How the study of the biological activities of antiandrogens can be oriented towards the clinic.

Antiandrogens can be used in various androgen-dependent diseases. Depending upon the therapeutic indication, they can be administered systemically or topically. Systemic treatment with an antiandrogen will inhibit androgen action not only in the desired target site but also in all other target tissues; thus, it will block the androgen-dependent feedback regulating the secretion (hypothalamo-pituitary-testis axis) or the action (protein factors) of androgens. In contrast, topical treatment (acting through cutaneous receptors or local metabolism) should not produce systemic side effects especially in man. Pharmacological assays which can select antiandrogens irrespective of the mechanism measure changes in the final androgenic response, but they consume a great deal of time and test compound and bear little relation to therapeutic activity. Therefore, the biological strategy that we report here and which, at Roussel-Uclaf, has led to the selection of a systemic and a topical antiandrogen (RU 23908 and RU 38882) has consisted in successively performing: (1) in vitro assays which measure an effect at a specific level in the mechanism of antiandrogen action, e.g. interaction with the androgen receptor. Assessing interactions with other classes of steroid hormone receptor can be used to predict possible hormonal side-effects, (2) in vitro determinations of agonist or antagonist activity, e.g. in pituitary cells (LH response to LHRH) or mammary tumor cells (induction of androgen-dependent proteins), (3) in vivo antiandrogen assays after a single treatment (induction of mouse kidney proteins, rat prostatic binding protein) or after repeated treatment (inhibition of the growth of rat accessory glands or of hamster sebaceous glands), to determine the active dose of the compound and possibly the absence of systemic effects by the topical route, (4) assays in animal models designed to mimic a therapeutic context e.g. for prostate cancer: inhibition of the "flare-up" effect of LHRH-A or of the trophic effect of perfused adrenal androgens on rat prostate, antitumoral activity in experimental cancer models. For hyperseborrhoea and acne: histological and stereological analysis of rat skin biopsies to measure the volume density of the smooth endoplasmic reticulum vesicles of the differentiating cells of the sebaceous gland.