The urgent need for innovation in contraception.

Despite advancements in medicine over the past decades, there exists a significant unmet global need for new and improved contraceptive methods for men and women. The development of innovative contraceptives will be facilitated via advancements in biomedical science, biomedical engineering, and drug development technologies. This article describes the need for new methods, opportunities afforded by advancements in biomedical science, strategies being employed to advance innovative novel methods, value of drug development accelerators and the need for industry involvement to provide men and women worldwide greater reproductive autonomy.

The new contraceptive revolution: developing innovative products outside of industry†,‡.

A significant global unmet need for new contraceptive options for both women and men remains due to side effect profiles, medical concerns, and inconvenience of many currently available products. The pharmaceutical industry has largely abandoned early research and development for contraception and will not likely engage to bring new products to the market unless they have been significantly de-risked by showing promise in early phase clinical trials. This lack of interest by big pharma comes at a time when scientific and technological advances in biology and medicine are creating more opportunities than ever for the development of new and innovative drug products. Novel partnerships between the academic sector, small biotechnology companies, foundations, non-government organizations (NGOs), and the federal government could accelerate the development of new contraceptive products. We discuss the challenges and opportunities that we have encountered as an NGO with a mission to develop novel contraceptive products for low- and middle-income countries and how it differs from developing products for higher-income markets. We hope that our experiences and "lessons learned" will be of value to others as they proceed down the product development path, be it for female or male or for hormonal or nonhormonal contraceptives.

The uniqueness of on-demand male contraception.

Because nearly half of pregnancies worldwide are unintended, available contraceptive methods are inadequate. Moreover, due to the striking imbalance between contraceptive options available for men compared to the myriad of options available to women, there is an urgent need for new methods of contraception for men. This review summarizes ongoing efforts to develop male contraceptives highlighting the unique aspects particular to on-demand male contraception, where a man takes a contraceptive only when and as often as needed.

Stage-specific gene expression is a fundamental characteristic of rat spermatogenic cells and Sertoli cells.

Mammalian spermatogenesis is a complex biological process that occurs within a highly organized tissue, the seminiferous epithelium. The coordinated maturation of spermatogonia, spermatocytes, and spermatids suggests the existence of precise programs of gene expression in these cells and in their neighboring somatic Sertoli cells. The objective of this study was to identify the genes that execute these programs. Rat seminiferous tubules at stages I, II-III, IV-V, VI, VIIa,b, VIIc,d, VIII, IX-XI, XII, and XIII-XIV of the cycle were isolated by microdissection, whereas Sertoli cells, spermatogonia plus early spermatocytes, pachytene spermatocytes, and round spermatids were purified from enzymatically dispersed testes. Microarray analysis by using Rat Genome 230 2.0 arrays identified 16,971 probe sets that recognized testicular transcripts, and 398 of these were identified as testis-specific. Expression of 1,286 probe sets were found to differ at least 4-fold between two cell types and also across the stages of the cycle. Pathway and annotated cluster analyses of those probe sets predicted that entire biological pathways and processes are regulated cyclically in specific cells. Important among these are the cell cycle, DNA repair, and embryonic neuron development. Taken together, these data indicate that stage-regulated gene expression is a widespread and fundamental characteristic of spermatogenic cells and Sertoli cells.

The "soluble" adenylyl cyclase in sperm mediates multiple signaling events required for fertilization.

Mammalian fertilization is dependent upon a series of bicarbonate-induced, cAMP-dependent processes sperm undergo as they "capacitate," i.e., acquire the ability to fertilize eggs. Male mice lacking the bicarbonate- and calcium-responsive soluble adenylyl cyclase (sAC), the predominant source of cAMP in male germ cells, are infertile, as the sperm are immotile. Membrane-permeable cAMP analogs are reported to rescue the motility defect, but we now show that these "rescued" null sperm were not hyperactive, displayed flagellar angulation, and remained unable to fertilize eggs in vitro. These deficits uncover a requirement for sAC during spermatogenesis and/or epididymal maturation and reveal limitations inherent in studying sAC function using knockout mice. To circumvent this restriction, we identified a specific sAC inhibitor that allowed temporal control over sAC activity. This inhibitor revealed that capacitation is defined by separable events: induction of protein tyrosine phosphorylation and motility are sAC dependent while acrosomal exocytosis is not dependent on sAC.

2-phenyl-4-piperazinylbenzimidazoles: orally active inhibitors of the gonadotropin releasing hormone (GnRH) receptor.

Antagonism of the gonadotropin releasing hormone (GnRH) receptor has shown positive clinical results in numerous reproductive tissue disorders such as endometriosis, prostate cancer and others. Traditional therapy has been limited to peptide agonists and antagonists. Recently, small molecule GnRH antagonists have emerged as potentially new treatments. This article describes the discovery of 2-phenyl-4-piperazinylbenzimidazoles as small molecule GnRH antagonists with nanomolar potency in in vitro binding and functional assays, excellent bioavailability (rat %F>70) and demonstrated oral activity in a rat model having shown significant serum leuteinizing hormone (LH) suppression.

