Antiandrogenic steroidal sulfonyl heterocycles. Utility of electrostatic complementarity in defining bioisosteric sulfonyl heterocycles.

Complementarity of electrostatic potential surface maps was utilized in defining bioisosteric steroidal androgen receptor antagonists. Semiempirical and ab initio level calculations performed on a series of methanesulfonyl heterocycles indicated the requirement for a partial negative charge at the heteroatom attached to C-3 of the steroid nucleus to attain androgen receptor affinity. Synthesis and testing of six heterocycle A-ring-fused dihydroethisterone derivatives support this hypothesis, and we have identified two new androgen receptor antagonists of this class.

The effect of the steroidal androgen receptor antagonist, Win 49,596, on the prostate and testis of beagle dogs.

The effect of the steroidal androgen receptor antagonist Win 49,596 on the prostate and testis was studied in beagle dogs and was compared to the effects of the nonsteroidal androgen receptor antagonist ICI 176,334 and the steroidal 5 alpha-reductase inhibitor MK-906. Win 49,596 was shown to bind to the androgen receptor from normal canine prostate with a Ki of 2.2 microM. After 16 weeks of treatment, prostate size, as estimated by transrectal ultrasonography, was unchanged in intact controls and was 26% of the initial size in castrate controls. Oral doses of Win 49,596 from 0.625-40 mg/kg.day for 16 weeks caused dose-dependent prostatic regression and a dose-related increase in both the incidence and severity of glandular atrophy of the prostate. Prostatic secretory function was also inhibited by Win 49,596 treatment. The effects of Win 49,596 at 40 mg/kg.day on prostatic weight, total DNA, histomorphology, and secretory function were similar to those of castration, while the effects of Win 49,596 at 10 mg/kg.day were similar to those of ICI 176,334 at 0.25 mg/kg.day and MK-906 at 1.0 mg/kg.day. No effects on testicular weight, daily sperm production, or spermatogenesis were observed; however, mild Leydig cell hyperplasia was observed in two dogs treated with 40 mg/kg.day Win 49,596. In addition, at 10 and 40 mg/kg.day Win 49,596, moderate but variable increases in serum testosterone levels were observed. In summary, Win 49,596 caused regression of the hypertrophic canine prostate without effects on spermatogenesis and/or sexual function, supporting its possible use in the treatment of human benign prostatic hypertrophy/hyperplasia.

Effect of the steroidal androgen receptor antagonist Win 49,596 on steroid-induced benign prostatic hyperplasia in the castrate beagle dog.

The effects of the steroidal androgen receptor antagonist Win 49,596 on steroid-induced prostatic growth, histomorphology, and secretory function were studied in the castrate male beagle dog. At oral doses ranging from 0.625 to 40 mg/kg/day for 12 weeks, Win 49,596 inhibited prostatic growth in terms of both weight and total DNA in a dose-dependent manner. In addition, both the incidence and severity of diffuse glandular hyperplasia/hypertrophy were dose-dependently inhibited by Win 49,596, resulting in diffuse glandular atrophy. Prostatic secretory function was also inhibited by Win 49,596 treatment. The effects of Win 49,596 at a dosage of 40 mg/kg/day were similar to that observed for the nonsteroidal androgen receptor antagonist flutamide at 10 mg/kg/day. Oral administration of Win 49,596 to castrate dogs at a dosage of 40 mg/kg/day for 12 weeks failed to produce any evidence of agonist activity. These results demonstrate that Win 49,596 prevented the experimental induction of benign prostatic hyperplasia in dogs and suggest that on further evaluation this compound may be efficacious in the treatment of the human disease.

Studies on the mechanism of action of Win 49596: a steroidal androgen receptor antagonist.

Win 49596 is an orally active antiandrogen in the rat. This report describes a series of in vitro and in vivo studies which were performed to characterize the mechanism of action of this compound. In vitro competition and Lineweaver-Burk analyses indicate that Win 49596 binds competitively to the rat ventral prostate androgen receptor with a Ki of 2.2 +/- 0.4 microM. Similar to other androgen antagonists, the relative binding affinity (RBA) of Win 49596 was greater after 1 h of incubation with androgen receptor than after an 18 h incubation (RBA of 2.2 versus 0.05, respectively). Win 49596 did not bind to rat cytosolic uterine estrogen or progesterone receptors or thymus glucocorticoid receptors. Furthermore, Win 49596 did not inhibit rat ventral prostate 5 alpha-reductase or 3 alpha-oxidoreductase, rat adrenal 3 beta-hydroxysteroid dehydrogenase or human placental aromatase activity in vitro at concentrations as high as 10 microM. A series of in vivo studies demonstrated that Win 49596 inhibited the uptake of [3H]testosterone as well as testosterone-induced nuclear accumulation of androgen receptor in the rat ventral prostate. Collectively, these results support direct androgen receptor antagonism as the mechanism for the antiandrogenic effects of Win 49596.

Endocrine profile of Win 49596 in the rat: a novel androgen receptor antagonist.

