A birth control pill for men is in sight, according to a team of American researchers.
The scientists presented a report on a non-hormonal male contraceptive that effectively prevented pregnancy in mice without obvious side effects.
They found that, when given orally to male mice for four weeks, the compound dramatically reduced sperm counts and was 99% effective in preventing pregnancy.
This would put the contraceptive medication for men on par with the pill for women, which has been available on the NHS for just over 60 years.
Presenting the work at the American Chemical Society (ACS) spring meeting, Md Abdullah Al Noman said: "Scientists have been trying for decades to develop an effective male oral contraceptive, but there are still no approved pills on the market."
He added that most compounds currently undergoing clinical trials target the male sex hormone testosterone, which could lead to side effects such as weight gain, depression and increased low-density lipoprotein (known as LDL) cholesterol levels.
“We wanted to develop a non-hormonal male contraceptive to avoid these side effects,” says Noman, a graduate student at the University of Minnesota.
To develop their non-hormonal male contraceptive, the researchers targeted 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, differentiation (including sperm formation) and embryonic development.
Knocking out the RAR-α gene in male mice makes them sterile, without any obvious side effects.
Other scientists have developed an oral compound that inhibits all three members of the RAR family and causes reversible sterility in male mice, but the team wanted to find a drug that was specific for RAR-α and therefore less likely to cause side effects.
They identified a compound, which was named YCT529, that when given orally to male mice for four weeks, dramatically reduced sperm counts and was 99% effective in preventing pregnancy without any observable side effects.
The mice could father pups again 4-6 weeks after they stopped receiving the compound.
Professor Gunda Georg said that YCT529 will begin testing in human clinical trials in the third or fourth quarter of 2022.
“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,” she said.
