Birth control pill for men !

US researchers have stumbled upon a compound that may finally lead to a birth control pill for men.

In lab experiments, male mice given the pill were rendered completely infertile during treatment as they produced fewer and less mobile sperm. The drug, originally tested as part of a broader cancer research project, does not affect the hormone system or sex drive, according to the researchers.

"There is no effect on the mouse's mojo. The animals exhibit the normal sexual behaviours and frequency of copulation," says Dr James Bradner of the Dana-Farber Cancer Institute in Boston, whose study appears in the journal Cell.

What's more, the effect is completely reversible. Once doctors stopped giving the drug to mice, they were able to sire healthy litters, with no apparent side effects, says Bradner.

Scientists say the research is exciting because it applies a unique approach to the problem of male contraception, which is now largely comprised of less reliable methods like condom use, or more permanent procedures like vasectomies.

Bradner's lab focuses on developing new drugs to undermine the molecular memory of cancer cells that tell them to divide. Those memory markers are distributed throughout the genome, the DNA that makes up a person's genetic code, and Bradner likens them to post-it notes that give cells instructions.

The team was experimenting with a compound developed in Bradner's lab called JQ1, which was originally synthesised at Dana-Farber to block BRD4, a cancer-causing gene.

They discovered that it appears to target a protein specific to the testes called BRDT that instructs sperm to mature. Bradner says the compound does not appear to do damage to sperm-making cells, but they forget how to create mature sperm while under the influence of the drug.

Bradner reached out to reproductive health expert Martin Matzuk of Baylor College of Medicine, another author of the report, and his team tested the compound in mice.

What they found is that the animals began producing fewer sperm, and the ones they did produce were poor swimmers.

"When the drug is removed, these instructions return," says Bradner.

The finding was surprising because few drugs are able to cross a protective firewall known as the blood-testes barrier that protects the testicles from substances floating around in the blood stream.

William Bremner from the University of Washington in Seattle, who was not involved in the research, says finding is "a breakthrough new approach," noting that there has not been a new reversible contraceptive for men since the development of the condom centuries ago.

"It's exciting basic science that provides a new approach to think about how a contraceptive for men might be designed," says Bremner. "At the same time, it's a long ways from being in clinical trials in men, let alone being on pharmacy shelves."

Other teams have developed hormonal pills that are effective, but they disrupt hormone balance in men, and drug companies so far have not picked up on this approach, says Bremner.

Professor Moira O'Bryan, head of the Male Infertility and Germ Cell Biology Laboratory at Monash University in Australia, says the study was "an exciting report that could have major scientific and social impacts."

O'Bryan says the strong similarity between sperm production in mice and humans suggest that a variation of the drug may ultimately result in a human contraception for men.

Professor Robert McLachlan, Director of Clinical Research at Prince Henry's Institute of Medical Research in Melbourne adds that it will be sometime before it is likely to be used in humans.

"The development of a potential contraceptive is a very long and arduous process leading up to the first human studies," says McLachlan.

"It will be fascinating to see how the drug evolves, but we know that such pipelines may require 15 years of evaluation and there are many potential pitfalls along the journey."

Bradner says his team is working to refine the drug so that it only acts on cells in the testes, and not on cancer cells.

And while there are many more tests ahead before it can be a drug, the researchers believe the new approach can be "completely translated to men, providing a novel and efficacious strategy for a male contraceptive."