Contraception has been solely the responsibility of women. Over 20 types of contraception have been developed, but the only methods available to men have been condoms and vasectomy. This situation is expected to change. A new method of male contraceptive that suppresses sperm motility has proven its safety in clinical trials in the United States, increasing the prospects for commercialization.
YourChoice Therapeutics, a U.S. biotechnology corporation, announced on the 22nd (local time) in the international journal Communications Medicine that it has confirmed the safety of the non-hormonal oral contraceptive 'YCT-529' in Phase 1 clinical trials. YCT-529 is a non-hormonal agent that blocks the binding of vitamin A metabolites that induce sperm production to testicular receptors, preventing the sperm production process.
Various male contraceptives have been developed thus far, but most operated by regulating sex hormones to inhibit sperm production, similar to female contraceptives. As a result, issues such as decreased libido and depression became significant side effects, leading to a lack of success. In contrast, the new drug is not hormone-based, resulting in fewer side effects, and the company noted that reproductive function can be quickly restored after discontinuation.
◇ Blocking sperm production, no hormonal side effects
The aim of this clinical trial was to confirm the safety of the drug and its bioavailability rather than the contraceptive effect of reducing sperm count. Stephanie Page, an endocrinology professor at the University of Washington, evaluated that "given the previous focus solely on hormone-based contraceptives, the mere fact that a non-hormonal contraceptive is safe for humans is a significant advancement."
The clinical trial included 16 healthy adult men aged 32 to 59 who had already undergone vasectomy, making them infertile. Participants were divided into two groups and took YCT-529 in different dosages twice. One group increased from 10 mg to 30 mg, while the other group increased from 90 mg to 180 mg, and some took an additional 30 mg after a high-fat, high-calorie meal to examine the effect of food on drug absorption.
Trial results indicated that the drug was not rapidly broken down in the participants' bodies and blood levels were maintained, with an average half-life reached over 2 to 3 days. Nadja Mannowetz, Chief Scientific Officer at YourChoice, stated, "It may be sufficient to take one pill a day," and noted, "The final dosage for market release is likely to be around 180 mg."
No significant side effects were observed in the participants. The company explained that since this method does not touch the hormonal system, the risk of side effects such as those concerning sexual function, libido, and mood changes, which had been a concern with existing male hormonal contraceptives, is reduced. However, Professor Page pointed out, "All drugs can have side effects, and this clinical trial was small, so a larger-scale trial is needed in the future."
Male contraceptives that block sperm production itself, like YCT-529, take about three months to show effects after taking them. This is due to the time it takes for sperm to mature. If discontinued, sperm production resumes after about three months.
Previously, in animal experiments conducted in March by a joint research team from the University of Minnesota's College of Pharmacy, Columbia University, and YourChoice, the contraceptive effect of YCT-529 was also confirmed. When YCT-529 was administered to male mice, it prevented pregnancy by 99% after four weeks, and when administered to male primates, there was a significant reduction in sperm count within two weeks.
In both animal models, reproductive function was completely restored after discontinuation of the drug. In mice, sperm counts returned to normal levels within six weeks, while in primates, it took 10 to 15 weeks. No drug-related side effects were observed.
◇ Gel contraceptive that blocks sperm movement also under development
In addition to YCT-529, candidate substances for male contraceptives that regulate hormones are also being developed. A representative example is the hormone-conjugated gel 'NES/T' being developed by the National Institute of Child Health and Human Development (NICHD) in the United States. It works by absorbing the female hormone progestin compound nestorone and the male hormone testosterone through the skin to inhibit sperm production through the brain. It has recently completed Phase 2 trials and is preparing for Phase 3.
U.S. biotechnology corporation Contraline is conducting Phase 1 clinical trials for the vas deferens-injected contraceptive material 'Adam,' which can replace condoms and vasectomy. Adam works by injecting a water-soluble hydrogel into the vas deferens to block sperm movement. The hydrogel contains a high amount of water, making it a soft material like pudding or jelly. Additionally, hormone-based oral contraceptives are also under development.
There is also a high demand for male contraceptives. According to a study released in 2023, about 75% of over 2,000 men in the United States and Canada expressed willingness to try new contraceptive methods. In a previous 2019 survey, about half of men aged 18 to 49 who did not want to become pregnant responded that they were "very interested."
Professor Page noted, "Men also want more contraceptive options and are prepared to participate actively," adding that "these efforts will grant greater reproductive autonomy to both couples and individuals."
References
Communications Medicine (2025), DOI: https://doi.org/10.1038/s43856-025-01004-4
Communications Medicine (2025), DOI:
https://doi.org/10.1038/s43856-025-00752-7