Male contraception: what is on the horizon?

Male contraception remains an important area of research. Methods can inhibit sperm production or can be targeted to inhibit sperm functions such as motility, orientation or interaction with the egg. Hormonal methods appear to be safe and effective in proof of concept studies but efforts are underway to improve delivery options or lead time until full efficacy is achieved. Nonhormonal methods are based on numerous targets that impact sperm production or function. Several agents that inhibit the sperm-specific or testis-specific targets have been identified and studies in animals have shown promising results.

Brdt Bromodomains Inhibitors and Other Modern Means of Male Contraception.

Compared to efficient and secure female contraception, a vasectomy and condoms are the only options for men. The choice of male contraceptive methods is limited, so contraception mainly rests on the shoulders of women. Several concepts are considered: testosterone administration--inhibiting pituitary secretion of lutropin (LH) and follicle stimulating hormone (FSH), progestogen--affecting the secretion of gonadotropin and gonadoliberin (GnRH) antagonists. New potential targets for non-hormonal male contraception were discovered: glyceraldehyde-3-phosphate-dehydrogenase (GAPDHS)--specific to male germ cells and voltage-gated cation channel (CatSper). Both are responsible for sperm motility. Drugs such as thioridazine used in schizophrenia treatment and phenoxybenzamine (antihypertensive activity) exhibit a contraceptive effect. Similar action exhibits an analogue of lonidamine--adjudin and an antagonist of retinoic acid receptors (BMS-189453). Researchers are working on a contraceptive vaccine, whose active ingredient is epididymal protease inhibitor (Eppin). Another promising method acts by blocking Bromodomain testis-specific proteins (Brdt) involved in the process of spermatogenesis. JQ1-the Brdt inhibitor causes reversible infertility without affecting the endocrine signaling pathways. A recent discovery of Juno as the binding partner for Izumo1 identifies these proteins as the cell-surface receptor pair, essential for gamete recognition and this interaction can be inhibited by an anti-Juno monoclonal antibody. Our review shows that the situation of men can change and investigators are close to the optimal solution. In the near future men will be able to choose the best contraceptive suited to their needs.

Pharmacologic development of male hormonal contraceptive agents.

The world population continues to increase dramatically despite the existence of contraceptive technology. The use of male hormonal contraception may help in preventing un intended pregnancies and managing future population growth. Male hormonal contraception relies on the administration of exogenous hormones to suppress spermatogenesis. Clinical trials have tested several regimens using testosterone, alone or in combination with a progestin. These regimens were shown to be >90% effective in preventing conception and were not associated with serious adverse events.

Recent methodological advances in male hormonal contraception.

Landmark WHO-sponsored trials showed decades ago that male hormonal contraception (MHC) is an effective male-directed contraceptive approach. Considerable progress has been made particularly in the last 5 years, establishing for the first time the reversibility of MHC and its short-term safety. Methodological advances in recent years include the pooling of information and individual-level integrated analysis; the first-time use of centralized semen analysis and fluorescence to detect low sperm concentrations; the establishment of sperm quality reference ranges in fertile men; the measurement of blood steroid concentrations by gas chromatography/mass spectrometry; and the inclusion of placebo groups to delineate clearly possible adverse effects of androgens and progestins in men. We report integrated analyses of factors that are important in predicting suppression and recovery of spermatogenesis after MHC clinical trials for the past 15 years. These are the best data available and will provide guidance and reassurance for the larger-scale Phase III specific regimen efficacy studies that will be required to bring MHC to the population (market).

Lack of gonadal protection by medroxyprogesterone acetate-induced transient medical castration during chemotherapy for testicular cancer.

The serum FSH levels were analysed in 24 testicular cancer patients 3 to 9 years after intensive chemotherapy. Sperm cell counts were performed in 12 patients. In all cases a temporary medical castration had been achieved during intensive chemotherapy by the use of medroxyprogesterone acetate (MPA) (500 mg daily per os). The hormone treatment was initiated on day 1 of the first chemotherapy cycle. Thirteen additional patients did not receive this hormone treatment but were treated by similar chemotherapy. The latter patients served as a control group. There was a tendency towards higher FSH levels in the MPA-treated patients than in the controls. Following treatment, serum testosterone was significantly lower in patients who had received MPA during their intensive chemotherapy than in the controls. There was no difference between the groups with regard to recovery of sperm cell production after chemotherapy. An MPA-induced medical castration during intensive chemotherapy in testicular cancer patients is ineffective in protecting the remaining testis against treatment-induced damage to spermatogenesis, at least if hormone treatment is started simultaneously with chemotherapy.