In mice, YCT-529 was 99 percent effective in preventing pregnancies within four weeks. In non-human primates, sperm counts fell within two weeks of use.
Published Apr 21, 2025 | 7:00 AM ⚊ Updated Apr 21, 2025 | 7:00 AM
Synopsis: A new male contraceptive pill, YCT-529, has shown promising results in animal trials, proving safe, effective and reversible. Unlike hormonal methods, it works by blocking a protein needed for sperm production without affecting testosterone or causing major side effects. Researchers say it could help share the responsibility for birth control more equally, though it is still several years from being available.
For decades, women have carried most of the responsibility for contraception, with a wide range of options including pills, patches, implants and intrauterine devices (IUDs). Men, by contrast, have had only two main choices: condoms or vasectomy.
That could soon change. A new study published in the journal Communications Medicine reports encouraging results from a non-hormonal male birth control pill called YCT-529.
Designed to be taken orally, the drug was tested in mice and non-human primates. It caused no serious side effects and was found to be reversible, effective, and safe – a potential milestone in contraceptive development.
In male mice, YCT-529 was 99 percent effective in preventing pregnancies within four weeks. In non-human primates, sperm counts fell within two weeks of use.
Unlike earlier male contraceptive attempts that interfered with hormone levels – and often caused side effects such as mood swings, weight gain, or reduced libido – YCT-529 works differently.
It targets a protein receptor known as retinoic acid receptor alpha (RARα), which is essential for sperm production and vitamin A metabolism. Blocking this receptor halts sperm development while leaving other bodily functions intact.
The drug was inspired by animals that were infertile due to genetic loss of RARα but otherwise remained healthy. Scientists aimed to replicate this effect temporarily using medication.
Testosterone levels were unaffected, suggesting users are unlikely to experience common hormonal side effects such as mood changes or loss of libido. Tests also showed no evidence of DNA damage, indicating the drug is neither mutagenic nor carcinogenic.
Another key finding: very little of the drug was present in seminal fluid, reducing the chance of it transferring to a sexual partner – an issue seen with some hormonal methods.
Researchers closely examined the safety profile of YCT-529. In both mice and primates, there were no harmful effects on major organs, no disruption to hormone levels, and no concerning changes in blood tests.
Importantly, the effects were reversible. Mice regained fertility within six weeks of stopping the drug, while primates recovered sperm counts in 10 to 15 weeks. No lasting side effects were observed.
“A safe and effective male pill will provide more options to couples for birth control,” said Gunda Georg, Corresponding Author and Professor at the University of Minnesota’s College of Pharmacy, where the molecule was developed.
“It will allow a more equitable sharing of responsibility for family planning and provide reproductive autonomy for men.”
Nearly half of all pregnancies worldwide are unintended, according to The United Nations Population Fund. While effective options exist for women, men currently have limited alternatives:
This limited choice places a disproportionate burden on women. A safe, effective male pill could help share that responsibility more equally.
YCT-529 may also pave the way for other non-hormonal male contraceptives. If successful, researchers say it could inspire further development of targeted therapies.
Public interest appears strong. Surveys suggest many men would consider using male contraception if it were safe and effective. Many women also support expanding options that do not place the entire burden on them.
YCT-529 is not yet approved for public use. A phase one trial involving healthy male volunteers was completed in 2024 by YourChoice Therapeutics, the biotechnology company developing the drug. A second clinical trial is now under way to assess safety and effectiveness.
“This study laid the groundwork for human clinical trials of YCT-529, which are progressing efficiently,” said Nadja Mannowetz, Lead Author, Chief Science Officer and Co-founder of YourChoice Therapeutics.
“With the unintentional pregnancy rate at nearly 50 percent in the United States and globally, we need more contraceptive options, particularly for men.”
If YCT-529 proves safe and effective in humans and clears regulatory review, it could still be several years before it reaches the market. But researchers remain hopeful.
(Edited by Dese Gowda)
