First Structure–Activity Relationship of 17β-Hydroxysteroid Dehydrogenase Type 14 Nonsteroidal Inhibitors and Crystal Structures in Complex with the Enzyme

17β-HSD14 belongs to the SDR family and oxidizes the hydroxyl group at position 17 of estradiol and 5-androstenediol using NAD⁺ as cofactor. The goal of this study was to identify and optimize 17β-HSD14 nonsteroidal inhibitors as well as to disclose their structure–activity relationship. In a first screen, a library of 17β-HSD1 and 17β-HSD2 inhibitors, selected with respect to scaffold diversity, was tested for 17β-HSD14 inhibition. The most interesting hit was taken as starting point for chemical modification applying a ligand-based approach. The designed compounds were synthesized and tested for 17β-HSD14 inhibitory activity. The two best inhibitors identified in this study have a very high affinity to the enzyme with a <i>K</i>_i equal to 7 nM. The strong affinity of these inhibitors to the enzyme active site could be explained by crystallographic structure analysis, which highlighted the role of an extended H-bonding network in the stabilization process. The selectivity of the most potent compounds with respect to 17β-HSD1 and 17β-HSD2 is also addressed