Fig. 4. Structure-based design of molecular glue.

a Flowchart of our structure-based design strategy of anagrelide analogs. b Focused view of the binding mode of anagrelide, where the favorable hydrophobic interactions are formed between the 7-chlorine atom in anagrelide and PDE3A-SLFN12 interfacial residues (L910, L554, I557, and I558). c Docking mode of compound A10, with the hydrophilic pyridyl substitute interacting unfavorably with the hydrophobic interfacial residues. d Docking mode of compound A4, with favorable hydrophobic interactions forming between the phenyl substitute with the interfacial residues. e Docking mode of compound A6, the p-tolyl group forms the most favorable hydrophobic contacts with the interfacial residues. f Modeled binding mode of compound A16, the negatively charged carboxyl group is not complementary with the hydrophobic interfacial residues. In b−f, SLFN12 and PDE3A were shown as red and sandy brown ribbons, respectively. The anagrelide and its analogs were represented by the ball stick. The red dashed line indicated hydrogen bonds. HeLa cells were treated with the indicated stimuli for 36 h, cell viability was determined by measuring ATP levels (n = 3, examined in three independent experiments), and IC₅₀ values were calculated using GraphPad Prism. The data are represented as the mean ± SD of triplicate wells. g Summary of the structure-activity relationship of the representative anagrelide analogs.