Science just got closer to developing a birth control pill for men letting women everywhere sigh in relief as the burden of pregnancy prevention may soon lessen. The breakthrough comes after a group of Japanese researchers studied the effects of drugs given to organ transplant patients on mice.

The study, published in Science was led by Haruhiko Miyata of Osaka University's Research Institute for Microbial Diseases, saw the effects of Cyclosporine A and tacrolimus on mouse sperm. Cyclosporine A and tacrolimus are given to patients because of their immunosuppressant function, which prevent the body from producing proteins—like an enzyme called calcineurin—that would lead the body to reject the “new” organ. 

Researchers found a kind of calcineurin only found in sperm and studied it in the mice. Long story short, researchers found mice were basically infertile without calcineurin because they couldn’t impregnate females on account of their sperm was too weak. Scientists saw it only took a few days for each of the drugs to make the mice infertile and after one week of not taking the drugs the mice became fertile again.  

The study concluded, “Considering these results in mice, sperm calcineurin may be a target for reversible and rapidly acting human male contraceptives.” 

[via LA Times]