More than 100 million women worldwide use a contraceptive pill. Now men are a step closer to protecting themselves in a similar way with the development of the first ever drug to offer non-hormonal and reversible male birth control. And as an added bonus, it doesn’t seem to affect sex drive either – at least in mice.
A non-hormonal option for male contraception is preferable to hormonal treatments currently in clinical trials, because the types of hormones that make men infertile have more severe side effects than those used in the female pill. The hormones can affect bone formation and liver abnormalities.
“Non-hormonal targets are urgently needed,” says James Bradner, a physician at the Dana-Farber Cancer Institute in Boston, Massachusetts. Now, 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. At an early stage of 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. “It’s like removing the Post-it note that reminds the cell to turn into a sperm cell,” says Bradner.
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 per cent decrease in sperm count and at least a 75 per cent 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.