BETHESDA, Md. — A male contraceptive pill could create an “on-demand” way for men to prevent pregnancy. Researchers from the National Institutes of Health say the compounds in this drug block a fertility protein for 24 hours. Moreover, men could take the contraceptive right before sex and still get full protection.
Scientists say that, in some ways, it is more effective than women’s oral birth control medications, which users have to take daily. In experiments, the non-hormonal compound stopped mouse sperm cells in their tracks, preventing them from maturing. The animals’ sexual functioning was normal. Male lab rodents mated with females, but there were no pregnancies.
“Our inhibitor works within 30 minutes to an hour,” says lead author Dr. Melanie Balbach, in a statement. “Every other experimental hormonal or non-hormonal male contraceptive takes weeks to bring sperm count down or render them unable to fertilize eggs.”
How does the male birth control pill work?
The drug temporarily disables an enzyme called sAC (soluble adenylyl cyclase), which triggers the sperm cells to swim. Researchers note that sperm recovered from female mice remained incapacitated and there were no side-effects in males taking the drug. The compound wore off three hours later, with male mice recovering their fertility right after.
A single dose rendered sperm immobile for up to two-and-a-half hours, with the effects persisting in the female reproductive tract after sex. There were 52 attempts at impregnation and all failed. In contrast, one in three mice treated with a placebo that acted as a control group got their partners pregnant.
After three hours, some sperm began regaining motility, with virtually all recovering a day later. The team at Weill Cornell Medicine in New York is hailing the breakthrough as a potential “gamechanger” for preventing unwanted pregnancies.
Scientists have been trying to develop an effective male oral contraceptive for decades. Targeting testosterone has previously led to obesity, depression, and high cholesterol. Women’s choices range from pills to patches to intrauterine devices. As a result, they bear most of the burden of preventing pregnancy.
Men have just two options, condoms or a vasectomy. The former is a single-use option and prone to failure. The latter is surgical sterilization which is expensive to reverse and not always successful. It takes weeks to reverse the effects of other hormonal and non-hormonal male contraceptives in development, according to Dr. Balbach.
The new treatment wears off within hours. Men would take it only when, and as often, as needed. It could allow men to make day-to-day decisions about their fertility, the researchers explain.
“The team is already working on making sAC inhibitors better suited for use in humans,” notes co-author Professor Lonny Levin.
Creating a pill for men has been a difficult process
The team has already launched Sacyl Pharmaceuticals. The next step is repeating the study in a different pre-clinical model to lay the groundwork for human clinical trials. They would test the effect on sperm motility in healthy human males. If successful, Prof. Levin adds that he hopes to walk into a pharmacy one day and hear a man request “the male pill.”
The findings, published in the journal Nature Communications, are among the most promising to date — offering real hope of bringing this goal to fruition. It would help reduce unintended pregnancies and abortions, as well as improving maternal health and decreasing infant mortality.
The female pill has enabled millions of women take control of their fertility and reproductive health since it became available in 1961. Its convenience and non-invasiveness has provided little incentive for pharmaceutical giants to develop a male equivalent.
A recent study that injected men with testosterone and progestogen – similar to hormones found in the female pill – had to be stopped early. Pregnancy rates for female partners of men receiving the injections fell below that typically seen for women on the pill. Adverse side-effects included acne, mood disorders, and raised libido. The side-effects proved to be too severe, despite the desired drop in sperm production.
South West News Service writer Mark Waghorn contributed to this report.