Male pill moves a step closer as scientists work out how to stop sperm from swimming
Scientists have made a breakthrough which could be key to developing a male contraceptive pill.
The discovery uses a peptide which changes the way human cells work, 'switching off' sperm's ability to swim, to render men temporarily infertile.
Scientists hailed the results as "startling - and almost instant". It raises the prospect of a fast-acting pill or a nasal spray a man could take hours or even minutes before sex.
Women are typically advised to stop taking the Pill weeks or even months before trying to conceive.
But researchers believe the effects of a male pill would happen almost instantly, and wear off within a matter of days.
Family planning experts said a reversible male contraceptive could help men control their fertility, and benefit couples where the woman does not want to take the Pill.
Lead researcher Professor John Howl, of Wolverhampton University, said the new compound, made in the lab, had shown immediate results.
"The results are startling - and almost instant. When you take healthy sperm and add our compound, within a few minutes the sperm basically cannot move," he said.
Working with scientists from Portugal, the team made a compound called a cell-penetrating peptide.
"This is a totally unique approach," Prof Howl said.
"Nobody else has ever done this before."
Peptides are short chains of amino acids which influence how human cells work.
They occur naturally but can also be created synthetically.
The breakthrough came after scientists in Wolverhampton demonstrated that particular peptides could penetrate sperm cells.
Then fertility experts at Aveiro University in Portugal, who had identified the crucial protein which drives sperm to swim, created a bespoke compound which turned the protein off.
The approach was tested in the lab on bovine and human sperm, with live animal tests due to start within three years.
Prof Howl said it was "too early to say" if the end result would be a pill, a nasal spray or a sub-skin implant, but said all three were possibilities.
Research has suggested that around half of sexually active men would consider taking the male contraceptive pill.
Other studies are examining the use of injections to block sperm.
John Guillebaud, emeritus professor of family planning and reproductive health at University College London, said a reversible male contraceptive would be "of enormous benefit to many couples", including when women could not take the pill for medical reasons.
"It would also help men who want to have control over their own fertility - for example, to ensure they do not get trapped into having a child by a woman who says she is on the Pill, but isn't," he said.