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Glycodrugs: new strategies for controlling the activity of glycosidase enzymes and their application in therapies for lysosomal storage diseases and cancer

Final Report Summary - GLYCODRUGS (Glycodrugs: new strategies for controlling the activity of glycosidase enzymes and their application in therapies for lysosomal storage diseases and cancer)

Researcher: Dr. Elena M. Sánchez-Fernández. e-mail address: elmasanfer@yahoo.es
esanchez4@us.es
Co-ordinator of the Project: Prof. Carmen Ortiz Mellet. e-mail address: mellet@us.es

European Union Seventh Framework Programme (FP7-People-2012-CIG).
Grant agreement number 333594, Marie Curie Reintegration Grant.
Institution: University of Seville (Spain).

Project title: “Glycodrugs: new strategies for controlling the activity of glycosidase enzymes and their application in therapies for lysosomal storage diseases and cancer.”

The main objectives of the project are aimed at:
1) Developing applications of specific inhibitors of neutral alpha-glucosidases in anticancer therapies.
2) Reaching the preclinical stage of pharmacological chaperones for the treatment of Gaucher disease and extending the approach to other lisosomal storage diseases (LSDs).

Cancer development is often due to perturbations in the cell cycle that lead to unlimited proliferation. Since a typical feature of malignant transformations is the aberrant glycosidation of cell surface glycoproteins, selective inhibitors of the endoplasmic reticulum neutral alpha-glucosidases, involved in the early stages of N-glycoprotein biosynthesis, have attracted special attention for the development of anticancer glycotherapies. Our approach involves the use of specific inhibitors of these enzymes in order to decrease this massive glycosylation, reducing cell proliferation.
Iminosugars are glycomimetics where the oxygen has been replaced by a nitrogen atom. These compounds behave as glycosidase inhibitors and have great therapeutic potential. However, the problem with these compounds is the low anomeric selectivity resulting in serious problems for their clinical applications. To solve these problems, our research group has reported in the last years that castanospermine analogues with pseudoamide functionalities (sp2-iminosugars) exhibited high alpha-anomeric selectivity in the inhibition of glucosidases.

During the development of the project we have focused on the aglycone effect of these sp2-iminosugars (with different configuration) by introducing pseudoanomeric substituents of different nature and a library of new sp2-iminosugars has been presented for structure-activity studies that, in turn, has allowed the identification through in vitro assays of more effective anticancer drugs. Both the flexibility of the synthetic method of the starting iminosugars and their structural variability as well as the high stereoselectivity of the glycosylation reaction observed justify the synthesis of the synthesized compounds in this project and provide a unique tool for development thereof. All the compounds were next evaluated against model cell lines of different types of cancer (lung, breast, colon, cervix) by high-throughput screening and notable results were obtained with the S-dodecylglycoside and its oxidized analogues (GI50 values around 10-20 micromolar for all the cell lines tested) behaving as broad spectrum anti-proliferative agents.

Likewise new strategies have been implemented in order to synthesize the alpha-O-glycosylaminoacids with sp2-iminosugar structure (Tn antigen mimics) as building blocks for the synthesis of the corresponding alpha-O-glycopeptidomimetics containing the sequence proline-aspartic-threonine/serine-arginine (PDT/SR). Subsequent studies against lectins and antibodies have allowed to determine the ability of these glycopeptidomimetics to emulate the immunogenic properties of the biorecognition domain of the MUC1 (O-glycoprotein expressed in 90% of breast tumors). The synthesis of new modified derivatives of this protein incorporating different sp2-iminosugars that are recognized by antibodies and further improve their affinity, would provide a useful tool for the diagnosis of cancer in its earliest stages and even allow the rational design of vaccines.

Regarding lysosomal storage diseases, the second main objective of the project, we have focused on the synthesis of selective inhibitors of beta-glucosidase and beta-hexosaminidase A enzymes, criterion to identify pharmacological chaperone candidates for Gaucher disease and Tay-Sachs disease, respectively. Both diseases are known as lysosomal storage disorders, group of inborn errors of metabolism that affect the correct functioning of one of the lysosomal enzymes provoking progressive accumulation of the corresponding substrates in various organs and tissues causing various clinical manifestations, many of them progressive and irreversible. Thus, with the aim to get results against these fatal diseases, a collection of amphiphilic glycomimetics with sp2-iminosugar structure bearing a polyfluorinated chain of different length has been synthesized. These compounds have provided interesting results against Gaucher disease in patient fibroblasts. On the other hand, the access to new specific inhibitors of the enzyme beta-hexosaminidase A with 2-acetamido-2-deoxy-sp2-iminosugar structure, has allowed the identification of new pharmacological chaperones in fibroblasts from patients suffering from Tay-Sachs disease.

All in all, the development of the objectives planned in this project aims to achieve solutions to priority problems of public health so that the new knowledge acquired after its development provides real progress in the quality of life of patients, early diagnosis of cancer, design of vaccines, more potent and less toxic drugs, less expensive treatments, etc ...