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New Oral Male Contraceptive Is 99 Percent Effective In Preventing Pregnancy In Mice


Tom Hale

Tom is a writer in London with a Master's degree in Journalism whose editorial work covers anything from health and the environment to technology and archaeology.

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Recent years have seen an array of new research exploring possible male contraceptives - and this one looks especially promising. Image credit: SciePro/

Could a male contraceptive pill finally be on the horizon? Yet another early study suggests so. In a new research project, a new non-hormonal male contraceptive pill has been found to highly effectively prevent pregnancy in mice with zero obvious side effects. 

Presenting their breakthrough at the spring meeting of the American Chemical Society (ACS), scientists from the University of Minnesota say they have found a compound that could potentially pave the way for a birth control option for men similar to the widely taken hormonal pill for women. However, they note that there's still a long way to go before this treatment can even be considered for pharmacy shelves. 


The non-hormonal male contraceptive works by targeting a protein called the retinoic acid receptor alpha (RAR-α). This protein is one of a family of three nuclear receptors that bind retinoic acid, a form of vitamin A that plays important roles in cell growth and the process of sperm formation. 

Previous attempts to find a viable male contraceptive have used the power of all three members of the RAR family (RAR-α, -β and -γ), but this latest effort wanted to find a drug that was specific for RAR-α, believing it could lead to fewer unwanted side effects. 

To find this compound, the researchers designed and synthesized almost 100 compounds and looked at their ability to bind to, and thereby inhibit, RAR-α. One compound did the trick — YCT529 that inhibited RAR-α almost 500 times more potently than it did RAR-β and -γ.

When male mice were given an oral dose of YCT529 for four weeks, YCT529 dramatically dropped sperm counts and proved to be 99 percent effective in preventing pregnancy without any observable side effects. Most importantly, it appears to be totally reversible; the mice could father pups again four to six weeks after they stopped receiving the compound.


The team hopes to start human clinical trials of YCT529 by the end of 2022. While things are looking good so far, they are also looking out for other promising compounds. 

“Because it can be difficult to predict if a compound that looks good in animal studies will also pan out in human trials, we’re currently exploring other compounds, as well,” Professor Gunda Georg, a medicinal chemist at the University of Minnesota, said in a statement.

As it stands, women have access to a wide choice of birth control, from pills to patches to intrauterine devices, meaning they bear most of the burden of the responsibility of contraception. Sexism has undoubtedly been a factor in this lack of progress of a safe and reversible male contraceptive, but there have been some significant scientific hurdles to overcome too.

Recent years, however, have seen plenty of new research exploring possible male contraceptives, from pills and rub-in gels to injections, switches, and even magnets. It may still be a few years before they are a reality, but it certainly seems like the momentum of a viable male contraceptive is growing. 


Importantly, there seems to be a market for it too, something that is vital for research to actually make it from the lab to securing funding and into production. According to a 2019 YouGov poll in the UK, 33 percent of sexually active men said they would consider taking a male version of the pill; exactly the same percentage of women who currently use hormonal contraception.


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