Development of novel steroid sulfatase inhibitors; II. TZS-8478 potently inhibits the growth of breast tumors in postmenopausal breast cancer model rats.

In postmenopausal breast cancer tissue, steroid sulfatase (STS) activity is high and much estrone sulfate also exists; these facts reveal that estrone sulfate may be involved in the growth of breast cancer as an estrogen source. Steroid sulfatase is an enzyme, which catalyzes hydrolysis from estrone sulfate to estrone, and the development of steroid sulfatase inhibitors is expected as novel therapeutic drugs for postmenopausal breast cancer. We have developed a novel compound 2',4'-dicyanobiphenyl-4-O-sulfamate (TZS-8478), which has potent steroid sulfatase-inhibitory activity and exhibits no estrogenicity in vitro and in vivo. To elucidate its usefulness as a therapeutic drug for postmenopausal breast cancer, we examined the breast cancer cell proliferation- and breast tumor growth-inhibitory activity of TZS-8478 in postmenopausal breast cancer model rats. TZS-8478 dose-dependently suppressed the estrone sulfate-stimulated proliferation of MCF-7 cells. Regarding nitrosomethylurea (NMU)-induced postmenopausal breast cancer models, furthermore, TZS-8478 (0.5 mg/kg per day) markedly inhibited the estrone sulfate-stimulated growth of breast tumors similarly to estrone sulfate-depletion. TZS-8478 completely inhibited steroid sulfatase activity in tumor, uterus and liver, and also markedly lowered plasma concentrations of estrone and estradiol. The above mentioned results suggested that TZS-8478 may be useful as a therapeutic drug for estrogen-dependent postmenopausal breast cancer.

Development of novel steroid sulfatase inhibitors. I. Synthesis and biological evaluation of biphenyl-4-O-sulfamates.

Compounds which interfere with steroid sulfatase (STS) are expected as important novel therapeutic drugs for postmenopausal breast tumor. Therefore, a number of strategies have been adopted to design and synthesize potent, nonestrogenic STS inhibitors. We chose biphenyl as a scaffold for STS inhibitors and synthesized some biphenyl-4-O-sulfamate derivatives (29-43). Their inhibitory activity on STS and estrogenicity were evaluated. Substitution of electron-withdrawing groups (e.g., cyano, nitro) at the 2'- or 4'-position of biphenyl-4-O-sulfamate remarkably increased STS-inhibitory activity. Especially, 2',4'-dicyanobiphenyl-4-O-sulfamate (35, TZS-8478) showed very potent STS-inhibitory activity in vitro. The administration of TZS-8478 (0.5 mg/kg per day, p.o., for 5 days) completely inhibited rat liver and uterine STS similarly to EMATE (1). Furthermore, TZS-8478 (10 mg/kg per day, p.o., for 5 days) had no stimulative effect on uterine growth in ovariectomized rats, and its desulfamoylated compound (20) was little bound to the human estrogen receptor alpha. The identification of a potent steroid sulfatase inhibitor without estrogenicity, such as TZS-8478, should be of considerable value in evaluating the potential of steroid sulfatase inhibition for breast tumor therapy.

Effects of the novel orally active antiestrogen TZE-5323 on experimental endometriosis.

Danazol and gonadotropin-releasing hormone agonists which are used as therapeutic drugs for endometriosis, develop adverse reactions in association with their long-term use. The efficacy of anti-estrogens for endometriosis, an estrogen-dependent disorder, has not been demonstrated. A novel, orally active anti-estrogen, TZE-5323 ((2-cyclohexy-6-hydroxybenzo[b]thien-3-yl)[4-[2-(1- piperidinyl)ethoxy]phenyl] methanone hydrochloride, CAS 150797-71-0; free salt formula) was developed. TZE-5323 showed strong affinity for human estrogen receptor alpha (hER alpha) and beta (hER beta), and dose-dependently inhibited estradiol-stimulated transcriptional activation via hER alpha and hER beta. Furthermore, TZE-5323 dose-dependently reduced estrogen-increased uterine weight in ovariectomized rats. Tamoxifen showed agonistic activity on hER alpha, while TZE-5323 did not show such activity. In the experimental endometriosis model in rats in which endometrial tissue is autotransplanted into the renal subcapsular space, TZE-5323 dose-dependently reduced the volume of the endometrial implant as did danazol and leuprorelin acetate. Furthermore, the long-term administration of TZE-5323 neither showed a decrease in bone mineral density nor did it affect serum estradiol concentrations in intact rats. Therefore, TZE-5323 suggested its potential as a novel therapeutic drug for endometriosis which is effective also in long-term use.

Pharmacokinetics and biliary excretion of osaterone acetate, a new steroidal antiandrogen, in dogs.

The pharmacokinetics and biliary excretion of osaterone acetate (17alpha-acetoxy-6-chloro-2-oxa-4,6-pregnadiene-3,20-dione; OA), a new steroidal antiandrogen, were investigated in intact dogs and biliary fistula dogs after bolus intravenous administration of (14)C-labeled drug. In intact dogs, OA exhibited a biexponential disposition with a very long half-life of 197.9 +/- 109.9 h. OA accounted for almost all the plasma radioactivity. The major route of excretion was in feces via the bile. One-third of the radioactivity in the bile was due to OA. The major biliary metabolite was identified as a glucuronide of 17alpha-acetoxy-6-chloro-21-hydroxy-2-oxa-4,6-pregnadiene-3,20-dione. A significant amount of biliary recycling occurs in dogs.