A contraceptive for men that showed efficacy in mice will begin to be tested in humans

A contraceptive pill for men is nearing its human testing phase after 99% effective results were reported in mouse trials.

The American scientists behind this breakthrough belong to the University of Minnesota and presented the results of their research at the Spring 2022 conference of the American Chemical Society in San Diego, California, this Tuesday.

According to them, the secret of this pill is that testosterone, the male sex hormone, is not digested, which reduces the risk of side effects that have so far prevented drugs other than condom from reaching pharmacies as contraceptive methods for men.

“Most female birth control pills work with female sex hormones,” said Abdullah al Noman, one of the researchers, noting the lack of approved male oral contraceptives on the market.

“But targeting the male sex hormone leads to many side effects, such as weight gain, depression and increased risk of cardiovascular disease,” he said. “Men are less willing to take a birth control pill that has significant side effects. That's why we're targeting a non-hormonal path to developing a male birth control pill.”

It should be noted that female hormonal contraceptives also cause many side effects, but these have not been an impediment to their being sold freely in pharmaceutical companies and their medical use is often recommended as a method of family planning.

Although progress has been made on non-hormonal oral contraceptives for women, there are currently no such products on the market or conclusive studies to support them.

For men, this non-hormonal contraceptive works as an inhibitor of a protein called retinoic acid alpha receptor (RAR-α), one of a family of three nuclear receptors that bind to retinoic acid, a form of vitamin A that plays an important role in sperm formation, among other things.

What the researchers found was that eliminating the RAR-α gene in male mice became infertile.

Although another study had formulated an oral compound that inhibits all three nuclear receptors, the team at the University of Minnesota wanted to produce a drug specific for RAR-α to minimize side effects.

The researchers, led by Dr. Gunda Georg, found that a compound called YCT529 could inhibit RAR-α alone. The researchers then administered YCT529 orally to male mice over a four-week period and found that it dramatically reduced sperm count and prevented pregnancy by 99 percent without causing any observable side effects.

Basically, male mice became fertile again four to six weeks after they stopped taking YCT529.

“That is very important: that you eliminate the target (RAR-α), that you have achieved the desired effect but that the mice are also viable and healthy,” Georg said. “Of course, you have to be careful with this analysis because they are mice and not humans, but, nevertheless, the effect was very, very promising.”

The next question, of course, is whether the pill will work in humans without causing side effects. Human clinical trials may begin in the second half of the year, Georg said.

The company YourChoice Therapeutics, which now holds the license for the candidate drug, is preparing documentation and application for approval from the U.S. Food and Drug Administration, a prerequisite for clinical trials.

Because there is no way to guarantee that a drug that works well in animals is as safe and effective in humans, Georg said his team continues to explore other compounds that could lead to a viable male contraceptive pill.

With no oral contraceptive options available, men so far only have condoms and vasectomies to choose from to prevent pregnancy.

Condoms, the researchers noted, are single-use and prone to failure, while vasectomies, a surgery to cut the vas deferens that allow sperm to travel from the testicles to the penis, are considered permanent, although they are not necessarily permanent, while reversal surgeries are costly and are not guaranteed to work.

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