Ronald K. Scheule, John P. Leonard, Seng H. Cheng, John Marshall

Fabry disease, an X-linked glycosphingolipid storage disorder, is caused by the deficient activity of α-galactosidase A (α-Gal A). This results in the lysosomal accumulation of its glycolipid substrates including globotriaosylceramide (GL-3) and lysoglobotriaosylceramide (globotriaosyl lysosphingolipid, lyso-GL-3) in various cell types leading to kidney, heart, and cerebrovascular disease. To complement and potentially augment the current standard of care, biweekly infusions of recombinant α-Gal A, the merits of substrate reduction therapy (SRT) by selectively inhibiting glucosylceramide synthase (GCS) were examined. Here, we report the development of a novel, orally available GCS inhibitor (Genz-682452) with pharmacological and safety profiles that have potential for treating Fabry disease. Treating Fabry mice with Genz-682452 resulted in reduced tissue levels of GL-3 and lyso-GL-3 and a delayed loss of the thermal nociceptive response. Greatest improvements were realized when the therapeutic intervention was administered to younger mice before they developed overt pathology. Importantly, as the pharmacologic profiles of α-Gal A and Genz-682452 are different, treating animals with both drugs conferred the greatest efficacy. For example, as Genz-682452, but not α-Gal A, can traverse the blood-brain barrier, levels of accumulated glycosphingolipids were reduced in the brain of Genz-682452-treated but not α-Gal A-treated mice. These results suggest that combining substrate reduction and enzyme replacement may confer both complementary and additive therapeutic benefits in Fabry disease.