Reversibility of Vasalgel™ male contraceptive in a rabbit model

Male animal sterilization: history, current practices, and potential methods for replacing castration

Sterilization and castration have been synonyms for thousands of years. Making an animal sterile meant to render them incapable of producing offspring. Castration or the physical removal of the testes was discovered to be the most simple but reliable method for managing reproduction and sexual behavior in the male. Today, there continues to be global utilization of castration in domestic animals. More than six hundred million pigs are castrated every year, and surgical removal of testes in dogs and cats is a routine practice in veterinary medicine. However, modern biological research has extended the meaning of sterilization to include methods that spare testis removal and involve a variety of options, from chemical castration and immunocastration to various methods of vasectomy. This review begins with the history of sterilization, showing a direct link between its practice in man and animals. Then, it traces the evolution of concepts for inducing sterility, where research has overlapped with basic studies of reproductive hormones and the discovery of testicular toxicants, some of which serve as sterilizing agents in rodent pests. Finally, the most recent efforts to use the immune system and gene editing to block hormonal stimulation of testis function are discussed. As we respond to the crisis of animal overpopulation and strive for better animal welfare, these novel methods provide optimism for replacing surgical castration in some species.

[Acceptability of innovative male contraceptive methods among major of age heterosexual adult men in France in 2021]

INTRODUCTION

New methods of male contraception are being studied: male hormonal contraception, reversible occlusion of the vas deferens and thermal contraception. This study aimed to evaluate the acceptability of these methods among men.

MATERIAL AND METHODS

We carried out an opinion survey from July to November 2021, through an anonymous questionnaire distributed in France on the internet. The subjects were adult, heterosexual men.

RESULTS

Of the 1545 connections to the questionnaire, we analyzed the 905 complete questionnaires. Seventy three percent of men say they are in favor of adopting an innovative male contraceptive method as their primary contraception: 64% in favor of reversible occlusion of the vas deferens, 22% in favor of male hormonal contraception and 13% in favor of thermal contraception.

CONCLUSION

Despite its limitations, this study shows that a significant part of the male population is interested in innovative methods of contraception that concern them. This should encourage continued research in this area.

LEVEL OF EVIDENCE: 4

Male contraception: narrative review of ongoing research

BACKGROUND

Since the release of the combined oral contraceptive pill in 1960, women have shouldered the burden of contraception and family planning. Over 60 years later, this is still the case as the only practical, effective contraceptive options available to men are condoms and vasectomy. However, there are now a variety of promising hormonal and non-hormonal male contraceptive options being studied. The purpose of this narrative review is to provide clinicians and laypeople with focused, up-to-date descriptions of novel strategies and targets for male contraception. We include a cautiously optimistic discussion of benefits and potential drawbacks, highlighting several methods in preclinical and clinical stages of development.

RESULTS

As of June 2023, two hormonal male contraceptive methods are undergoing phase II clinical trials for safety and efficacy. A large-scale, international phase IIb trial investigating efficacy of transdermal segesterone acetate (Nestorone) plus testosterone gel has enrolled over 460 couples with completion estimated for late 2024. A second hormonal method, dimethandrolone undecanoate, is in two clinical trials focusing on safety, pharmacodynamics, suppression of spermatogenesis and hormones; the first of these two is estimated for completion in December 2024. There are also several non-hormonal methods with strong potential in preclinical stages of development.

CONCLUSIONS

There exist several hurdles to novel male contraception. Therapeutic development takes decades of time, meticulous work, and financial investment, but with so many strong candidates it is our hope that there will soon be several safe, effective, and reversible contraceptive options available to male patients.

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.

Recent progress in advanced biomaterials for long-acting reversible contraception

Unintended pregnancy is a global issue with serious ramifications for women, their families, and society, including abortion, infertility, and maternal death. Although existing contraceptive strategies have been widely used in people's lives, there have not been satisfactory feedbacks due to low contraceptive efficacy and related side effects (e.g., decreased sexuality, menstrual cycle disorder, and even lifelong infertility). In recent years, biomaterials-based long-acting reversible contraception has received increasing attention from the viewpoint of fundamental research and practical applications mainly owing to improved delivery routes and controlled drug delivery. This review summarizes recent progress in advanced biomaterials for long-acting reversible contraception via various delivery routes, including subcutaneous implant, transdermal patch, oral administration, vaginal ring, intrauterine device, fallopian tube occlusion, vas deferens contraception, and Intravenous administration. In addition, biomaterials, especially nanomaterials, still need to be improved and prospects for the future in contraception are mentioned.

