Researchers in Japan say men might soon get a birth control pill of their own.
The scientists claim that the drugs cyclosporine A (also known as CsA) and FK506 (also known as tacrolimus) could be the key to the creation of a male oral contraceptive. Both drugs are given to transplant patients to prevent their bodies from rejecting their new organs. They work by preventing the immune system from making a protein that would otherwise mobilize the T-cells to attack, targeting the enzyme calcineurin. 
Other male birth control research has focused on lowering sperm count, but the new drug actually targets sperm function and makes them unable to fertilize an egg.
Researchers discovered that a particular version of calcineruin was found only in sperm cells, prompting the investigators to study the drug’s possible effect on male fertility in animals. They genetically altered “knockout” mice to render them unable to produce PPP3CC, the protein found specifically in the sperm version of calcineurin, using CsA and FK506. Poor mice. 
In “knockout” mice, the lack of PPP3CC was found to make it more difficult for sperm to move around inside of the females. The part of the knockout mice’s sperm which connected the head to the tail was more rigid than that of normal mice, resulting in “hyperactivation” – a particular type of movement that requires the sperm’s tail to propel it towards an egg.
The sperm never penetrated the egg, thus fertilization never occurred.
When the researchers gave the immunodeficiency drugs to regular mice, all of the animals produced the same rigid sperm as the genetically altered mice, though it took 2 weeks for the drugs to affect the mice’s sperm.
Just one week after scientists stopped giving the drugs to the mice, their sperm reportedly returned to normal. So, not only might the drugs be used to create male birth control pills, researchers believe that the contraceptive would be wholly reversible.
“Considering these results in mice, sperm calcineurin may be a target for reversible and rapidly acting human male contraceptives,” they concluded.
The next step is for researchers to test CsA and FK506 on humans to make sure they use the drugs to prevent pregnancy, but also reverse the effect once the medications are stopped. Though just like female birth control, I’m sure the new drug will not come without its share of adverse effects (though it would be a non-hormonal medication).
“Considering these results in mice, sperm calcineurin may be a target for reversible and rapidly acting human male contraceptives,” the researchers concluded.
The study was recently published in the journal Science.
 Medical Daily