[Problem] An object of the present invention is to provide a novel anticancer drug which is useful for treating prostate cancer accompanying androgen receptor mutation [Means for Solution] The present inventors conducted thorough research on mutant androgen-related diseases for which the traditional anti-androgen drugs become ineffective. As a result, they found that the compound, which is an active ingredient of the pharmaceutical composition of the present invention, exhibits an inhibitory action against transcriptional activation in a human mutant androgen receptor (AR), and has an excellent antitumor action in a human prostate cancer-bearing mouse, thereby completing the present invention. Accordingly, the compound, which is an active ingredient of the pharmaceutical composition of the present invention, is useful for a series of androgen receptor-related diseases including prostate cancer.
