Regulation of female fertility and identification of future contraceptive targets.

Mammalian reproduction is a complex physiological process involving a tightly regulated hypothalamic-pituitary-gonadal axis and the integration of a diverse array of molecular signals. Oral contraceptives (OCs) were introduced over 40 years ago and have evolved over the years through the discovery of new estrogens and progestins, the development of progestin-only pills and the reduction of the estrogen content in combined OCs. Despite the developments that improved the safety profile of current OCs, adverse metabolic and vascular effects caused by the estrogen component and possible neoplastic effects of OCs remain and, thus, necessitate efforts to develop newer, possibly non-steroidal and non-hormonal, contraceptives. Recent advances in our understanding of ovarian endocrinology, coupled with molecular biology and transgenic technology, have enabled identification of several factors that are functionally critical in the regulation of female fertility. Progress in the area of female reproduction is showing great promise for identifying new contraceptive drug targets. In this article, the authors review the field of female contraception with emphasis on novel targets involved in reproductive function and identified through genomics and proteomics. In addition, the usefulness of these targets for contraception purposes will be discussed.

Identification and characterization of a selective, nonpeptide follicle-stimulating hormone receptor antagonist.

The glycoprotein hormones (LH, FSH, and TSH) are critical to the maintenance of physiological homeostasis and control of reproduction. However, despite an obvious utility for synthetic pharmacological agents, there are few reports of selective, nonpeptide agonists or antagonists to receptors for these hormones. We have identified and characterized a novel synthetic molecule capable of inhibiting the action of FSH. This compound, 7-[4-[Bis-(2-carbamoyl-ethyl)-amino]-6-chloro-(1,3,5)-triazin-2-ylamino)-4-hydroxy-3-(4-methoxy-phenylazo)-naphthalene]-2-sulfonic acid, sodium salt (compound 1), is a selective, noncompetitive inhibitor of the human (h) and rat (r) FSH receptors (FSHRs). Compound 1 selectively inhibited binding of [(125)I]hFSH with an IC(50) value of 5.4 +/- 2.3 micro M. Radioligand-binding assays were performed using the baculovirus expressed extracellular domain of hFSHR (BV-tFSHR) to demonstrate site-specific interaction. Compound 1 competed for [(125)I]hFSH binding to BV-tFSHR with an IC(50) value of 10 +/- 2.8 micro M. Functionally, compound 1 inhibited hFSH-induced cAMP accumulation and steroidogenesis in vitro with an IC(50) value of 3 +/- 0.6 micro M. Competition of compound 1 for binding to other glycoprotein hormone receptors and other G protein-coupled receptors demonstrated select activity for FHSRs. Compound 1 inhibited ovulation in immature and cycling adult rats. These data provide proof of concept that selective, small molecule antagonists can be designed for glycoprotein hormone receptors.