Action of a novel nonsteroidal antiandrogen, AA560

Effects of antiandrogens on growth of androgen-dependent mouse mammary tumor (Shionogi carcinoma 115) in vivo and in vitro

Binding affinities of modified steroidal anthrasteroids, 3 beta-hydroxy-3a beta,6-dimethyl-2,3,3a,4,5,8,9,10,10a beta,11,11a beta, 11b alpha-dodecahydro-1H-cyclopenta[a]anthracene-8-one (1) and 3a beta,6-dimethyl-2,3,3a,4,5,8,9,10,10a beta,11,11a beta,11b alpha-dodecahydro-1H-cyclopenta[a]anthracene-3,8-dione (2), the steroid oxendolone and the nonsteroid AA560, for the androgen receptor (AR) of Shionogi carcinoma 115 (SC115) and their effects on the growth of SC115 were investigated in vivo and in vitro. The inhibitory effects of these compounds on testosterone 5 alpha-reductase of SC115 tissues were also measured. The relative binding affinities of these compounds were 3.17-0.03% of that of dihydrotestosterone, and their rank order was (1) greater than AA560 greater than oxendolone much greater than (2). In the presence of 10(-9) M testosterone, anthrasteroids and AA560 inhibited the growth of SC115 cells at 10(-7) M in a serum-free medium, but oxendolone did not. In the absence of testosterone, (1), (2) and oxendolone promoted cell growth at 10(-6), 10(-7) and 10(-7) M, respectively. However, AA560 nearly completely blocked cell growth at 10(-5) M. At a 2 mg daily dose for 13 days, (1) and AA560 powerfully inhibited tumor growth in castrated DS mice treated with testosterone propionate but oxendolone had almost no effect. Anthrasteroids and oxendolone showed weak but significant agonistic activity in vivo. Anthrasteroids markedly inhibited 5 alpha-reductase activity of SC115, oxendolone weakly and AA560 not at all. The remarkable antiandrogenic activities of (1) and AA560 may partially result from their higher affinities for the AR of SC115 but other yet unknown mechanisms may also contribute to these activities.

Effect of drug-vinyl copolymer delivery composites on the rat prostate

A radiation polymerized drug-vinyl copolymer delivery composite (0.8 mm in diameter, 3 mm long) was inserted into the right-lobe ventral prostate (I), into the right testis (II), and subcutaneously (III) into the back of male Wistar rats. The implantation was carried out over a period of 12 weeks maximum. From the relationship between the site of surgical insertion of the implant and the physiologic response (as measured by the decrease in the weight of the prostatic organs, e.g., ventral prostates, dorsolateral prostates, and seminal vesicles), it was found that in an AA560-containing composite (36 micrograms daily), the physiologic response is increased in order of (III) greater than (II) greater than (I). The same tendency was observed in the Estracyt-containing composite system (15 micrograms daily). The difference in the physiologic response owing to the site of surgical insertion of the implant was not observed in an E2-17 beta-containing composite (6 micrograms daily), although this composite showed the strongest physiologic response. No physiologic response in rats with CMA-containing composite (28 micrograms daily) was noted.

Mechanism of retention of estramustine in the rat prostate and results of a clinical trial of Estracyt in Japan

To clarify the mechanism of action of Estracyt, we performed experiments using 3H-estramustine of high specific activity. 3H-Radioactivity accumulated selectively in the ventral prostate of castrated male rats after the administration of 3H-estramustine. Estramustine and its metabolites were retained in the ventral prostate for long time periods. The uptake of 3H-radioactivity was almost totally localized in the cytosol fraction, but not in a purified receptor fraction. The apparent equilibrium dissociation constant of the estramustine binding protein was 18.9 nM, and the apparent equilibrium Bmax value was 0.76 nmoles/mg of cytosol protein. In addition, we wish to report in this paper the results of clinical trials of Estracyt studied by a cooperative research group in Japan from 1977 to 1979. It was concluded that Estracyt was effective in 89% of previously untreated prostatic cancer patients and in 38% of reactivated cancer patients.