A short-term contraceptive drug that temporarily disables sperm in male mice was found to be effective, according to Weill Cornell Medical Center in New York City. Scientists are now closer to developing a fast, short-acting birth control pill.
The study, funded by the National Institutes of Health, gave male mice a single dose of a compound that temporarily inhibited soluble adenylyl cyclase (sAC), “the enzyme essential for activating a sperm cell’s ability to swim and mature so that it can travel through the female reproductive tract and fertilize an egg.” The study found that male mice treated with the compound exhibited “normal mating behavior” but resulted in zero pregnancies, whereas male mice given a placebo impregnated their mates 30% of the time. The compound made the male mice infertile for 2.5 hours. Some sperm returned to normal within 3 hours. The male mice were able to regain full fertility in 24 hours. No side effects were observed in female or male mice.
A nonhormonal, ‘on-demand’ approach
In an email to Yahoo News, the study’s coauthors, Dr. Lonny Levin, Dr. Jochen Buck and Dr. Melanie Balbach, said there were several major takeaways from their research.
“The first is that male contraception is an achievable goal,” Levin said. “Our study provides proof of concept that a man will some day be able to take a contraceptive drug to provide reproductive equality for both partners.”
Nearly half of all pregnancies are unplanned, according to the United Nations’ sexual and reproductive health agency, with the burden of preventing pregnancy disproportionately falling on women. The study notes that for years, condoms and vasectomies have been men’s only birth control options, but the new method of contraception “has the potential to provide equity between the sexes and, like the advent of oral birth control for women, revolutionize family planning.”
Researchers used a nonhormonal approach to study. This has one advantage: It does not cause unwanted side effects like conventional hormonal birth control pills. In a news release, Levin noted that the field of male oral contraceptive development assumes that the side effects of hormonal contraceptives might deter men from using them, and that men are likely to have a low tolerance for side effects, because they “don’t bear the risks associated with carrying a pregnancy.” Hormonal regimens have been about 94% effective at preventing pregnancy in clinical trials, the study notes, but have been abandoned, given the side effects, such as acne and mood swings.
The authors also told Yahoo News that their approach proves that “on demand contraception” is feasible, as opposed to taking oral contraceptives on a regular basis.
“We provide proof of concept that [it] is possible for a person (in our study, it is specific for men, but there is a future possibility that the same can be achieved for women) to take a pill for contraception only when and as often as needed,” Levin said.
“In our approach, the man will take a pill shortly before sexual activity, and they will be infertile for the subsequent 12-18 hours. They will become fertile again the next day. This approach means that men will only be taking a treatment when needed.”
What’s next?
The study’s authors said they are now testing the sAC-inhibiting compound in rabbits, whose reproductive system is similar to humans’, while also further improving their preclinical drug candidates.
“With one of these compounds, we will start clinical trials in humans in two to three years,” Balbach said. “Usually, the first phase of a clinical trial exclusively focuses on safety. We have the advantage that we can not only test for safety, but we can also test easily right away if the sAC inhibitor blocks sperm motility in humans, similarly as in mice.”
Balbach said that assuming all goes well, “We hope we have a pill on the shelves in six to eight years.”