Approaches to the identification of new nonhormonal targets for male contraception.

Fertility control is a global health issue with major personal and societal impact. Although, currently, there are several different options for contraception, the technologies behind these are antiquated, and the options for male-based contraception (i.e., withdrawal, condom and vasectomy) are inadequate. The genomic, proteomic and bioinformatic revolutions have provided new tools and new targets for contraceptive development, and the results of such approaches have identified gene products that play critical roles in male reproduction, thus expanding the array of potential targets for novel and innovative male-based contraceptives. This article will review the types of targets being considered in the development of nonhormonal male contraceptives and the technologies used to identify and validate these targets.

Identification of testis-specific male contraceptive targets: insights from transcriptional profiling of the cycle of the rat seminiferous epithelium and purified testicular cells.

In an effort to identify novel targets for the development of nonhormonal male contraceptives, genome-wide transcriptional profiling of the rat testis was performed. Specifically, enzymatically purified spermatogonia plus early spermatocyctes, pachytene spermatocytes, round spermatids, and Sertoli cells was analyzed along with microdissected rat seminiferous tubules at stages I, II-III, IV-V, VI, VIIa,b, VIIc,d, VIII, IX- XI, XII, XIII-XIV of the cycle of the seminiferous epithelium using RAE 230_2.0 microarrays. The combined analysis of these studies identified 16,971 expressed probe sets on the array. How these expression data, combined with additional bioinformatic data analysis and quantitative reverse transcriptase polymerase chain reaction (qRT-PCR) analysis, led to the identification of 58 genes that have 1000-fold higher expression transcriptionally in the testis when compared to over 20 other nonreproductive tissues is described. The products of these genes may play important roles in testicular and/or sperm function, and further investigation on their utility as nonhormonal contraceptive targets is warranted. Moreover, these microarray data have been used to expedite the identification of a mutation in RIKEN cDNA 2410004F06 gene as likely being responsible for spermatogenic failure in a line of infertile mice generated by N-ethyl-N-nitrosourea (ENU) mutagenesis. The microarray data and the qRT-PCR data described are available in the Mammalian Reproductive Genetics database (http://mrg.genetics.washington.edu/).

Gene expression during development of fetal and adult Leydig cells.

In rats and mice, Leydig cells are formed as two morphologically and functionally different generations. The first generation develops in utero, from undifferentiated stem Leydig cells (SLCs) that differentiate into fetal Leydig cells (FLCs). After birth, SLCs that may differ from the fetal SLCs undergo lineage-specific commitment and give rise to adult Leydig cells (ALCs). The intermediates of ALCs first become apparent by day 11 postpartum. These first-appearing intermediates, progenitor Leydig cells (PLCs), are spindle shaped and identifiable as steroidogenic because they express luteinizing hormone receptor (LHR) and 3beta-hydroxysteroid dehydrogenase (3betaHSD). The next step in the transition of PLCs to ALCs is the appearance of the immature Leydig cells (ILCs), most commonly seen in the testis during days 28 to 56 postpartum. ILCs have a more abundant smooth endoplasm reticulum (SER), the network of membranes providing a scaffold for steroidogenic enzyme localization, compared to PLCs, but are considered immature because they secrete higher levels of 5alpha-reduced androgen than testosterone. ILCs undergo a final division before ALC steroidogenic function matures by postnatal day 56. ALCs mark the point of maximum differentiation, and at this stage, the Leydig cell secretes testosterone at the highest rate. In this review, trends of gene expression during development of the two Leydig-cell generations, and recent information from gene profiling by microarray, are evaluated. The expression profiles are distinct, indicating that FLCs and ALCs may originate from separate pools of stem cells.

Gene expression profiling and its practice in drug development.

The availability of sequenced genomes of human and many experimental animals necessitated the development of new technologies and powerful computational tools that are capable of exploiting these genomic data and ask intriguing questions about complex nature of biological processes. This gave impetus for developing whole genome approaches that can produce functional information of genes in the form of expression profiles and unscramble the relationships between variation in gene expression and the resulting physiological outcome. These profiles represent genetic fingerprints or catalogue of genes that characterize the cell or tissue being studied and provide a basis from which to begin an investigation of the underlying biology. Among the most powerful and versatile tools are high-density DNA microarrays to analyze the expression patterns of large numbers of genes across different tissues or within the same tissue under a variety of experimental conditions or even between species. The wide spread use of microarray technologies is generating large sets of data that is stimulating the development of better analytical tools so that functions can be predicted for novel genes. In this review, the authors discuss how these profiles are being used at various stages of the drug discovery process and help in the identification of new drug targets, predict the function of novel genes, and understand individual variability in response to drugs.

