A benzoquinone ansamycin antibiotic that acts as a cell-permeable inhibitor of non-receptor tyrosine kinases and Hsp90; inhibits Bcr-Abl with an IC50 value of 5 μM, a concentration that also effectively blocks Src, Yes, Fps, Ros, and ErbB; binds Hsp90 and destabilizes client proteins, including Src, Bcr-Abl, and ErbB2