Flutamide is an antiandrogen drug, with its active metablolite binding at androgen receptor with Ki values of 55 nM, and primarily used to treat prostate cancer.Target: androgen receptor in vitro: Flutamide (Eulexin) is an antiandrogen drug. Flutamide-OH, the active metabolite of flutamide, directly binds at rat anterior pituitary androgen receptor with Ki values of 55 nM [1]. lutamide does not affect the proliferation of an androgen-sensitive clone of the mouse mammary carcinoma Shionogi SC-l 15 cells in culture, shows only antiandrogenic effect, but not androgenic effect [2]. Flutamide provides treatment for prostate cancer when used along with leuprolide [3].in vivo: Flutamide causes a markedly reduction in rat ventral prostate weight from 319 mg to 245 mg. A combination of flutamide and LHRH agonist induces an additive effect with a decrease in prostate weight to 101 mg, and an marked drop in prostatic ODC activity [4].

References:
[1]. Simard J, et al. Characteristics of interaction of the antiandrogen flutamide with the androgen receptor in various target tissues. Mol Cell Endocrinol. 1986 Mar;44(3):261-70.
[2]. Luthy IA, et al. Androgenic activity of synthetic progestins and spironolactone in androgen-sensitive mouse mammary carcinoma (Shionogi) cells in culture. J Steroid Biochem. 1988 Nov;31(5):845-52.
[3]. Crawford ED, et al. A controlled trial of leuprolide with and without flutamide in prostatic carcinoma. N Engl J Med. 1989 Aug 17;321(7):419-24.
[4]. Marchetti B, et al. Characteristics of flutamide action on prostatic and testicular functions in the rat. J Steroid Biochem. 1988 Jun;29(6):691-8.