For years, the science of male contraception focused on hormone therapy (or, of course, wearing a condom). But new research suggests that targeting a very particular protein in sperm—rather than trying to clamp down on male hormones—may pave the way to a new male contraceptive.

Researchers at Osaka University in Japan discovered that genetically engineering mice without the ability to produce the key protein calcineurin made the mice infertile, as their sperm were unable to swim efficiently enough to penetrate the female’s egg, according their study results published in Science.

9 Problems You’re Having With Your Penis and What to Do About Them >>>

During an additional study, fertile mice were given doses of cyclosporine A and FK506 in order to block calcineurin. In less than a week, their sperm underwent defects that caused them to become infertile. Within a week of discontinuing drug intake, however, the mice became fertile again.

Since calcineurin is also found in human sperm, researchers believe the protein may potenitally be a new target for male contraceptives in humans.

A small study of men who used cyclosporine A after an organ transplant found that three out of four men were able to reproduce successfully. Other studies have shown no effects against sperm movement.

10 Dumb Mistakes That Can Get Her Pregnant >>>

Some existing male contraceptives focusing solely on hormones have been tied to a lower sex-drive, making them an unlikely choice for men.

Patricia Morris, the director of biomedical research at the Population Council, says that “we certainly need male contraceptives, and new designs that aren’t hormone-based are really welcomed in terms of acceptability.”

Since there’s no telling when these contraceptives will be ready for the market, remember that there are plenty of alternatives to consider while you wait.

How Much Sex is Too Much Sex? >>>