We have highlighted throughout this thesis that fragment-based drug design (FBDD) and structure-based drug design (SBDD) still constitute a number of challenges such as the risk associated with de novo SBDD and are time-consuming as they involve synthesis and validation of the binding mode of each derivative in the fragment/hit-optimization cycle. To overcome these hurdles, we combined FBDD or de novo SBDD projects with dynamic combinatorial chemistry (DCC) or protein-templated click chemistry (PTCC) to render the identification/optimization of hits/leads more efficient, using the aspartic protease endothiapepsin as a model system. The main achievements described in this thesis are: 1) the development of a powerful technique that combines d...