More than 100 million women worldwide use a contraceptive pill. Now, with the development of the first drug to offer non-hormonal and reversible male birth control, men are a step closer to something similar. And it doesn’t seem to affect sex drive, either — at least not in mice.
A non-hormonal option for male contraception would be preferable to the hormonal treatments currently in clinical trials, because the types of hormones that make men infertile, thus providing birth control, have more severe side effects than those used in the female pill. The hormones can affect bone formation and cause liver abnormalities.
“Non-hormonal targets are urgently needed,” says James Bradner, a physician at the Dana-Farber Cancer Institute in Boston. He and his colleagues have developed a drug called JQ1, which inhibits a testes-specific protein called BRDT that is essential for fertility.
All sperm cells develop from germ cells. Early in this process, BRDT enters the nucleus and switches on relevant parts of the genome that instruct the cell to mature into a sperm cell. JQ1 binds to BRDT at exactly the same part of the protein that sticks to the genome, preventing it from giving instructions to the cell.
When mice were administered daily injections of two different doses of JQ1 over a three- or six-week period, they saw at least a 90 percent decrease in sperm count and at least a 75 percent decrease in sperm cell motility. The decrease in the sperm count was so substantial at the higher dose that all of the mice became infertile. Importantly, though, within a month or two of stopping the drug treatment, mouse fertility was completely restored.
No significant side effects occurred, and testosterone levels appeared normal. Mating behaviors were also unaffected. “There was no obvious effect on the mojo of the animals,” Bradner says.