Sialylation at the non-reducing end of glycoconjugates is involved in lots of important physiological and pathological processes. Especially cancer cells express high density of sialic acids known as hypersialylation that contributes to cancer cell progression and metastasis. Sialyltransferase is the glycosyltransferase in charge of sialylation of glycoconjugates. Effective sialyltransferase inhibitors could be not only of medicinal interests, especially in the therapy of cancer diseases, but also biological probes for studying fuctions of sialylation in glycobiology. Here we review recent progress of design and discovery of sialyltransferase inhibitors. The major content is about the design of different types of inhibitors and their structure-activity relationship. The current challenges and development trends are also proposed.

Contents
1 Introduction
2 Relationship between sialic acids and cancers
3 Design and discovery of sialyltransferase inhibitors
3.1 Donor-analog inhibitors
3.2 Acceptor-analog inhibitors
3.3 Bisubstrate-analog inhibitors
3.4 Transition-state-analog of the sialyl donor inhibitors
3.5 Other types of inhibitors
4 Conclusion