An emerging male birth control option may be even more attractive to potential users than expected. Preliminary research published on Sunday suggests that NES/T – a gel applied once daily to the shoulders – can effectively suppress male fertility within a few weeks.
NES/T is an acronym for the two main ingredients it carries, nonsterone and testosterone. Nestorone, also known as segesterone acetate, is a synthetic version of progesterone, a hormone that plays a major role in regulating pregnancy and other reproductive functions. Nestoron and similar drugs are already used as hormonal birth control in women. When given to men, the drug lowers the levels of hormones in the testicles responsible for male fertility, including testosterone, which then leads to a low sperm count. But it also reduces testosterone circulating in the blood, which can counterproductively reduce men’s sex drive, among other adverse effects. By re-introducing synthetic testosterone through the gel, the goal is to maintain stable hormone levels in men’s blood, providing temporary sterility and minimizing side effects.
The gel is being developed with the help of several organizations, including the US government’s National Institute of Child Health and Human Development (NICHD), part of the larger NIH. It is now being tested in a larger phase IIB study involving about 400 couples. This trial is still ongoing, but researchers have already begun to examine some of the available data, which has provided encouraging results. In the summer of 2022, for example, Diana Blythe, head of the NICHD’s Contraceptive Development Program, reported that the efficacy rate of the NES/T gel so far appear to be equal to or even better than hormonal contraceptive options for women.
In this new research, presented at ENDO 2024 weekend, Blithe and her team looked at the timing of the NES/T gel’s effectiveness. Based on other studies of hormonal birth control in men, Blythe and her team expected that most men’s sperm count would begin to be sufficiently suppressed between the 12th and 15th week. But they were pleasantly surprised at how much less time it took many of their subjects.
Of the 222 participants whose sperm were checked within 15 weeks of starting treatment, 86% overall achieved sperm count suppression. Within five weeks, about 20% were suppressed; by week eight, 52% were suppressed, and by week nine, 62% were suppressed. And among those who were suppressed, the average length of time was only eight weeks. Because Blithe’s team did not expect these results at the outset, many participants did not have their sperm tested between weeks four and eight. So it is possible that the average suppression time is even shorter than estimated.
“We are really pleased with this result. And we think that will make the gel more attractive to people who maybe didn’t want to wait three months for it to be effective,” Blythe told Gizmodo by phone.
The findings are still preliminary, and it will take more time for the complete phase II data to be collected and analyzed. But Blythe and her team are encouraged by everything they’ve seen so far. In the team’s early evaluations, the gel appears to be both effective and safe, with minimal side effects for men who take it.
“I think there’s a lot of bad publicity about hormonal methods for men that makes the expectations quite scary for people, but that maybe works in our favour. “People are signing up and realizing, ‘Oh, nothing bad happened, this is great,'” Blythe said. “We’re quite pleased with the limited side effects we’ve seen.”
Blithe and her colleagues are set to meet with the FDA next year about the steps needed to begin a larger phase III study and are still looking for a commercial partner to help bring the NES/T gel to market. So it will be at least a few more years before men can potentially get their hands on the product. But for now, the future of male birth control still looks bright.