Male contraception: What do women think?

INTRODUCTION

Women currently bear the most responsibility in contraception, with a wide choice of methods, while only a few existing male contraceptives are available. However, it has been shown that men are willing to get involved in birth control and to control their own fertility. Our research was focused on female population and a survey was carried out to explore women's perceptions of male contraception.

METHODS

An observational quantitative cross-sectional study using a self-administered-questionnaire was carried out between November 2019 and February 2020. All women aged from 16-years-old to menopause completing the questionnaire were included. Descriptive statistical analyses were conducted, qualitative variables were expressed as counts and frequency.

RESULTS

In total, 379 interpretable completed questionnaires were included. Among the women, 69.7% were in favour of letting men deal with contraception, without referring to a specific method. After having been made aware of the medical information concerning existing male contraceptives and those in development, the proportion of women in favour dropped to 46.7%. The most acceptable method for a majority of women was the male pill, which is still being developed. The majority (78.4%) of the women in our survey felt insufficiently informed about male contraception.

DISCUSSION

In our study, women seemed to want to share contraceptive responsibility with men, but the lack of information and of acceptable contraception methods available remained an obstacle. Although larger-scale studies are needed to confirm these results, the development of a wider range of male contraception methods seems to be what both men and women have long been expecting.

Polymeric-based drug delivery systems for veterinary use: State of the art

One of the challenges to the success of veterinary pharmacotherapy is the limited number of drugs and dosage forms available exclusively to this market, due to the interspecies variability of animals, such as anatomy, physiology, pharmacokinetics, and pharmacodynamics. For this reason, studies in this area have become a highlight, since they are still scarce in comparison with those on human drug use. To overcome many limitations related to the bioavailability, efficacy, and safety of pharmacotherapy in animals, especially livestock and domestic animals, polymers-based drug delivery systems are promising tools if they guarantee greater selectivity and less toxicity in dosage forms. In addition, these tools may be developed according to the great interspecies variability. To contribute to these discussions, this paper provides an updated review of the major polymer-based drug delivery systems projected for veterinary use. Traditional and innovative drug delivery systems based on polymers are presented, with an emphasis on films, microparticles, micelles, nanogels, nanoparticles, tablets, implants and hydrogel-based drug delivery systems. We discuss important concepts for the veterinarian about the mechanisms of drug release and, for the pharmacist, the advantages in the development of pharmaceutical forms for the animal population. Finally, challenges and opportunities are presented in the field of pharmaceutical dosage forms for veterinary use in response to the interests of the pharmaceutical industry.

Emerging approaches to male contraception

Despite significant interests in contraception by men, effective methods of male contraception are limited to vasectomy and condoms. Recently, there have been several promising advances in male contraceptive research. This review will update readers on recent research in both hormonal and nonhormonal approaches to male contraception. Hormonal approaches to male contraception have been stymied by adverse effects, formulations requiring injections or implants, a 5% to10% nonresponse rate, as well as poor understanding of user acceptability. In the last several years, research has focused on novel, orally bioavailable androgens such as dimethandrolone undecanoate and 11β-methyl-19-nor-testosterone. Additionally, combinations of a topical testosterone gel combined with a gel containing segesterone acetate, a potent progestin, have shown promise in clinical trials recently. Simultaneously, significant preclinical progress has been made in several approaches to nonhormonal male contraceptives, including compounds that inhibit sperm motility such as eppin, compounds that inhibit retinoic acid binding or biosynthesis, and reversible approaches to obstruction of the vas deferens. It is imperative for these areas of research to continue making strides so that there is a gamut of contraceptive options for couples to choose from. Some of these approaches will hopefully reach clinical utility soon, greatly improving contraceptive choice for couples.

