Development of Novel Male Contraceptives

Reversible Contraception in Males: An Obtainable Target?

The last few decades have brought contraception to the forefront of research, with great strides made in effectively targeting and optimizing the physiology, pharmacology, and delivery processes that prevent pregnancy. However, these advances still predominantly target female contraceptives for the prevention of contraception, whereas targeting the male sex has lagged far behind. This has led to a marked deficiency in safe and effective male contraceptive agents, resulting in a heavy dependence on female contraceptives to prevent unwanted and unplanned pregnancies. Current research in the veterinary field and in rodents highlights several promising avenues whereby novel, safe, and effective male contraceptive alternatives are being developed-with an emphasis on reduced side effects and reversibility potential. This review aims to discuss current and novel male contraceptives (both human and veterinary formulations) while highlighting their efficacy, advantages, and disadvantages.

Nanomaterials Solutions for Contraception: Concerns, Advances, and Prospects

Preventing unintentional pregnancy is one of the goals of a global public health policy to minimize effects on individuals, families, and society. Various contraceptive formulations with high effectiveness and acceptance, including intrauterine devices, hormonal patches for females, and condoms and vasectomy for males, have been developed and adopted over the last decades. However, distinct breakthroughs of contraceptive techniques have not yet been achieved, while the associated long-term adverse effects are insurmountable, such as endocrine system disorder along with hormone administration, invasive ligation, and slowly restored fertility after removal of intrauterine devices. Spurred by developments of nanomaterials and bionanotechnologies, advanced contraceptives could be fulfilled via nanomaterial solutions with much safer and more controllable and effective approaches to meet various and specific needs for women and men at different reproductive stages. Nanomedicine techniques have been extended to develop contraceptive methods, such as the targeted drug delivery and controlled release of hormone using nanocarriers for females and physical stimulation assisted vasectomy using functional nanomaterials via photothermal treatment or magnetic hyperthermia for males. Nanomaterial solutions for advanced contraceptives offer significantly improved biosafety, noninvasive administration, and controllable reversibility. This review summarizes the nanomaterial solutions to female and male contraceptives including the working mechanisms, clinical concerns, and their merits and demerits. This work also reviewed the nanomaterials that have been adopted in contraceptive applications. In addition, we further discuss safety considerations and future perspectives of nanomaterials in nanostrategy development for next-generation contraceptives. We expect that nanomaterials would potentially replace conventional materials for contraception in the near future.

Practice and development of male contraception: European Academy of Andrology and American Society of Andrology guidelines

BACKGROUNDS

Despite a wide spectrum of contraceptive methods for women, the unintended pregnancy rate remains high (45% in the US), with 50% resulting in abortion. Currently, 20% of global contraceptive use is male-directed, with a wide variation among countries due to limited availability and lack of efficacy. Worldwide studies indicate that >50% of men would opt to use a reversible method, and 90% of women would rely on their partner to use a contraceptive. Additional reasons for novel male contraceptive methods to be available include the increased life expectancy, sharing the reproductive risks among partners, social issues, the lack of pharma industry involvement and the lack of opinion makers advocating for male contraception.

AIM

The present guidelines aim to review the status regarding male contraception, the current state of the art to support the clinical practice, recommend minimal requirements for new male contraceptive development and provide and grade updated, evidence-based recommendations from the European Society of Andrology (EAA) and the American Society of Andrology (ASA).

METHODS

An expert panel of academicians appointed by the EAA and the ASA generated a consensus guideline according to the GRADE (Grading of Recommendations, Assessment, Development and Evaluation) system.

RESULTS

Sixty evidence-based and graded recommendations were produced on couple-centered communication, behaviors, barrier methods, semen analysis and contraceptive efficacy, physical agents, surgical methods, actions before initiating male contraception, hormonal methods, non-hormonal methods, vaccines, and social and ethical considerations.

CONCLUSION

As gender roles transform and gender equity is established in relationships, the male contribution to family planning must be facilitated. Efficient and safe male-directed methods must be evaluated and introduced into clinical practice, preferably reversible, either hormonal or non-hormonal. From a future perspective, identifying new hormonal combinations, suitable testicular targets, and emerging vas occlusion methods will produce novel molecules and products for male contraception.

