The present invention mainly aims to provide a drug for the prophylaxis or treatment of androgen-independent prostate cancer, which is highly useful as a pharmaceutical agent.The present invention provides a drug for the prophylaxis or treatment of androgen-independent prostate cancer, containing a steroid C17,20lyase inhibitor, particularly, a compound represented by the formula (I):wherein n is an integer of 1 to 3, and Ar is an aromatic ring optionally having substituent (s), or a salt thereof or a prodrug thereof.本發明之主要目的係提供預防或治療雄激素非依賴性前列腺癌之藥物，其在作為藥劑上非常有用。本發明提供預防或治療雄激素非依賴性前列腺癌之藥物，其含有類固醇C17,20分解酶抑制劑，尤其是式(1)所代表之化合物或其鹽或其前藥：式中，n為1至3之整數，且Ar為視需要具有取代基之芳族環。
