Breakthrough contraceptive pill for men claims to have 100 per cent success rate

Researchers are hailing a new male contraceptive pill as a game changer after a promising US Government-funded study.

The drug is taken 30 minutes before sex and appears to be 100 percent effective at stopping pregnancies for at least two hours.

It works by halting men’s sperm swimming towards eggs or maturing to the stage where it is able to fertilise an egg to create a baby.

While only proven to prevent pregnancy in mice so far, there is good evidence suggesting the contraceptive will work in humans.

Currently there is no male version of the Pill, with condoms and vasectomies the only option for male contraception.

The study was funded by the National Institutes of Health, America’s medical research agency.

The drug targets the enzyme adenylyl cyclase, which gives sperm the ability to swim through the female reproductive tract and fertilise an egg.

The enzyme is naturally missing in a small number of men — and they are infertile.

It suggests that healthy men given a drug to block the enzyme would be made temporarily infertile too.

Researchers hope the drug could be used by men, last for 16 hours, then wear off the next day.

Using groups of mice, the researchers performed a series of experiments and found that the drug eliminated the mice’s fertility in just 30 minutes.

Promisingly, it did not interfere with their mating behaviour.

The male mice still mated with the females but no pregnancies occurred. Sperm collected from the female mice remained debilitated.

According to the study, contraceptive effectiveness was found to be at 100 percent in the first two hours and 91 percent in the first three hours.

By 24 hours, it had returned to normal levels.

Researchers found no negative health impacts when the drug was continuously given to the mice for six weeks.

Although the scientists administered the drug via injection in most experiments, they found that mouse sperm mobility was also reduced by similar levels when taken orally.

Melanie Balbach, a postdoctoral associate, said: “Our inhibitor works within 30 minutes to an hour.

“Every other experimental hormonal or non-hormonal male contraceptive takes weeks to bring sperm count down or render them unable to fertilize eggs.”

Dr Balbach explained that since sAC inhibitors wear off within hours, and men would take it only when and as often as needed, it would allow men to make day-to-day decisions about their fertility.

Further studies are needed but if the drug development and clinical trials are successful, researchers hope to walk into a pharmacy one day and hear a man request “the male pill”.

Allan Pacey, professor of andrology at the University of Sheffield, said: “The approach described here, to knock out a key enzyme in sperm that is critical for sperm movement, is a really novel idea.

“The fact that it is able to act — and be reversed — so quickly is really quite exciting.

“If the trials on mice can be replicated in humans with the same degree of efficacy, then this could well be the male contraceptive approach we have been looking for.”

The findings were published in Nature Communications.