Contraceptive drug for men in mice is 100% effective

A male contraceptive that immobilizes sperm for 2 hours prevented pregnancy in mice and resulted in no adverse side effects.

A drug that temporarily paralyzes sperm could be the first birth control pill for men. In mice, the contraceptive was 100% effective in preventing pregnancy within about 2 hours, with full fertility restored after 24 hours.

“In the field of male contraception, this is a real revolution,” says Jochen Buck from Cornell University in New York. According to him, most other promising male contraceptives in clinical development are effective only after 8-12 weeks.

Previous research has shown that sperm cells require a protein called soluble adenylate cyclase (sAC) to move, and that men who cannot produce sAC due to rare genetic mutations are infertile. So, Buck and his colleagues evaluated whether a drug that inhibits sAC could be used as a male contraceptive. If sperm are immobile, they cannot travel through the vaginal tract to fertilize an egg.

The team evaluated the movement of sperm collected from 17 male mice, eight of which received the drug. In samples collected 2 hours after the mice received the drug, on average only about 6% of the spermatozoa were motile, compared with about 30% in the samples of control mice. The effect disappeared after about 24 hours, “which means we not only have an on-demand contraceptive, but also a rapidly reversible one,” says Melanie Balbach of Cornell University.

In another experiment, the researchers paired 52 male mice with females 30 minutes after they were given birth control. After 2 hours, each couple mated, but there were no pregnancies, which indicates a 100% effectiveness of the contraceptive. The drug also did not cause noticeable side effects, even when mice received three times the standard dose of a comparable compound continuously for 42 days.

“What I like about the contraceptives proposed in this study is that they are available upon request,” says Ulrike Schimpf from the KTH Royal Institute of Technology in Sweden. “It will act quickly, temporarily and effectively from the first dose.”

Buck and Balbach plan to improve the drug so it lasts longer before testing it in humans. If all goes well, they hope to start clinical trials by 2025.

“We need more [birth control] options, and men need an option so that the burden of contraception is no longer on women,” says Balbach. “We are very optimistic that once men take the inhibitor, it will have the same effect.”

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