Nonsteroidal antiestrogens and partial estrogens with prostatic tumor inhibiting activity.

Antiestrogens and partial estrogens of the stilbene (1 and 4), triphenylbutene (2) and diphenylethane (3) series were tested for their potential prostatic tumor inhibiting activity. Compounds 1 and 2 exerted a strong inhibitory activity on prostate and seminal vesicle weight of intact rats and mice, whereas the strong antiestrogen 3 and compound 4 had no or only a slight effect. The tumor inhibiting activity of 1 and 2 on the hormone-dependent R 3327 Dunning prostatic carcinoma of the rat was strong and comparable to that of castration or administration of the potent estrogen DES. Compounds 1-4 had no direct antiandrogenic effect in castrated, testosterone-substituted rats and mice, and no affinity for the androgen or progesterone receptor. To the estrogen receptor from prostatic tumor cytosol, however, 1-4 had good receptor affinities. As the partial antiestrogen 1 and the partial estrogen 2 have much lower estrogenic properties than DES, but still have strong prostatic tumor inhibiting properties, they may offer a suitable alternative to conventional therapy of prostate carcinoma because of their possibly low estrogenic side effects.