Discovering a Reversible Male Contraceptive Agent Derived from Lonidamine

There is a huge demand for safe and effective non-hormonal male contraceptives to prevent unintended pregnancy, but research on male contraceptive drugs lacks far behind the pills for women. Lonidamine and its analog adjudin are two of the best studied potential male contraceptives. However, the acute toxicity of lonidamine and the subchronic toxicity of adjudin had impeded their development for male contraception. Here, we designed and synthesized a whole new series of molecules derived from lonidamine according to a structure ligand-based design strategy and obtained a new effective and reversible contraceptive agent (BHD), and their efficacy was demonstrated in male mice and rats. Results showed that BHD had a 100% contraceptive effect on male mice after 2 weeks following a single oral dose of BHD at 100 mg/kg body weight (b.w.) or 500 mg/kg b.w. treatments. The fertility of mice was reduced to 90 and 50% after 6 weeks with a single oral dose of BHD-100 and BHD-500 mg/kg b.w. treatments, respectively. We also revealed that BHD induced the apoptosis of spermatogenic cells rapidly and disrupted the blood-testis barrier effectively. It appears to be a new potential male contraceptive candidate for future development.

On-demand male contraception via acute inhibition of soluble adenylyl cyclase

Nearly half of all pregnancies are unintended; thus, existing family planning options are inadequate. For men, the only choices are condoms and vasectomy, and most current efforts to develop new contraceptives for men impact sperm development, meaning that contraception requires months of continuous pretreatment. Here, we provide proof-of-concept for an innovative strategy for on-demand contraception, where a man would take a birth control pill shortly before sex, only as needed. Soluble adenylyl cyclase (sAC) is essential for sperm motility and maturation. We show a single dose of a safe, acutely-acting sAC inhibitor with long residence time renders male mice temporarily infertile. Mice exhibit normal mating behavior, and full fertility returns the next day. These studies define sAC inhibitors as leads for on-demand contraceptives for men, and they provide in vivo proof-of-concept for previously untested paradigms in contraception; on-demand contraception after just a single dose and pharmacological contraception for men.

Why Is There Still No "Pill for Men"? Current Developments in Hormonal and Nonhormonal Medical Contraception for Men

Although hormonal contraception has been available to women for more than 60 yr, the only contraceptive options for men are still either a condom or vasectomy. This review presents current developments in hormonal and nonhormonal medical contraception for men, and perspectives for the future. Although a lot of scientific effort has been spent in identifying hormonal male contraception options in the past 40 yr, insufficient effectiveness and possible side effects mean that no official approvals have been obtained to date. Against this background, nonhormonal options for male contraception are the new field of interest. PATIENT SUMMARY: This review describes attempts to develop a reliable medical contraceptive for men, explains why there is still no "pill for men", and highlights how the future of medical contraception for men might look. For many reasons, there is an urgent need for male contraception in Europe and around the world.

Cellular and molecular basis for the action of retinoic acid in spermatogenesis

Spermatogenesis is a highly organized and regulated process that requires the constant production of millions of gametes over the reproductive lifetime of the mammalian male. This is possible because of an active stem cell pool and an ordered entry into the germ cell developmental sequence. The ordered entry is a result of the synthesis and action of retinoic acid allowing for the onset of spermatogonial differentiation and an irreversible commitment to spermatogenesis. The periodic appearance and actions of retinoic acid along the seminiferous tubules is a result of the interactions between germ cells and Sertoli cells that result in the generation and maintenance of the cycle of the seminiferous epithelium and is the subject of this review.

The testis-specific E3 ubiquitin ligase RNF133 is required for fecundity in mice

BACKGROUND

Ubiquitination is a post-translational modification required for a number of physiological functions regulating protein homeostasis, such as protein degradation. The endoplasmic reticulum (ER) quality control system recognizes and degrades proteins no longer needed in the ER through the ubiquitin-proteasome pathway. E2 and E3 enzymes containing a transmembrane domain have been shown to function in ER quality control. The ER transmembrane protein UBE2J1 is a E2 ubiquitin-conjugating enzyme reported to be essential for spermiogenesis at the elongating spermatid stage. Spermatids from Ube2j1 KO male mice are believed to have defects in the dislocation step of ER quality control. However, associated E3 ubiquitin-protein ligases that function during spermatogenesis remain unknown.

