For dudes who like to notch their belts or track miscellaneous pants-related data, the fact that men produce 1,500 sperm every second seems impressive. But that comes at a cost: babies. Women can choose among a wide variety of birth control methods, but options for men are limited to slip-ons or snips. For now. A couple of seminal approaches to getting the little swimmers to simmer down may soon start to trickle out of the laboratory. Here are two of the headiest prospects for choking off male fertility.

H2-gamendazole ————–

Molecular Formula: C 18 H 12 C l2 F 3 N 2 O 2 Na + 1/3 H 2 O

Research Stage: Animal testing

How it Works: Keeps sperm from reaching maturity

H2-gamendazole makes sperm go off half-cocked. Normally, premature sperm cells grow a tail and head in the testis, but H2-gamendazole keeps them from reaching this stage of development. The unfinished sperm fragments are then reabsorbed into the testis, never ending up in the semen. “If there's no sperm, the egg's not going to get fertilized,” says Joseph Tash, a reproductive biologist at the University of Kansas Medical Center, who has worked on the compound since 2001. Almost two years ago, the FDA reviewed the compound, and now the agency wants Tash to investigate any crossover effects on the female body. That's because it's still unclear if the compound remains in the semen and whether that would harm a woman if it ends up in the vagina.

JQ1 —

Molecular Formula: C 23 H 25 CIN 4 O 2 S

Research Stage: Chemical optimization

How it Works: Tricks the body into forgetting how to make sperm

Like many children, the JQ1 molecule is a “happy accident.” Jay Bradner and his team at Harvard's Dana-Farber Cancer Institute had been working on blocking bromodomain proteins, which he describes as “Post-it notes that cells place around the genome to remind them of their identity.” JQ1 blocked a bromodomain in cancer cells, causing them to forget how to be cancer. Great. But JQ1 also obstructed a testicle-specific bromodomain called BRDT, making the sex cells that would otherwise produce sperm draw a blank about their own behavior—mice treated with JQ1 can hump with abandon yet generate zero mouselings. But it will be at least several years before the drug is available: Researchers need to find a version of the molecule that works on the testicle protein only, to avoid any weird side effects.