Study in mice suggests drug could temporarily stop sperm moving by blocking critical protein.
When it comes to contraception, men may finally have a greater choice than a condom or vasectomy, with a study in mice released this week suggesting it may be possible to develop a pill that could be taken shortly before sex.
With what some have described as a “global epidemic” of unplanned pregnancies, and surveys suggesting many men hold positive views about a potential “male pill”, it seems to be fertile ground.
But with the field littered with false starts, are we really on the brink of a new sexual revolution?
As Allan Pacey, professor of andrology at the University of Sheffield, notes, there are several challenges to developing such contraception.
“The biology is very hard,” he said. “We’re having to deal with destroying, stopping the production of, or disabling, millions upon millions of [sperm] cells, as opposed to a single egg [for women],” he said.
What’s more, the tolerance for side effects is very low for male contraceptives.
“For female contraceptives, it is different since the risk of pregnancy is weighed against the risk of contraceptive side-effects,” said Dr. Melanie Balbach from Weill Cornell Medicine in New York, adding that another barrier to the development of male contraceptives has been the societal view that the burden of contraception falls to the female because they carry the pregnancy.
One problem is that male contraceptives that use hormones to stop sperm production can lower testosterone levels, and hence affect libido.
“Making [a male] contraceptive is quite easy if you’re not bothered about having a libido, but then there’s no point,” said Pacey.
To get around the problem, researchers have added testosterone, or a testosterone-like compound to the contraceptives – an approach that has been trialed in jabs, gels and pills. Although the former hit a glitch with unpleasant side effects, trials of other methods are going well.
“We completed a second trial and are still working on optimizing the dosing of the pill,” said Stephanie Page, a professor of medicine at the University of Washington in Seattle, although she added limited resources for this effort meant the team was also working on the gel.
An alternative approach is rather more mechanical: blocking the tubes that carry sperm from the testicles, with researchers in Australia exploring the use of a hydrogel for the job that would last for two years.
In effect, such an approach would offer a reversible, scalpel-free vasectomy. But Pacey thinks the answer lies elsewhere.
“I’ve always thought that we would crack this if somebody could find a molecule or a receptor or something on sperm that could be disabled in some way,” he said.
The latest study, published in the journal Nature Communications, takes just such an approach, essentially stopping sperm from being able to move by blocking a protein called soluble adenylyl cyclase, or sAC.
Crucially, the effect is temporary.
“Here, we provide proof-of-concept for an innovative strategy for on-demand contraception, where a man would take a birth control pill shortly before sex, only as needed,” the authors of the study wrote.
While Pacey said human trials are now needed, the approach holds promise.
“As a kind of one-off prophylactic, at least on the mouse experiments, it seems to do the job,” he said.
Pacey also said the approach could pave the way for a unisex contraceptive. “I don’t see why if a woman took it, it wouldn’t have the same effect on sperm,” he said.
Balbach, a co-author of the work, confirmed it is an area the team is investigating.
While Page welcomed the new research, she said there was a long way to go before men have access to the drug as a pill.
“It is going to be a real challenge to get high enough levels of a drug into the testicle with oral dosing and that is a hurdle for much of the field,” she said, adding that as sperm can last up to five days in the female reproductive tract, an effect that only lasts hours may not work.
And developing a male contraceptive is not just about science. As Pacey notes, pharmaceutical companies also have to be onboard.
“Once you have the female pill, then what’s the incentive to develop a male pill?” he said. “Why would they invest lots and lots of money going through the regulatory stuff for something that’s going to halve their market potential?”
The landscape, however, could be shifting.
“Pharma companies indeed did not show much interest in developing a male contraceptive in the past years so funding was low. That is changing though,” said Balbach.
“Our contraceptive approach will hopefully be one of many one days,” she said. “So men get to pick what they like best.”