Identification of epididymis-specific transcripts in the mouse and rat by transcriptional profiling.

As part of our efforts to identify novel contraceptive targets in the epididymis we performed transcriptional profiling on each of the 10 and 19 segments of the mouse and rat epididymidis, respectively, using Affymetrix whole genome microarrays. A total of 17 096 and 16 360 probe sets representing transcripts were identified as being expressed in the segmented mouse and rat epididymal transcriptomes, respectively. Comparison of the expressed murine transcripts against a mouse transcriptional profiling database derived from 22 other mouse tissues identified 77 transcripts that were expressed uniquely in the epididymis. The expression of these genes was further evaluated by reverse transcription polymerase chain reaction (RT-PCR) analysis of RNA from 21 mouse tissues. RT-PCR analysis confirmed epididymis-specific expression of Defensin Beta 13 and identified two additional genes with expression restricted only to the epididymis and testis. Comparison of the 16 360 expressed transcripts in the rat epididymis with data of 21 other tissues from a rat transcriptional profiling database identified 110 transcripts specific for the epididymis. Sixty-two of these transcripts were further investigated by qPCR analysis. Only Defensin 22 (E3 epididymal protein) was shown to be completely specific for the epididymis. In addition, 14 transcripts showed more than 100-fold selective expression in the epididymis. The products of these genes might play important roles in epididymal and/or sperm function and further investigation and validation as contraceptive targets are warranted. The results of the studies described in this report are available at the Mammalian Reproductive Genetics (MRG) Database (http://mrg.genetics.washington.edu/).

Analysis of the human sperm proteome.

As part of our effort to identify putative protein targets for the development of male contraceptives, we performed an in-depth proteomic analysis of human sperm by liquid chromatography and tandem mass spectrometry. Motile sperm were collected from a single fertile individual and fractionated into detergent-soluble and detergent-insoluble fractions. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis separation of these fractions, followed by manual cutting of the gel, yielded 35 gel sections for each fraction to include proteins across the full range of electrophoretic mobility. Proteomic analysis of these gel sections identified more than 1,760 proteins with high confidence, with 1,350 proteins identified in the soluble fraction, 719 identified in the insoluble fraction, and 309 identified in both fractions. This characterization of the human sperm proteome provides a high-resolution, physiologically relevant index of the proteins that comprise human sperm.

Status and future direction of male contraceptive development.

Control of fertility constitutes a global health issue, as overpopulation and unintended pregnancy have both major personal and societal impact. Although the contraceptive revolution in the 1960s following the development of hormonal-based oral contraceptives for women has had a major impact on societal dynamics in several cultures, little product innovation has occurred since then. One solution to this global health issue lies in the development of new and innovative contraceptives for both women and men, the goal of which is to provide a range of options for people at all stages and walks of life. Currently, three options for male-based contraception exist (i.e. withdrawal, condoms and vasectomy), and these are acknowledged as woefully inadequate. Introduction of new forms of male contraception based on both hormonal and non-hormonal paradigms are wanted and needed; this need is now becoming recognized by both the public and private sectors. New and innovative products will come from our knowledge of the unique physiology and genetics of reproduction, as well as by exploiting existing and future genomics, proteomics and protein network platforms.

GnRH agonists and antagonists in cancer therapy.

Gonadotropin releasing hormone (GnRH) is a hypothalamic decapeptide that binds to GnRH receptors on pituitary gonadotrope cells to modulate the synthesis and secretion of the gonadotropins, luteinizing hormone (LH) and follicle-stimulating hormone (FSH). These gonadotropins in turn regulate gonadal steroidogenesis and gametogenesis. Chemical characterization and structure-activity analysis of GnRH variants containing systematic amino acid substitutions led to the discovery of GnRH superagonists and antagonists. These peptides are widely used for the treatment of clinical conditions in which modulation of or interference with sex hormone production is beneficial to prevent development or progression of benign conditions (e.g. endometriosis, uterine fibroids) or malignant tumors (e.g. breast, ovarian, endometrial and prostate carcinoma). When compared to native GnRH, GnRH superagonists have increased potency for the short-term release of gonadotropins. However, they show paradoxical action in that chronic treatment with superagonists results in inhibition of gonadotropin production as a result of desensitization of the gonadotropes and down regulation of its receptor. In contrast, GnRH antagonists produce a rapid and dose-dependent suppression of gonadotropin release by competitive blockade of the GnRH receptors without any initial stimulatory effect as seen with superagonists. In recent years, a search for peptidomimetic compounds to replace peptides as therapeutic agents has been undertaken to find compounds with higher affinity for the GnRH receptor but do not have the disadvantages of peptides. Such efforts have resulted in the identification and development of small-molecule non-peptide compounds that are sufficiently stable in vivo and possess favorable pharmacological parameters comparable to peptide antagonists. Some of these compounds are being tested in human volunteers and the preliminary results are very encouraging.