IPI-504 (Retaspimycin hydrochloride)

Retaspimycin hydrochloride (also known as IPI-504), a hydroquinone hydrochloride salt derivative of 17-AAG, is a novel, potent and selective inhibitor of Hsp90 that binds at the N-terminal ATP/ADP-binding site of Hsp90. Once in the systemic circulation, IPI-504 is deprotonated and converted into the free base IPI-504 which is subsequently oxidized to 17-AAG.