Win 49596 is a new orally active, steroidal androgen receptor antagonist. Win 49596 inhibited ventral prostate, seminal vesicle and levator ani weight gain in either 5 alpha-dihydrotestosterone (DHT) or testosterone propionate-treated castrated, immature male rats. In intact, adult male rats, Win 49596 significantly inhibited weight gain by the ventral prostate, dorsal lateral prostate and seminal vesicles, but not the testes at doses as low as 50 mg/kg/day x 14 p.o. However, daily oral administration of equivalent antiandrogenic doses of either Win 49596, ICI 176,334, or flutamide for 14 days to mature, intact male rats resulted in elevations of circulating testosterone of approximately 3-, 2-, and 10-fold, respectively. At doses as high as 400 mg/kg p.o., Win 49596 did not have androgenic, progestational, estrogenic or antiestrogenic activity in rat or rabbit models. However, in the Clauberg assay, Win 49596 did have weak antiprogestational activity at doses of 25-400 mg/kg/day p.o. These data indicate that Win 49596 is a peripherally selective antiandrogen that has minimal effects on circulating testosterone levels and is devoid of hormone agonist activity. Thus, Win 49596 may be useful for the treatment of androgen dependent conditions such as benign prostatic hyperplasia and prostatic cancer.

Effect of epostane, ZK 98299, and ZK 98734 on the interruption of pregnancy in the rat.

The objective of these studies was to determine whether treatment of 10-day pregnant rats with a combination of epostane (a progesterone biosynthesis inhibitor) and either ZK 98299 or ZK 98734 (progesterone receptor antagonists) would result in additive or synergistic effects on the interruption of pregnancy. When these compounds were tested individually, the order of potency in interrupting pregnancy was ZK 98734 greater than ZK 98299 greater than epostane (50% effective doses 1.3, 4.0, and 35 mg/kg, respectively). Epostane and ZK 98299 were then tested in combination. When epostane was given either 4 h prior to or concurrently with ZK 98299, the combined drug treatment resulted in a significant additive increase in interceptive activity compared to when ZK 98299 was administered alone. In vitro binding studies showed that ZK 98299 and ZK 98734 bound to the rat uterine progesterone receptor in vitro with approximately equal affinity. ZK 98734 bound to the rat thymus glucocorticoid receptor and to the rat ventral prostate androgen receptor with a greater affinity than ZK 98299. The affinity of ZK 98299 for the rat uterine estrogen receptor was weak while the binding of ZK 98734 was not detectable. Thus, the in vitro receptor binding profiles observed were consistent with the known progesterone and glucocorticoid antagonist activities of ZK 98299 and ZK 98734. Overall these findings show that the interceptive activity of epostane and ZK 98299, agents that exert their interceptive activity via different molecular mechanisms, is additive in the 10-day pregnant rat.

Dose-dependent hormonal induction of benign prostatic hyperplasia (BPH) in castrated dogs.

A model for the dose-dependent hormonal induction of benign prostatic hyperplasia (BPH) in castrated dogs has been established using subcutaneously implanted Silastic capsules containing 5 alpha-androstane-3 alpha, 17 beta-diol (3 alpha-diol) and estradiol-17 beta. In vivo release rates per capsule approximated 122.0 +/- 4.2 micrograms 3 alpha-diol and 22.7 +/- 0.8 micrograms estradiol per day based on in vitro studies and resulted in dose-dependent increases in serum 3 alpha-diol and dihydrotestosterone concentrations. The implantation of castrated dogs with either 10 or 20 Silastic capsules containing 3 alpha-diol and one capsule containing estradiol or the intramuscular injection of 3 alpha-diol (75 mg/week) and estradiol (0.75 mg/week) for 99 days significantly increased (P less than .01) prostatic weights and total prostatic DNA over intact controls. These treatments also resulted in a histomorphological pattern similar to that observed in dogs with the glandular form of spontaneous BPH. In addition, normal prostatic secretory function as determined by semen volume was maintained in these dogs. Although subcutaneous implantation of five Silastic capsules containing 3 alpha-diol and one capsule containing estradiol into castrated dogs resulted in prostatic weights and total prostatic DNA that were similar (P less than .10) to intact controls, these prostates were characterized histomorphologically by glandular atrophy and squamous metaplasia. Furthermore, prostatic secretory function was decreased (P less than .05) in these animals compared with intact controls at 3 months of treatment. This study has led to the development of a model of steroid-induced BPH that will facilitate the evaluation of competitive androgen-receptor antagonists in the dog.

Transrectal ultrasonography as a method to monitor canine prostatic size in situ: measurements following endocrine manipulation and ejaculation.

