Aside from condoms and a vasectomy, there aren’t any reliable methods of birth control for men. But researchers at Dana-Farber Cancer Institute and Baylor College of Medicine report in Friday’s edition of the journal Cell that an experimental new drug may point the way to a male birth control pill.
The researchers tested a a small molecule they called JQ1. When they injected mice with JQ1, it reduced their sperm production to the point where the animals became infertile. But while the mice couldn’t sire offspring, JQ1 didn’t interfere with their sex drive — over an 18-month period on the drug, mice produced as much testosterone and mated as much as usual. What’s more, when animals stopped treatment, their fertility was restored in one or two months.
“These findings suggest that a reversible, oral male contraceptive may be possible,” said Dr. James Bradner of the Dana-Farber Cancer Institute and Harvard Medical School, in Boston, in a statement.
How JQ1 works: it’s small enough to cross the blood-testis barrier, so it can reach the cells that make sperm. JQ1 targets a protein called BRDT and inhibits it, thereby preventing sperm from maturing. The result is fewer and lower-quality sperm. Using an initial, lower dose of the drug, four of seven mice that received it were able to reproduce, but their litters were smaller than normal. When the dosage was increased, none of the mice were able to reproduce at all. When the drug was stopped and mice were able to reproduce again, their litters were no different in size, activity or behavior from those of control mice.
The molecule won’t be ready for human testing anytime soon, but the researchers are hopeful for similar results. “Humans do indeed have the BRDT gene, and human genetics suggests a similar role for BRDT in sperm production,” Bradner told HealthDay. “We therefore tested activity against the human BRDT protein and found that JQ1 is a highly potent inhibitor of human BRDT.”
A reversible non-hormonal contraceptive would likely be of much more interest to men than techniques that use hormones — which have wide-ranging and potentially long-term side effects — or other methods using ultrasound or gene-altering effects.