Chronic progesterone antagonist-estradiol therapy suppresses breakthrough bleeding and endometrial proliferation in a menopausal macaque model

The translational efficacy of a nonsteroidal progesterone receptor antagonist, 4-[3-cyclopropyl-1-(mesylmethyl)-5-methyl-1H-pyrazol-4-yl]oxy,-2,6-dimethylbenzonitrile (PF-02413873), on endometrial growth in macaque and human

There is considerable ongoing investment in the research and development of selective progesterone receptor (PR) modulators for the treatment of gynecological conditions such as endometriosis. Here, we provide the first report on the clinical evaluation of a nonsteroidal progesterone receptor antagonist 4-[3-cyclopropyl-1-(mesylmethyl)-5-methyl-1H-pyrazol-4-yl]oxy,-2,6-dimethylbenzonitrile (PF-02413873) in healthy female subjects. In in vitro assays, PF-02413873 behaved as a selective and fully competitive PR antagonist, blocking progesterone binding and PR nuclear translocation. The pharmacological mode of action of PF-02413873 seems to differ from the founding member of the class of steroidal PR antagonists, 11β-4-dimethylaminophenyl-17β-hydroxy-17α-propinyl-4,9-estradiene-3-one (RU-486; mifepristone). Exposure-effect data from studies in the cynomolgus macaque, however, demonstrated that PF-02413873 reduced endometrial functionalis thickness to a comparable degree to RU-486 and this effect was accompanied by a decrease in proliferation rate (as measured by bromodeoxyuridine incorporation) for both RU-486 and high-dose PF-02413873. These data were used to underwrite a clinical assessment of PF-02413873 in a randomized, double-blinded, third-party open, placebo-controlled, dose-escalation study in healthy female volunteers with dosing for 14 days. PF-02413873 blocked the follicular phase increase in endometrial thickness, the midcycle lutenizing hormone surge, and elevation in estradiol in a dose-dependent fashion compared with placebo. This is the first report of translational efficacy data with a nonsteroidal PR antagonist in cynomolgus macaque and human subjects.

Family planning: today and in the future

This review covers the state of contraceptive development noting new entries in the clinic (mainly steroidal and different delivery methods) and novel leads for nonsteroidal female- and male-methods in the pipeline. The time taken to market and the absence of partnerships with industry are stressed as major factors for the slow progress in their development.

2-Amino-9-aryl-3-cyano-4-methyl-7-oxo-6,7,8,9-tetrahydropyrido[2',3':4,5]thieno[2,3-b]pyridine derivatives as selective progesterone receptor agonists

High throughput screening of the corporate compound collection led to the identification of a novel series of 2-amino-9-aryl-3-cyano-4-methyl-7-oxo-6,7,8,9-tetrahydropyrido[2',3':4,5]thieno[2,3-b]pyridine derivatives as selective PR agonists. Initial SAR exploration leading to potent and selective agonists 9 and 11, X-ray crystal structure of 9 bound to PR-LBD and preliminary developability data are described.

Discovery of orally active, pyrrolidinone-based progesterone receptor partial agonists

We have designed and synthesized a novel series of pyrrolidinones as progesterone receptor partial agonists. Compounds from this series had improved AR selectivity, rat pharmacokinetic properties, and in vivo potency compared to the lead compound. In addition, these compounds had improved selectivity against hERG channel inhibition.

Antiprogestin-releasing intrauterine devices: a novel approach to endometrial contraception

Intrauterine devices (IUDs) that release progestins are highly effective contraceptives, but they induce breakthrough bleeding that some women find unacceptable. Because progesterone (P) antagonists [antiprogestins (APs)] are known to suppress the endometrium, induce amenorrhea and inhibit fertility, AP-releasing IUDs (AP-IUDs) may provide an effective contraceptive that also controls endometrial bleeding. Here, we assessed the effects of empty (blank) vs. AP-IUDs (ZK 230 211) on bleeding patterns and endometrial growth in ovariectomized, artificially cycled macaques. The AP-IUDs (but not the blank controls) induced extended, frank menstruation when inserted during the late luteal phase, an indication of local AP action. Over time, endometrial glandular and arterial proliferation were inhibited, steroid receptors were elevated, spiral arteries showed degenerative changes, P withdrawal bleeding was prevented, and estradiol (E(2))-dependent proliferation was suppressed by the AP-IUDs. In sum, AP-IUDs suppressed the effects of P on endometrial progestational development and blocked the effects of E(2) on endometrial proliferation, as previously shown for systemic treatment with APs. Therefore, AP IUDs may provide novel contraceptive devices with minimal breakthrough bleeding.