An Hsp90 inhibitor (IC50 = 3.8 nM for Hsp90α); inhibits the growth of OPM-2/GFP, KMS011, RPMI 8226, and NCI-H929 multiple myeloma cells (GI50s = 0.3, 0.34, 0.39, and 0.12 μM, respectively) and Raji, SR, and SC-1 non-Hodgkin's lymphoma cells (GI50s = 0.39, 0.098, and 0.33 μM, respectively); decreases expression of IGF-IRβ and c-RAF-1 and induces apoptosis in OPM-2/GFP and NCI-H929 cells; reduces IGF-IRβ, c-RAF-1, Cdk9, and phosphorylated ERK1/2 protein levels in tumor tissue and decreases tumor growth in an NCI-H929 mouse xenograft model at 100 mg/kg,