This invention relates to anti - cancer compounds and to methods for treating or preventing cancer . In one aspect the invention concerns mitochondrially delivered pro - oxidant anti - cancer compounds that generate reactive oxygen spe cies and induce apoptosis of cancerous cells . The delivery moiety can be a lipophilic cation and the pro - oxidant moiety can be a pro - oxidant vitamin E analogue , such as a - tocoph eryl succinate , a - tocopheryl maleate , a - tocopheryl maleyl amide , or 2 , 5 , 7 , 8 - tetramethyl - 2R - ( 4R , 8R , 12 - trimethyltride cyl ) - chroman - 6 - yloxyacetic acid ( a - tocopheryloxyacetic acid ) .