A non-hormonal birth control pill found to be 99 per cent effective at preventing pregnancy in test on mice with no observed side effects. Human trials are being planned, but some researchers warn that safety concerns could yet prevent the drug from making it to the market.

The breakthrough medication could bring balance to the contraceptive burden, with far fewer options available to men.

Until now, Scientists have made various attempts at making an effective and safe male contraceptive but they were based on hormone and none has passed human clinical trials.

With non-hormonal contraceptives, there tends to have fewer side effects, says Dr. Abdullah al Noman of the University of Minnesota in Minneapolis.

“Safety is very important for birth control pills because people are not taking it for a disease, so they are less tolerant of side effects,” says Noman.

He and his colleagues gave male mice a daily dose of a molecule called YCT529 over a four-week period, and found that their sperm count plummeted. Between four and six weeks after the mice stopped receiving the treatment, they could reproduce normally again with no observable side effects.

“When we went to even 100 times higher dose than the effective dose, the compound didn’t show any toxicity,” says Noman, who presented the results today at the American Chemical Society Spring 2022 conference in San Diego, California.

The team tested more than 100 molecules to identify a drug candidate that targets a protein called retinoic acid receptor alpha (RAR-α). Inhibiting this protein blocks the effects of retinoic acid, a derivative of vitamin A that plays an important role in cell development and sperm formation.

The team hopes to begin human clinical trials in the second half of this year.