Transrectal ultrasonography was utilized to estimate canine prostatic size in situ following various experimental manipulations. By the use of dogs (n = 24) of various endocrine states, whose true prostatic weight varied from 2.28 to 73.25 g, a highly significant correlation (r = 0.99; P less than 0.0001) was obtained between actual prostate weight determined gravimetrically and that estimated by ultrasound. The relationship between these two parameters was described by the regression equation: estimated prostatic weight (g) = 1.11 x gravimetric weight (g) - 0.12. In addition, prostatic weight as estimated by ultrasound was comparable (P less than 0.10) to that estimated by direct caliper measurement. The coefficient of variation associated with repeated ultrasound measurements averaged 8.88 +/- 2.31% (mean +/- SD; n = 5). Ejaculation induced by either digital massage or pilocarpine administration (0.7 mg/kg, i.v.) had no effect on prostatic weight as estimated by ultrasound. These results demonstrate that transrectal ultrasonography can accurately estimate and detect differences in prostate size owing to various experimental manipulations without the need for surgical intervention.

Kinetic parameters of 5 alpha-reductase activity in stroma and epithelium of normal, hyperplastic, and carcinomatous human prostates.

To study the influence of 5 alpha-reductase on the concentration of dihydrotestosterone in prostatic tissue, we measured the activity of this enzyme in stroma and epithelium from 15 normal, 50 hyperplastic, and 20 carcinomatous prostates. Maximum velocity (Vmax) and Km parameters based on the Lineweaver-Burk and Eadie-Hofstee transformations of the Michaelis-Menten equation were related to the stromal and epithelial concentrations of dihydrotestosterone. On the basis of relative Vmax values, there was 6-15 times more 5 alpha-reductase activity in stroma than in epithelium regardless of the histology of the prostate. Stromal enzyme activity also was unique in having a 2- to 5-fold larger mean Km value and greater resistance to competitive and noncompetitive inhibition. Despite the enrichment of 5 alpha-reductase activity in stroma, the dihydrotestosterone concentrations in the stromal and epithelial fractions were very similar. In addition, similar concentrations were found in the stromal fractions of hyperplastic and carcinomatous tissues, notwithstanding a 4-fold difference in the mean Vmax values. This anomaly occurred in association with a large disparity in mean Km values, i.e. 68.3 +/- 1.6 (+/- SE) nmol/L in hyperplasia vs. 23.0 +/- 2.9 nmol/L in carcinoma. The dissociation between parameters of 5 alpha-reductase activity and tissue dihydrotestosterone concentrations was apparent to some extent in benign prostatic hyperplasia, in which the lowest stromal androgen concentrations were found in prostates with the largest Vmax and Km values; also, a rise in stromal Km was almost invariably associated with a proportional increase in Vmax (correlation coefficient = 0.95). These data strongly suggest that the stromal and epithelial forms of 5 alpha-reductase are separate isoenzymes, and that the excess of 5 alpha-reductase in stroma does not promote accumulation of an abnormal amount of dihydrotestosterone. They also imply that both the augmentation of 5 alpha-reductase activity in hyperplastic stroma and the condition of benign hyperplasia of the prostate are mutual consequences of a primary increase in Km.

Kinetic analysis of 5 alpha-reductase isoenzymes in benign prostatic hyperplasia (BPH).

Kinetic parameters (KM and Vmax) of the 5 alpha-reductase activities in homogenates of stroma and epithelium, isolated from BPH tissue, were determined using both testosterone and progesterone as substrate. The mean KM values for stromal 5 alpha-reductase, at 67.9 nM and 27.7 nM for testosterone and progesterone respectively, were 3-4-fold higher than the comparable KM estimates for the epithelial enzyme. The KM estimates for the epithelial 5 alpha-reductase showed little variation whereas those measured in the stromal homogenates could be subgrouped at less than 50 nM and greater than 100 nM. The mean Vmax for the stromal 5 alpha-reductase was approximately 235 pmol/30 min/mg protein irrespective of the substrate used; a value 10-fold higher than the Vmax of the epithelial 5 alpha-reductase. Preliminary experiments with inhibitors of 5 alpha-reductase demonstrated that the stromal and epithelial enzymes differed in their relative sensitivity to these compounds. Three major conclusions can be drawn from these results: first, that progesterone is a better substrate for prostatic 5 alpha-reductase than testosterone; second, that BPH tissue has at least two isoenzymes of 5 alpha-reductase--one in the epithelium and one (or more) in the stroma; and third, in hyperplastic prostates, most of the 5 alpha-reductase molecules are located in the stroma.

Effects of novel acetylenic and allenic steroids on the rat prostate.

Novel acetylenic and allenic steroid analogs previously have been synthesized in this laboratory and were shown to be potent irreversible inhibitors of delta5-3-ketosteroid isomerase from P. Testosteroni. This bacterial enzyme catalyzes the conversion of delta5-3-ketosteroids to the corresponding delta4-3-ketosteroids. These isomerizations are key steps in the mammalian biosynthesis of steroid hormones, and it was hoped that the acetylenic and allenic steroid analogs migh inhibit androgen biosynthesis. We have now shown that these compounds cause a significant and dose-dependent decrease in the wet weight of both ventral and dorsal lateral prostate in the mature male rat.