E-selectin antagonists: fragment-based drug discovery and lead optimization by NMR and BIAcore

The inflammatory response consists of a well-defined and regulated multi-step cascade leading to extravasation of leukocytes from the blood to sites of inflammation. The transmigration of leukocytes is initiated by their interaction with the endothelium, a process regulated by selectins, a family of cell adhesion molecules. This Ph.D. thesis is focused on E-selectin - a C-type type (Ca2+-dependent) lectin.
Excessive recruitment of leukocytes, as observed in inflammatory diseases (e.g. asthma or arthritis), is problematic because the inflammatory response itself becomes harmful. Consequently, the modulation of leukocyte recruitment by interfering with cell tethering is of therapeutical interest.
Sialyl LewisX (sLex) is the minimal carbohydrate epitope of physiological ligands recognized by E-selectin. This moderate binder (in the millimolar range) has served as a lead structure for the design of more potent E-selectin antagonists. This optimization process was supported by NMR and SPR, leading to the first generation of low micromolar antagonists of E-selectin. These contributions are presented in this thesis. By ligand-based NMR experiments a better understanding of the physical basis of the interaction was obtained.
In a next step, fragment-based methods that have emerged as a new strategy in drug discovery were successfully applied to the lead optimization of E-selectin antagonists. The improved affinities as well as the increased residence time impressively demonstrate the potential of the applied fragment-based approach.