Synthesis of multimeric pyrrolidine iminosugar inhibitors of human bglucocerebrosidase and a-galactosidase A: First example of a multivalent enzyme activity enhancer for Fabry disease

The synthesis of a chemical library of multimeric pyrrolidine-based iminosugars by incorporation of three pairs of epimeric pyrrolidine-azides into different alkyne scaffolds via CuAAC is presented. The new multimers were evaluated as inhibitors of two important therapeutic enzymes, human a-galactosidase A (a-Gal A) and lysosomal b-glucocerebrosidase (GCase). Structure-activity relationships were established focusing on the iminosugar inhitope, the valency of the dendron and the linker between the inhitope and the central scaffold. Remarkable is the result obtained in the inhibition of a-Gal A, where one of the nonavalent compounds showed potent inhibition (0.20 mM, competitive inhibition), being a 375-fold more potent inhibitor than the monovalent reference. The potential of the best a-Gal A inhibitors to act as pharmacological chaperones was analyzed by evaluating their ability to increase the activity of this enzyme in R301G fibroblasts from patients with Fabry disease, a genetic disorder related with a reduced activity of a-Gal A. The best enzyme activity enhancement was obtained for the same nonavalent compound, which increased 5.2-fold the activity of the misfolded enzyme at 2.5 mM, what constitutes the first example of a multivalent a-Gal A activity enhancer of potential interest in the treatment of Fabry disease.