RESULTS

We identified four evolutionarily conserved testis-specific E3 ubiquitin-protein ligases [RING finger protein 133 (Rnf133); RING finger protein 148 (Rnf148); RING finger protein 151 (Rnf151); and Zinc finger SWIM-type containing 2 (Zswim2)]. Using the CRISPR/Cas9 system, we generated and analyzed the fertility of mutant mice with null alleles for each of these E3-encoding genes, as well as double and triple knockout (KO) mice. Male fertility, male reproductive organ, and sperm-associated parameters were analyzed in detail. Fecundity remained largely unaffected in Rnf148, Rnf151, and Zswim2 KO males; however, Rnf133 KO males displayed severe subfertility. Additionally, Rnf133 KO sperm exhibited abnormal morphology and reduced motility. Ultrastructural analysis demonstrated that cytoplasmic droplets were retained in Rnf133 KO spermatozoa. Although Rnf133 and Rnf148 encode paralogous genes that are chromosomally linked and encode putative ER transmembrane E3 ubiquitin-protein ligases based on their protein structures, there was limited functional redundancy of these proteins. In addition, we identified UBE2J1 as an E2 ubiquitin-conjugating protein that interacts with RNF133.

CONCLUSIONS

Our studies reveal that RNF133 is a testis-expressed E3 ubiquitin-protein ligase that plays a critical role for sperm function during spermiogenesis. Based on the presence of a transmembrane domain in RNF133 and its interaction with the ER containing E2 protein UBE2J1, we hypothesize that these ubiquitin-regulatory proteins function together in ER quality control during spermatogenesis.

Levonorgestrel Microneedle Array Patch for Sustained Release Contraception: Formulation, Optimization and In Vivo Characterization

Background: The goal of this work was to develop a levonorgestrel liposome-loaded microneedle array patch for contraception. Methods: Levonorgestrel-loaded liposome was formulated by a solvent injection technique, characterized, and studied. Results: The formulated liposomes were characterized for particle size (147 ± 8 nm), polydispersity index (0.207 ± 0.03), zeta potential (−23 ± 4.25 mV), drug loading (18 ± 3.22%) and entrapment efficiency (85 ± 4.34%). A cryo high-resolution transmission electron microscopy and cryo field emission gun scanning electron microscopy study showed spherical shaped particles with a smooth surface. The in vitro drug release and in vivo pharmacokinetic study showed sustained behaviour of Levonorgestrel for 28 days. Conclusion: The levonorgestrel liposome-loaded microneedle array patch showed better contraception than the drug-loaded microneedle array patch.

Immediate detachment of microneedles by interfacial fracture for sustained delivery of a contraceptive hormone in the skin

Despite their high efficacy and safety, long-acting contraceptive methods are underutilized among women in some settings because they usually require injection or implantation by healthcare personnel. Here, we report a self-administrable microneedle (MN) patch for the rapid administration of a sustained-release contraceptive hormone delivery system into the skin that increases the simplicity and reliability of the MN delivery. We developed an immediate microneedle detachment system using a porous patch backing that has sufficient strength during MN insertion into skin under compression, but enables immediate detachment (< 1 s) of the MNs due to fracture at the MN - backing interface upon patch removal under tension from the skin surface. After patch application, the removed patch produced no biohazardous sharps waste, and was designed to achieve long-acting contraception by formulating poly(lactic-co-glycolic acid) MNs to slowly release the contraceptive hormone levonorgestrel for up to 1 month. Our combined strategy using immediate MN detachment in the skin and sustained drug delivery from the MNs could facilitate greater access to long-acting contraception by providing a simple and convenient option for self-administered, long-acting contraception.

Pharmacological Inactivation of CatSper Blocks Sperm Fertilizing Ability Independently of the Capacitation Status of the Cells: Implications for Non-hormonal Contraception

Cation channel of sperm (CatSper), the main sperm-specific Ca2+ channel, plays a key role in mammalian fertilization, and it is essential for male fertility, becoming an attractive target for contraception. Based on this, in the present work, we investigated the effects of CatSper inactivation on in vitro and in vivo sperm fertilizing ability and the mechanisms underlying such effects. Exposure of cauda epididymal mouse sperm to different concentrations (1-20 μM) of the potent CatSper inhibitor HC-056456 (HC) during in vitro capacitation showed no effects on sperm viability but significantly affected Ca2+ entry into the cells, progressive motility, protein tyrosine phosphorylation, induced acrosome reaction, and hyperactivation, as well as the sperm's ability to in vitro fertilize cumulus oocyte complexes and zona-free eggs. Whereas the presence of HC during gamete coincubation did not affect in vitro fertilization, exposure of either non-capacitating or already capacitated sperm to HC prior to gamete coincubation severely reduced fertilization, indicating that sperm function is affected by HC when the cells are incubated with the drug before sperm-egg interaction. Of note, insemination of HC-treated sperm into the uterus significantly or completely reduced the percentage of oviductal fertilized eggs showing, for the first time, the effects of a CatSper inhibitor on in vivo fertilization. These observations, together with the finding that HC affects sperm fertilizing ability independently of the sperm capacitation status, provide further insights on how CatSper regulates sperm function and represent a solid proof of concept for developing a male/female non-hormonal contraceptive based on the pharmacological blockage of CatSper activity.

