The pill revolutionized attitudes toward sex when it was introduced in 1960, but its side effects left much to be desired. Women were stuck with the worst part of the birth control deal — an increased risk of stroke, acne, nausea, and a freewheeling hormonal rollercoaster — while men happily reaped the benefits. But a new study from the University of Virginia has just brought us one step closer to the next great contraceptive revolution. And this time around, The Pill is going to be for men.

As researchers at the University of Virginia describe in a study in Protein Expression and Purification today, they’ve just made a discovery that could help stop sperm from swimming to female eggs — and there aren’t any mood-shifting, stroke-inducing hormones involved. The trick to male contraception, it seems, is thwarting the activity of an enzyme known as TSSK2, found only in testicles, lead author John Herr, Ph.D. explains to Inverse.

By blocking an enzyme involved in making sperm mobile, it's hoped that the resulting sluggish swimmers won't be able to reach the egg.

The enzyme is involved in creating sperm that are mobile, so Herr and his team are hoping that blocking it will result in more sluggish swimmers. More crucially, the enzyme is only involved at the very last stage of sperm production; halting its function, therefore, is less likely to have effects anywhere else in the body.

The research team’s big discovery was a way to produce that enzyme en masse — making it infinitely easier to screen drugs meant to block it.

They’re hoping that, in the future, those massive rounds of drug testing will help identify a drug that binds only to the sperm-specific form of the enzyme. Herr’s goal throughout this process, as he explained, is to avoid using a drug that has effects anywhere else in the body, so as not to repeat the mistakes of the pill.

Herr, who previously developed a men’s home fertility test called SpermCheck, called his team’s discovery a “milestone,” though he’s aware there’s a lot more work required before men will be popping sperm-slowing pills.

“More refinement of lead small molecule inhibitors is underway,” he says.

In the meantime, an injectable male birth control drug called Vasalgel could be hitting the contraceptive market as soon as 2018. Unlike Herr’s approach, Vasalgel prevents sperm from swimming out into the eggy wild altogether by way of a physical roadblock, delivering the drug through an injection in the vas deferens — that’s the highway between the testicles and urethra — that blocks sperm from exiting so they’re eventually reabsorbed back in the body.

It’ll take some time before either of these male birth control measures materialize, but at the very least they are reopening up the contraceptive conversation to include men.

Whether that conversation will be a welcome one remains to be seen.

Photos via John Herr, Ph.D.