Male Contraception

Unintended pregnancy is a global public health problem. Despite a variety of female contraceptive options, male contraceptive options are limited to the condom and vasectomy. Condoms have high failure rates and surgical vasectomy is not reliably reversible. There is a global need and desire for novel male contraceptive methods. Hormonal methods have progressed the furthest in clinical development and androgen plus progestin formulations hold promise as a marketable, reversible male contraceptive over the next decade. Investigators have tested androgen plus progestin approaches using oral, transdermal, subdermal, and injectable drug formulations and demonstrated the short-term safety and reversibility of hormonal male contraception. The most commonly reported side effects associated with hormonal male contraception include weight gain, acne, slight suppression of serum high-density cholesterol, mood changes, and changes in libido. Efficacy trials of hormonal male contraceptives have demonstrated contraceptive efficacy rates greater than that of condoms. Although there has been less progression in the development of nonhormonal male contraceptives, potentially reversible vaso-occlusive methods are currently in clinical trials in some countries. Various studies have confirmed both men and women's desire for novel male contraceptives. Barriers to development include an absence of investment from pharmaceutical companies, concerns regarding side effects and spermatogenic rebound with hormonal methods, and lack of clear reversibility and proven effectiveness of nonhormonal methods. The ultimate availability of male contraceptives could have an important impact on decreasing global unintended pregnancy rates (currently 40% of all pregnancies) and will be a step towards reproductive justice and greater equity in family planning.

Biomaterials and Contraception: Promises and Pitfalls

The present state of reproductive and sexual health around the world reveals disparities in contraceptive use and effectiveness. Unintended pregnancy and sexually transmitted infection transmission rates remain high even with current prevention methods. The 20th century saw a contraceptive revolution with biomedical innovation driving the success of new contraceptive technologies with central design concepts and materials. Current modalities can be broadly categorized according to their mode of function: reversible methods such as physical/chemical barriers or hormonal delivery devices via systemic (transdermal and subcutaneous) or localized (intrauterine and intravaginal) administration, and nonreversible sterilization procedures such as tubal ligation and vasectomy. Contraceptive biomaterials are at present dominated by well-characterized elastomers such as polydimethylsiloxane and ethylene vinyl acetate due to their favorable material properties and versatility. Contraceptives alter the normal function of cellular components in the reproductive systems to impair fertility. The purpose of this review is to highlight the bioengineering design of existing methods, explore novel adaptations, and address notable shortcomings in current contraceptive technologies.

Recent Developments in Male Contraception

Unplanned pregnancies are an ongoing global burden, posing health and economic risks for women, children, and families. Advances in male contraception have been historically stymied by concerning failure rates, problematic side effects, and perceived market limitations. However, increased interest in reliable and reversible options for male contraception have resulted in resurgent efforts to introduce novel contraceptives for men. Hormonal male contraception relies on exogenous androgens and progestogens that suppress gonadotropin production, thereby suppressing testicular testosterone and sperm production. In many men, effective suppression of spermatogenesis can be achieved by androgen-progestin combination therapy. Small-scale contraceptive efficacy studies in couples have demonstrated effectiveness and reversibility with male hormonal methods, but side effects related to mood, sexual desire and cholesterol remain concerning. A number of novel androgens have reached clinical testing as potential contraceptive agents; many of these have both androgenic and progestogenic action in a single, modified steroid, thereby holding promise as single-agent contraceptives. Currently, these novel steroids hold promise as both a "male pill" and long-acting injections. Among non-hormonal methods, studies of reversible vaso-occlusive methods (polymers that block transport of sperm through the vas deferens) are ongoing, but reliable reversibility and long-term safety in men have not been established. Proteins involved in sperm maturation and motility are attractive targets, but to date both specificity and biologic redundancy have been challenges for drug development. In this review, we aim to summarize landmark studies on male contraception, highlight the most recent advances and future development in this important field of public health and medicine.

A Cocktail-Inspired Male Birth Control Strategy with Physical/Chemical Dual Contraceptive Effects and Remote Self-Cleared Properties

Inspired by cocktails, we designed a medium term (2-20 weeks) male contraceptive strategy. Through a sequential injection process of four reagents (calcium alginate hydrogel, PEG-Au nanoparticles (PEG-AuNps), EDTA, and PEG-AuNps), physical clogging of the vas deferens and chemical inhibition of the sperm motility were realized simultaneously. The contraceptive period could be directly preset by adjusting the injection ratio of each reagent. More interesting, the embolism area could be readily dredged through a short-time noninvasive near-infrared irradiation. The present study offered an effective and reversible manner to fill the gap of current medium-term contraceptive strategy. In addition, the proposed in vivo pipeline plugging technology, with a flexible noninvasive self-cleared characteristic, might also provide a convenient and reliable strategy for some other biomedical engineering researches.

