Disclosed are a class of compounds for treating or preventing breast cancer, in particular 2-phenyl benzoselenazole compounds, and a pharmaceutically acceptable salt thereof and an easily hydrolysable prodrug thereof. Further disclosed are a pharmaceutical composition containing these compounds and the use of such compounds for for treating or preventing breast cancer in mammals. The compounds of the present invention can effectively inhibit or reduce the growth or proliferation of mammalian breast cancer cells, and at the same time, such compounds do not inhibit the growth of partial test cells, apart from breast cancer cells in mammals, and have a good selectivity. Such compounds show a more obvious medicinal effect, and have high selectivivity, low toxicity and few side effects.
