03:23 19 August 2012
Scientists have discovered a drug which blocks sperm production without lowering the sex drive. The breakthrough brings the world another step closer to create a male equivalent of 'the pill'.
While the female version has been in use for decades, a male version has eluded researchers until now.
An American study published in the journal Cell revealed that a new drug made mice temporarily infertile. Further tests will need to be made on people.
Dr James Bradner, of the Dana-Farber Cancer Institute in Boston, said: "Our findings demonstrate that, when given to rodents, this compound produces a rapid and reversible decrease in sperm count and mobility with profound effects on fertility.
"This compound produces a rapid and reversible decrease in sperm count and motility with profound effects on fertility.
"These findings suggest that a reversible, oral male contraceptive may be possible."
The drug is called JQ1 and targets protein which exists only in the testes and is essential for producing sperm. The drug made the testes of mice shrink and produce fewer - and less mobile - sperm while some were rendered infertile, but when the animals stopped using the drug they were able to have babies.
Researchers also found the pill did not affect testosterone production, mating behaviour, or the health of offspring conceived. Another important attribute of the drug was that sperm production went back to normal when its usage was discontinued.
Dr Allan Pacey, senior lecturer in andrology at the University of Sheffield, told the BBC: "To date, most of the trials have attempted to stop sperm production by manipulating the male hormone testosterone through the use of injections or implants.
"These approaches work reasonably well, but none have yet made it to routine use. So the door is wide open for someone to develop a novel drug that doesn't rely on hormones."
It is believed that this drug will be relatively easy to test on humans.
Bradner continued: "While we will be conducting more research to see if we can build on our current findings, JQ1 shows initial promise as a lead compound for male contraception."