The future of male contraception: a fertile ground

The continued and rapid expansion of the Earth’s population mandates the need for safe and effective measures of contraception. While a plethora of options exist for women, methods of contraception for the male partner are limited to condoms and vasectomy. The sequela of this discrepancy has led to the family planning burden falling disproportionately on the female partner. For the past several decades, extensive research has been undertaken exploring the feasibility of hormonal male contraception. This proposed method of contraception has focused on suppressing spermatogenesis by exploiting the hypothalamic-pituitary-gonadal (HPG) axis. Beginning with proof of concept studies in the early nineties, administration of testosterone in healthy male subjects has been shown to be an efficacious method of inducing sterility. Owing to ethnic differences in spermatogenesis suppression and the comparatively low rate of azoospermia in Caucasian men with androgen-only regimens, investigators have explored the addition of progestins to further enhance the efficacy of hormonal contraception. Though studies have revealed promise with androgen-progestin regimens, the lack of long-term studies has precluded the development of a marketable product. Recently, more research has been directed towards identifying non-hormonal alternatives to male contraception. These non-hormonal options have ranged from the development of devices facilitating reversible occlusion of the vas deferens lumen to medications disrupting various pathways in the process of spermatogenesis. Underlying the development of hormonal and non-hormonal strategies is the shared enthusiasm men and women have towards these male directed methods. The willingness of couples to pursue these alternatives combined with the global need to reduce the psychological and socioeconomic implications of unintended pregnancy ensures that research will continue to bring this goal to fruition.

Impact of a mild scrotal heating on sperm chromosomal abnormality, acrosin activity and seminal alpha-glucosidase in human fertile males

The aim of this study was to observe sperm aneuploidy, DNA integrity, seminal alpha-glucosidase (NAG) and acrosin activity (AA) under testicular heat stress (SH). Spermatozoa were obtained from 30 healthy adult volunteers subjected to scrotal warming at 43°C for 30-40 min on two successive days per week for 3 months between February 2012 and September 2016. Aniline blue (AB), acridine orange (AO) staining, TUNEL assay and FISH analysis to evaluate sperm function, sperm DNA integrity and chromosomal abnormalities were carried on before, during and after SH. Sperm AA and NAG was measured by microplate reader. The mean parameters of sperm parameters, AA and NAG were significantly decreased. In contrast, the mean percentage of sperm DNA fragmentation and the proportion of aneuploidy of chromosomes 13, 18, 21, X and Y were significantly increased for spermatozoa collected during SH versus before SH (p < .01-.001). After stopping scrotal heating for 3 months, most parameters were completely restored to pre-SH levels. Sperm parameters, sperm DNA integrity, chromosomes, AA and NAG are affected by scrotal exposure to constant SH temperatures several degrees over normal physiological temperature, and after treatment, these parameters were reversibly restored to the level before SH in adult men.

Evaluation of a Zinc Gluconate Neutralized with Arginine Product as a Nonsurgical Method for Sterilization of Rhesus Macaques (Macaca mulatta)

Because rhesus macaques (Macaca mulatta) are prolific breeders, overpopulation can be problematic in both research and feral populations. Currently, the most effective contraceptive methods are hormonal control in female macaques and vasectomies in males. These methods each come with innate challenges, the foremost being the alteration of necessary hormonal patterns. In this study, we assessed the use of zinc gluconate neutralized with arginine as a novel, nonsurgical alternative to male contraception in 12 rhesus macaques. This FDA-approved product for dogs is given as a one-time, intratesticular injection to cause permanent infertility yet theoretically spare the testosterone-producing Leydig cells of the testis. CBC counts, serum biochemistry analyses, testosterone levels, and testicular widths were evaluated at the time of injection and at 1 wk, 1 mo, 2 mo, or 3 mo afterward. Daily postinjection observations revealed transient scrotal enlargement in 8 of the 12 macaques but no indications of pain. In addition, full necropsies including testicular histopathology were assessed at study endpoints. Although some portion of every testis had evidence of seminiferous tubule loss, normal spermatogenesis was present in 22 of the 24 testes. In conclusion, chemical castration with the tested zinc gluconate neutralized with arginine product is not an effective method for sterilization of male rhesus macaques.