MELBOURNE - A contraceptive pill for men is a step closer to reality following a discovery by US scientists.
Researchers found a compound called JQ1 disrupts the development of sperm, decreasing sperm count and mobility.
But in a crucial finding, the effects of JQ1 are reversible.
Mice given the drug became infertile but when treatment stopped, sperm production returned to normal and healthy offspring were conceived afterwards.
There was also no impact on testosterone production or sex drive.
The study, published in the journal Cell, concluded that although the drug had been tested in mice it would probably work in humans due to reproductive similarities.
"These findings suggest that a reversible, oral male contraceptive may be possible," said study author Dr James Bradner from the Dana-Farber Cancer Institute in Boston.
Australian male fertility expert Professor Robert McLachlan said the researchers had targeted a factor in DNA remodelling that was essential for sperm production, blocking the cell division necessary to produce normal sperm.
However, he said lengthy research would be needed in animals before it could even begin tests in humans.