Synthesis of Hsp90 inhibitor dimers as potential antitumor agents.

Structure-based drug design was used to systematically synthesize PU3-dimers. The cytotoxicity of PU3 dimers 6 against breast cancer cell lines was evaluated, and their potency increased as the length of the bridging linker increased. Among the compounds tested, 6e with a C-20 linker was the most potent and exhibited a 20- to 30-fold increase in activity compared with that of the parent compound 5. Western blot analyses of the cell lysates treated with 6c revealed that 6c resulted in the concentration-dependent degradation of the Hsp90 client protein Her2, which is consistent with other Hsp90 inhibitors.