Antibiotics having intrinsic anti-mitochondrial properties may be chemically modified to target the antibiotics to mitochondria, and the resulting “antimitoscins” may have enhanced anti-cancer properties, among other advantageous properties. Also described are methods for identifying antimitoscins, methods of using antimitoscins to target cancer stem cells, and pharmaceutical compositions for treating cancer containing one or more antimitoscins as the active ingredient. Specific antimitoscins compounds and groups of antimitoscins are also disclosed.