Condoms are so passé. After thousands of years of using various sheaths to stop semen from turning into one-half of a baby, lately, humans have gotten more creative in the contraception game. Recent non-starters have included snortable birth control, a penis-corker called JifTip (really), a contraceptive shot, and a surgery-free vasectomy. Now a promising birth control gel, rubbed into a man’s shoulders and back, is being developed by scientists with the US National Institutes of Health.

The government agency announced Wednesday that it would begin clinical trials of a gel called NES/T, which contains a combination of testosterone and the synthetic sex hormone progestin (in a formulation known by the brand name Nestorone).

Together, these hormones can help reduce sperm count, preventing pregnancy, but still maintain a man’s horniness: Progestin’s role is to reduce the amount of testosterone in the testes, which in turn shuts down sperm production. But to make up for any loss in sex drive due to that decrease in testosterone, NES/T includes some extra testosterone for the body to use outside of the testes.

The new trial is a follow-up to a smaller study on the gel that began in 2012.

A new topical gel could spell the end of male condoms, if this trial succeeds. Flickr / Wesley Fryer

It all sounds far less cumbersome than a condom, but of course there are some risks to the approximately 420 healthy, heterosexual, and international couples enrolled in the study. The ClinicalTrials.gov page for the study lists various criteria both male and female participants must acknowledge, most prominently: “Willingness to accept a low but unknown risk of conceiving a pregnancy for the duration of the trial.” This is a study meant to lead to the development of a birth control gel for men — so there’s no guarantee the current formulation works just yet.

Men involved in the study will have to apply the gel daily, after showering in the mornings, for four to 12 weeks, during which the US Population and National Institute of Child Health and Human Development researchers will check for side effects and sperm count. The sperm count is expected to decline over time, but nobody is quite sure how many days of gel-rubbing it will take.

Once the men’s sperm levels are low enough that they likely won’t cause pregnancy, the couples will rely solely on daily gel-rubbing for contraception, and the researchers will continue to keep tabs on their pregnancy status for the next 52 weeks.

“Many women cannot use hormonal contraception and male contraceptive methods are limited to vasectomy and condoms,” said study investigator Diana Blithe, Ph.D., chief of NICHD’s Contraceptive Development Program. “A safe, highly effective and reversible method of male contraception would fill an important public health need.”

As with most types of birth control we’re familiar with, the most important factor is whether individuals will actually remember to use it. Fortunately, with this gel, “there is a bit of forgiveness,” Régine Sitruk-Ware, Ph.D., a Population Council scientist, told MIT Tech Review in 2017. If used properly, NES/T can keep sperm levels low for about 72 hours before it’s time to slather more on.