Scientists said they had developed a male contraceptive that was 99% effective in mice and did not cause noticeable side effects, and the drug is expected to enter human trials by the end of this year.

The findings will be presented at the American Chemical Society’s spring meeting, and represent a major step toward expanding birth control options — as well as responsibilities — for men.

Since the contraceptive pill was first approved in the 1960s, researchers have been interested in their male equivalent, MD Abdullah Noman, a graduate student at the University of Minnesota who will present the work, told AFP: “Multiple studies have shown that men are interested in taking part. responsibility for birth control with their partners” — but so far, there have only been two effective options available: condoms or vasectomy.

Vasectomy reversal surgery is expensive and not always successful.

Female birth control pills use hormones to disrupt the menstrual cycle, and historical efforts to develop a male equivalent have targeted the male hormone testosterone.

But the problem with this approach is that it causes side effects such as weight gain, depression and increased levels of cholesterol known as LDL, which increases the risk of heart disease.

The female contraceptive pill also carries side effects, including blood clotting risks — but because women face pregnancy in the absence of contraception, the risk calculation varies.

To develop a non-hormonal drug, Neumann, who works in Professor Gonda George’s lab, targeted a protein called the RAR-alpha retinoic acid receptor. Within the body, vitamin A is converted into various forms, including retinoic acid, which plays important roles in cell growth, spermatogenesis and fetal development.

Retinoic acid needs to interact with RAR-alpha to perform these functions, and laboratory experiments have shown that mice without the RAR-alpha gene are sterile.

For their work, Neumann and George developed a compound that blocks the action of RAR-alpha. They identified the best molecular structure with the help of a computer model.

“If we know what the keyhole looks like, we can make a better key – that’s where the computational model comes in,” Neumann said.

The special chemical, known as YCT529, is designed to interact specifically with RAR-alpha, and not two other RAR-beta and RAR-gamma-related receptors, in order to reduce potential side effects.

When administered orally to male mice for four weeks, YCT529 significantly reduced sperm count and was 99% effective at preventing pregnancy in a mating experiment.

The researchers monitored weight, appetite and general activity, and found no apparent negative effects, although of course mice cannot report side effects such as headaches or mood changes.

Gonda George said the team, which received funding from the National Institutes of Health and the Male Contraceptive Initiative, is working with a company called YourChoice Therapeutics to begin human trials by the third or fourth quarter of 2022.

“I’m optimistic this will move forward quickly,” she said, imagining a possible timeline for marketing in five years or less.

“There is no guarantee that it will work, but I would be really surprised if we don’t see an effect on humans as well,” she added.