Biochemists at the Baylor College of Medicine and Harvard Medical School have isolated a molecule that could lead to a male birth control pill.

A study led by Dr. Martin Matzuk, director of the Center for Drug Discovery at Baylor, and Dr. James Bradner, assistant professor at Harvard Medical School, found that the molecule, called JQ1, inhibited the amount and quality of sperm produced by male mice. Their study was published this week in the journal Cell.

“We found that the JQ1 molecule causes a contraceptive effect in males,” said Matzuk. “If you stop the drug, there’s complete reversibility.”

The investigation into JQ1 actually began when Bradner began researching it as a possible cancer treatment. Since JQ1 is an inhibitor of a specific bromodomain proteins, Bradner contacted Matzuk to ask if JQ1 would have any effect on BRDT, a bromodomain protein involved in the process of sperm generation.

The scientists found that JQ1 did indeed block the normal process of sperm production. The molecule was also able to breach the blood-testis barrier, which is the barrier between blood vessels and the seminiferous tubules where sperm is produced. The male mice in the study mated normally, but were sterile, as the amount and quality of their sperm was low. Small molecules such as JQ1 can be used in pills similar to those used for female contraceptives.

Though Matzuk believes this research will help pave the way for a male birth control pill, he admits that JQ1 will not be the molecule used in future contraceptives. “JQ1 is not the pill for men, because it also binds other members of the bromodomain family,” Matzuk said. “However, the data is proof of principle that BRDT is an excellent target for male contraception and provides us with useful information for future drug development.”