SLC22A14 is a mitochondrial riboflavin transporter required for sperm oxidative phosphorylation and male fertility

Ablation of Slc22a14 causes male infertility in mice, but the underlying mechanisms remain unknown. Here, we show that SLC22A14 is a riboflavin transporter localized at the inner mitochondrial membrane of the spermatozoa mid-piece and show by genetic, biochemical, multi-omic, and nutritional evidence that riboflavin transport deficiency suppresses the oxidative phosphorylation and reprograms spermatozoa energy metabolism by disrupting flavoenzyme functions. Specifically, we find that fatty acid β-oxidation (FAO) is defective with significantly reduced levels of acyl-carnitines and metabolites from the TCA cycle (the citric acid cycle) but accumulated triglycerides and free fatty acids in Slc22a14 knockout spermatozoa. We demonstrate that Slc22a14-mediated FAO is essential for spermatozoa energy generation and motility. Furthermore, sperm from wild-type mice treated with a riboflavin-deficient diet mimics those in Slc22a14 knockout mice, confirming that an altered riboflavin level causes spermatozoa morphological and bioenergetic defects. Beyond substantially advancing our understanding of spermatozoa energy metabolism, our study provides an attractive target for the development of male contraceptives.

Vasectomy and male sexual dysfunction risk: A systematic review and meta-analysis

BACKGROUND

Unintended pregnancy is popular all over the world, accounting for 40% to 50% of all pregnancies. The condition not only exerts pressure on the relationship of couples and severely impacts the quality of life, but also imposes a heavy burden on the health of women and child. Recently, more than 220 million couples have chosen to be sterilized to obtain contraception, 47.3% of married couples select sterilization, of which vasectomy accounts for 17.1%. Vasectomy is currently the most convenient and effective method of male contraception. We will perform the systematic review and meta-analysis to assess the correlation between vasectomy and male sex dysfunction and provide evidence-based evidence for the couple METHODS:: The electronic databases of MEDLINE, PubMed, Web of Science, EMBASE, Clinicaltrials.org., China National Knowledge Infrastructure Database (CNKI), Wan fang Database, China Biology Medicine Database (CBM), VIP Science Technology Periodical Database, Chinese Clinical Trial Registry, and Cochrane Library will be retrieved before November 20, 2021. We will search English literature and Chinese literature with proper Medical Subject Heading or text key words. RevMan 5.3 and Stata 14.0 will be used for Systematic review and Meta-analysis. This protocol reported in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses Protocols (PRISMA-P) statement, and we will report the systematic review by following the PRISMA statement.

CONCLUSION AND DISSEMINATION

The aim of this study was to evaluate the effect of vasectomy on the sexual function of patients after operation. The results will be published in a public issue journal to provide evidence-based medical evidence for urologists and andrologists to make clinical decisions.

REGISTRATION INFORMATION

INPLASY202080014.

Retinoic acid receptor antagonists for male contraception: current status†

Retinoic acid receptor alpha (RARA), a nuclear receptor protein, has been validated as a target for male contraception by gene knockout studies and also pharmacologically using a pan-retinoic acid receptor antagonist. Retinoic acid receptor alpha activity is indispensable for the spermatogenic process, and therefore its antagonists have potential as male contraceptive agents. This review discusses the effects of systematic dosing regimen modifications of the orally bioavailable and reversible pan-antagonist BMS-189453 as well as studies with the alpha-selective antagonists BMS-189532 and BMS-189614 in a murine model. We also provide an overview of structure-activity studies of retinoic acid receptor alpha antagonists that provide insight for the design of novel alpha-selective ligands.

BET proteins: Investigating BRDT as a potential target for male contraception

While many contraception options are available for women, birth control methods for men are limited to condoms and vasectomy. Past research into male contraceptives has focused on hormonal options but the associated side effects have thus far precluded this method from reaching the market. Non-hormonal male contraceptives and vas occlusion have also been explored, but to date no method has progressed past clinical testing. Recent interest in epigenetic research has unveiled a new potential non-hormonal male contraceptive target: the testis-specific bromodomain BRDT. Potent inhibitors for bromodomain-containing proteins are described in the literature, but a BRDT-specific compound has yet to be designed, prepared and tested. The high similarity between bromodomain proteins of the BET family makes development of selective and specific inhibitors both difficult and necessary. Selective inhibition of BRDT by a small molecule is an exciting new target in the search for a new non-hormonal male contraceptive.