Men have long had just two choices for birth control: condoms or sterilization. Now early lab tests in mice

suggest that there might be another option on the horizon.

These preliminary lab tests suggest that it might one day be possible to give men a birth control pill they can take as-needed before sex.

This pill is so new that it doesn’t have a name — it’s just called TDI-11861 — and it works by stopping

sperm from traveling through the female reproductive tract to fertilize an egg.

An On-Demand Male Birth Control Pill

In early lab experiments, a single dose of TDI-11861 immobilized mice sperm for up to two and a half

hours, according to results published in Nature Communications. Some sperm started moving again after

three hours, and nearly all sperm regained mobility after 24 hours.

No pregnancies resulted when male mice were given this drug before mating with females. By contrast, male mice that didn’t get the drug impregnated females about one-third of the time.

This suggests that men might one day be able to take a birth control pill as-needed before sex to prevent

pregnancy, say the study’s senior authors Jochen Buck, MD, PhD, and Lonny Levin, PhD, professors of

pharmacology at Weill Cornell Medicine in New York City.

“Men would only take a contraceptive when, and as often, as they need,” Drs. Buck and Levin said jointly by email.

Proper Timing Will Be Key for Any Future Male ‘Pill’

There is a big caveat, however: Men will have to use it properly.

“We anticipate that the ultimate drug we develop will be active within 30 minutes of taking it and will remain active — with the man infertile — for 12 to 18 hours,” Buck and Levin said. “The man will have to watch the clock to ensure he does not exceed the active window.”

The experimental drug belongs to a new family of medicines that are designed to block a protein known as soluble adenylyl cyclase (sAC), which plays a key role in helping sperm mature and move. So far, TDI-11861 appears to be a fast-acting sAC inhibitor that works with a single dose and wears off afterwards. This means that men wouldn’t be infertile for very long — only long enough to prevent pregnancy in the hours immediately after use.

Normally, sperms start swimming vigorously through the vagina after ejaculation so they can move up through the cervix and into the uterus, Buck and Levin noted. Once in the uterus, sperm can survive for several days, making it possible for a pregnancy to occur several days after intercourse.

“However, sperm which come from a man who took an sAC inhibitor will be immotile, which means they will remain trapped in the vagina and never penetrate the cervix,” Buck and Levin said.

How Soon Could Male Birth Control Be Available?

They plan more studies in mice before they start human trials. Buck and Levin said they hope to start human studies within two to three years.

While this concept of immobilizing sperm to prevent pregnancy is intriguing, one open question is

whether this experimental drug would remain active the entire time sperm remain in the female

reproductive tract in order to reliably provide contraception, says Stephanie Page, MD PhD, a

contraceptive researcher and professor at the University of Washington School of Medicine in Seattle,

who wasn’t involved in the new study.

“In humans, sperm can live in the female reproductive tract for a few days, so an effective method of contraception targeting this aspect of male fertility may need to last at least 48 hours and perhaps longer,” Dr. Page says.

Because this new pill would be given to healthy men, the pill will also have to be extremely safe for men to take it, says Gunda Georg, PhD, a contraceptives researcher, professor, and director of the Institute for Therapeutics Discovery and Development at the University of Minnesota in Minneapolis.

“Having an agent for on-demand contraception is an exciting idea,” says Dr. Georg, who wasn’t involved in the new study. “Men would not need to take the pill every day and only before intercourse, and occasional use of the sAC inhibitor lowers the possibility that men would experience potential side effects from the drug.”

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