In vitro activity: Elesclomol significantly induces the expression of heat shock stress response genes and metallothionein genes, a signature transcription profile indicative of oxidative stress in Hs294T cells. Elesclomol (100 nM) rapidly induces Hsp70 RNA levels with a 4.8-fold increase at 1 hour and a 160-fold increase at 6 hours in Ramos Burkitt's lymphoma B cells in consistent with the intracellular ROS content which increases by 20% as early as 0.5 hour and 385% at 6 hours, and the induction of Hsp70 can be blocked by antioxidants N-acetylcysteine (NAC) and Tiron pretreatment. Elesclomol increases the number of early and late apoptotic cells with 3.7- and 11-fold through the induction of oxidative stress, which can be completely blocked by NAC, while having little effect on normal cells. Elesclomol significantly inhibits the cell viability of SK-MEL-5, MCF-7, and HL-60 with IC50 of 110 nM, 24 nM and 9 nM, respectively. Elesclomol induces copper-dependent ROS generation and cytoxicity in yeast. Instead of working through a specific cellular protein target, Elesclomol interacts with the electron transport chain (ETC), a biologically coherent set of processes occurring in the mitochondrion, to generate high levels of ROS within the organelle and consequently cell death.

Cell Assay: Cells are treated with various concentrations of Elesclomol for 18 or 24 hours. The level of intracellular ROS is monitored using the DCFDA probe, which emits a green fluorescence on oxidation. Cell death is determined by flow cytometry of cells double stained with Annexin V/FITC and propidium iodide (PI) using a Vybrant Apoptosis assay kit.

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