Experimental ‘On Demand’ Male Birth Control Temporarily Immobilizes Sperm to Prevent Pregnancy

A new method of male birth control temporarily renders sperm immobile and unable to cross the cervix into the vagina. Shutterstock/koya979

An experimental male birth control drug has been shown to temporarily paralyze sperm in mice and effectively prevent pregnancy for over two hours with full fertility returning after 24 hours. The effectiveness rate of the drug in mice clocked in at 100 percent.

According to a Feb. 14 study published in the journal Nature, scientists experimented with soluble adenylyl cyclase (sAC), a protein that is essential for sperm motility and maturation. Earlier studies had shown that men who could not produce sAC were infertile while being otherwise healthy.

In this study, scientists from Weill Cornell Medicine looked at the potential of using sAC inhibitors as a male contraceptive. Once sperm become immobile, they can not travel through the vaginal tract and fertilize eggs.

The research found that a single dose of an sAC inhibitor called TDI-11861 was capable of immobilizing the sperm of male mice for a period of up to two and a half hours. Even after mating, the effect of the inhibitor persisted in the reproductive tract.

“Sperm from a man who has taken a long residence time sAC inhibitor contraceptive should not be able to cross the cervix and will remain trapped in the vagina. As the vagina re-acidifies soon after copulation, sAC-inhibited sperm would not persist long after sex,” the study states.

The temporary immobility of sperm began to wane after three hours and vanished after 24 hours, after which almost all sperm were once again able to move normally.

In tests, male mice treated with TDI-11861 inhibitors did not impregnate even a single female after mating, despite 52 different mating attempts.

“A sAC inhibitor with suitable pharmacokinetics, oral bioavailability, long residence time, and safety profile can be formulated into an oral male birth control pill, which a man would take shortly before sex, providing protection from unwanted pregnancy for the subsequent hours,” according to the study.

Quick Acting Contraceptive Without Side Effects

Melanie Balbach, a postdoctoral associate in pharmacology at Weill Cornell Medical College and one of the scientists in the study, points out a major difference between male birth control using sAC inhibitors and other solutions in development.

“Our inhibitor works within 30 minutes to an hour,” she said, according to a Feb. 14 press release by Weill Cornell Medicine. “Every other experimental hormonal or nonhormonal male contraceptive takes weeks to bring sperm count down or render them unable to fertilize eggs.”

Men can take sAC inhibitor pills when they need, as often they need, enabling them to make decisions regarding their fertility on a daily basis, she stated.

To ensure the safety of the sAC inhibitor, scientists continuously infused the compound in mice for six weeks. They observed no side effects.

Other Forms of Male Birth Control

At present, hormonal birth control solutions for men usually require long-term injections and can result in side effects.

For instance, testosterone injections block the release of pituitary hormones that signals the testes to generate sperm. Sperm counts are reduced after weekly or monthly injections. Side effects include abnormal blood lipid levels, weight gain, and acne.

Combining hormonal injections, like those involving testosterone undecanoate and norethisterone enanthate also requires injections on a regular basis and come with side effects like muscle pain, acne, mood swings, and so on.

Non-hormonal solutions include vasectomy which involves cutting or tying up the vas deferens, a tube through which the sperm is transported from the testicle to the urethra.

This is seen as a permanent form of birth control for men. Even though some vasectomies are claimed to be reversible, the effectiveness of such procedures is not guaranteed.