On-Demand Male Birth Control Immobilizes Sperm and Completely Wears Off in a Day

Late last year, a Virginia-based startup called Contraline started the initial clinical trial of its male birth control, a hydrogel that’s injected directly into mens’ vas deferens (the tube that carries sperm from the testes to the urethra) to block sperm from passing. Trial participants will be monitored for the next three years, with doctors keeping an eye on the gel’s effectiveness and safety. Though the method seems promising, it will require men to both plan ahead and undergo a slightly invasive procedure (if getting a single shot can be considered invasive).

A new method that was successfully tested in mice is quicker, simpler, and could eventually be used in humans. It comes in the form of a pill that men would take 30 minutes to an hour before sex. Its effects are strongest for the ensuing three hours, and it fully wears off within 24 hours.

Described in a paper published this week in Nature Communications, the pill works by inhibiting the function of a protein called soluble adenylyl cyclase (sAC), which is essential for sperm motility and maturation. Dr. Melanie Balbach, a postdoc at Cornell, discovered that mice that were given a drug to inactivate sAC produced sperm that couldn’t propel themselves forward.

A small percentage of men lack the gene that encodes for sAC, and these men are infertile but otherwise healthy. Knowing there were no negative side effects of inhibiting sAC allowed the team to move forward with investigating it as a contraceptive option; since it’s non-hormonal, there’s no risk of it impacting testosterone or causing male hormone deficiencies.

The team partnered with drug discovery scientists to develop a sAC inhibitor called TDI-11861. Male mice who were given a dose of the drug didn’t impregnate any females even after 52 mating attempts. In the control group, meanwhile, about a third of the females became pregnant from male mice not given the drug.

A major advantage of this method, if it were to translate to humans, is how quickly it works and how quickly it stops working. “Our inhibitor works within 30 minutes to an hour,” Dr. Balbach said. “Every other experimental hormonal or nonhormonal male contraceptive takes weeks to bring sperm count down or render them unable to fertilize eggs.” It also takes weeks to reverse their effects, while sAC inhibitors wear off within hours. Men could take it only when needed, making day-to-day decisions about their fertility rather than committing to a multi-month or multi-year option.

But getting men to share the burden of birth control will likely take more than having options available, even if those options are as straightforward as the sAC inhibitor seems. The predominant line of thinking is that birth control is womens’ responsibility, never mind the severe side effects that come with many forms of female birth control. What might it take for men to not only get used to the idea of male birth control, but willingly partake in it?

Allan Pacey, a professor of andrology at the University of Sheffield who was not involved in the study, thinks the sAC inhibitor could be a gateway solution. “There is a pressing need for an effective, reversible, oral contraceptive for men and although many different approaches have been tested over the years, none has yet reached the market,” he said. “If the trials on mice can be replicated in humans with the same degree of efficacy, then this could well be the male contraceptive approach we have been looking for.”

Image Credit: Mohamed Hassan from Pixabay

Vanessa Bates Ramirez
Vanessa Bates Ramirez
Vanessa is senior editor of Singularity Hub. She's interested in biotechnology and genetic engineering, the nitty-gritty of the renewable energy transition, the roles technology and science play in geopolitics and international development, and countless other topics.
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