ML-243 is a selective inhibitor of cancer stem cells. Displays 32-fold selective inhibition of a breast cancer stem cell-like cell line (EC₅₀ = 2.0 µM) over a control (mammary epithelial) cell line (EC₅₀ = 64 µM). It weakly antagonizes the adenosine A2A receptor (IC₅₀ = 10 µM) and has no effect on 68 other targets commonly used in drug discovery for lead profiling.