Japanese researchers may have discovered the formula for male birth control pills.
Cyclosporine A and FK506 are drugs usually given to organ transplant recipients in order to prevent their bodies from rejecting the new organs.
Researchers previously found the drugs suppress the development and motility of sperm by inhibiting an enzyme called calcineurin, The Daily Beast reports.
A team at Osaka University's Research Institute for Microbial Diseases was curious whether targeting two proteins, PPP3CC and PPP3R2, in calcineurin could serve as a contraceptive for mice.
So, the researchers engineered male mice that made less PPP3R2 and were unable to make PPP3CC, according to the Los Angeles Times.
Female mice had sex with the male mice, known as "knockout" mice, and did not become pregnant.
After a series of tests, the team found the sperm created by the "knockout" mice could not penetrate the zona pellucida, the membrane surrounding the female egg.
This was because the sperm cells of the knockout mice were not able to wag their tails as powerfully (because they weren't as flexible) as normal sperm.
The next step was to give cyclosporine A and FK506 to normal mice since the drugs inhibit the enzyme containing PPP3CC and PPP3R2.
Those mice that received either of the drugs became infertile for two weeks and became fertile again a week after stopping the treatment. Cyclosporine A took five days to work while FK506 needed just four.
In the study, the team wrote,
Considering these results in mice, sperm calcineurin may be a target for reversible and rapidly acting human male contraceptives.
Aspiring users of male contraception should be grateful for these findings because the male birth control method that's gained the most traction so far is Vasalgel, which is administered via an injection to the vas deferens.
The potential pill, however, would be non-invasive and non-hormonal. Female birth control, on the other hand, can come with numerous side effects, a great deal of which stem from the pill's impact on hormones.
Apparently, the only thing that would be affected by the potential pill for men would be sperm.