Science is moving closer to a male contraceptive pill, and human clinical trials of a non-hormonal version could begin later this year, researchers say.
The experimental contraceptive works in mice, according to a preliminary study scheduled for presentation Wednesday at an American Chemical Society (ACS) meeting in San Diego.
"Scientists have been trying for decades to develop an effective male oral contraceptive, but there are still no approved pills on the market," said researcher Md Abdullah Al Noman, a graduate student in the lab of Gunda Georg at the University of Minnesota.
Currently, there are only two proven birth control choices for men — condoms and vasectomy. Condoms can fail and vasectomy is a surgical procedure that can be expensive and difficult to reverse, the study authors noted.
Most male birth control pills currently in clinical trials target the male sex hormone testosterone. This could cause harmful side effects such as weight gain, depression and higher levels of LDL ("bad") cholesterol.
"We wanted to develop a non-hormonal male contraceptive to avoid these side effects," Noman said in an ACS news release.
The researchers found that a compound called YCT529 is highly effective at knocking out a protein called retinoic acid receptor alpha (RAR-α). This protein plays an important role in sperm formation, embryonic development and cell growth.
When given orally to male mice for four weeks, YCT529 significantly reduced sperm counts and was 99% effective in preventing pregnancy, without causing any detectable side effects, the researchers reported.
The male mice could father pups again four to six weeks after they stopped receiving the compound, according to the study.
YCT529 will begin testing in human clinical trials in the third or fourth quarter of 2022, according to Georg.
"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 in the news release.
Data and conclusions presented at meetings should be considered preliminary until published in a peer-reviewed medical journal.