For decades, you’ve heard about the pill — for women. The weight of contraception fell disproportionately on women, but what if we could flip the script? A revolutionary new drug called YCT-529 could soon give men a convenient, reversible way to take control of birth control. And if the latest studies in mice and monkeys are any indication, that future is almost here.

Nearly half of all pregnancies are unintended. Women bear the brunt of contraceptive responsibility — with pills, IUDs, implants, patches, and more. Meanwhile, men are stuck with just two real choices: condoms or vasectomy. The former is prone to user error. The latter is usually permanent and invasive.

Efforts to develop male contraceptives have been underway for years. Hormonal methods using testosterone showed promise but also triggered side effects like mood swings, weight gain, and decreased libido. None really made it to market.

But this new drug is different. YCT-529 is a first-in-class, hormone-free and orally administered male contraceptive. The key lies in vitamin A. Specifically, in a protein that helps convert it into a hormone-like signal in the testes. That signal is essential for sperm development. Block it, and the body can’t produce viable sperm.

“A safe and effective male pill will provide more options to couples for birth control,” said Gunda Georg, the corresponding author of the study and a professor in the College of Pharmacy where the drug molecule was developed. “It will allow a more equitable sharing of responsibility for family planning and provide reproductive autonomy for men.”

For now, the pill has only been proven in animal trials — but it worked astonishingly well.

Prevented 99% of pregnancies

In mice, YCT-529 rendered 99% of males temporarily infertile after just four weeks of daily oral dosing. Even more exciting? Fertility returned within six to twelve weeks after stopping the drug.

In non-human primates — Cynomolgus macaques, a common stand-in for humans — the drug suppressed sperm counts below fertility thresholds within just two to five weeks. After treatment stopped, every animal recovered normal sperm counts and testicular function in two to three months. No animals showed toxic reactions or damage to their testes.

The results in primates have paved the way for human clinical trials. YourChoice Therapeutics, the startup behind YCT-529, is now preparing to test the pill in men.

“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% in the U.S. and globally, we need more contraceptive options, particularly for men.”

If human trials show similar results — reversible infertility without side effects — the implications could be enormous.

Balancing the Scales

For starters, it could prevent millions of unwanted pregnancies, with virtually no side effects. Sure, skeptics will doubt whether men would even take such a pill. But a global poll from 2022 found that over 50% would. Men tend to dislike condoms and they dislike vasectomies even more; having access to reliable, safe contraception could be a boon for many men.

The science is extremely exciting. The social changes it could bring are just as important. For generations, reproductive responsibility has been placed squarely on women. The arrival of a reliable male contraceptive could rebalance the equation. The idea of shared responsibility in birth control isn’t just fair — it’s overdue.

Of course, this all hinges on whether this actually works in humans. The team is confident. The macaque test, in particular, provides really good evidence to suggest that the drug would be efficacious and reversible in humans. The fact that it’s all in a pill without any hormonal effect is even more encouraging.

“A potential male contraceptive that is administered orally would be the best-case scenario for ease of use and compliance,” the researchers conclude.

The study has been published in Nature Communications Medicine.