Ever wonder why there’s no birth control pill for men? For starters, it’s a math problem: To stop a woman from getting pregnant, all you have to do is block a single egg each month. But a man produces millions of sperm each day — about 1,000 every time his heart beats. Blocking them all is a much bigger task.
This helps explain why no one has come up with a reversible form of birth control for men since the condom was introduced centuries ago. (The first unambiguous description of the prophylactic’s use appears in a 1564 writing called “De Morbo Gallico,” which describes a syphilis outbreak in Europe that began in France in the 1490s.)
But a new option may now be on the horizon. A study published in a recent edition of the journal Cell describes an experimental drug that, when taken daily by male mice, reduced their sperm count so much that the animals were rendered effectively infertile. When the drug was stopped, sperm counts and quality were restored and the mice were able to sire healthy offspring.
The drug is a small molecule that the researchers have dubbed JQ1. Due to its small size, it is able to cross the blood-testis barrier and reach the cells where sperm are produced. Once in place, JQ1 appears to bind with a protein called BRDT, disrupting its normal function and ultimately preventing sperm cells from maturing.
A 2007 study found that messing with the BRDT protein in mice caused the animals to become sterile. Another study from 2010 showed that JQ1 and other small molecules could target proteins like BRDT. So an international team of researchers led by Dr. Martin Matzuk of Baylor College of Medicine in Houston put it all together and confirmed that JQ1 reduced sperm production.
When seven male mice were given a daily dose of 50 milligrams of JQ1 per kilogram of body weight, only four of them were able to sire offspring, and the litters were smaller than usual. When the daily dose was doubled, none of these four mice were able to reproduce at all.