(CNN) — After decades of failed attempts, researchers say that progress is finally being made in the development of a long-acting, reversible contraceptive method for men.
The experimental product is a hormonal gel that men rub on their shoulders once a day. Over time, it blocks sperm production in the testicles.
The gel has been developed by the National Institutes of Health (NIH) and the non-profit organization Population Council, and follows a very similar approach to that of birth control pills for women. It uses two hormones: segesterone acetate, a progestin, and testosterone, the male sex hormone. Segesterone acetate suppresses the production of testosterone in the testicles and, with it, the development of sperm.
But testosterone has many functions in the body: it is responsible for muscle maintenance and libido, for example, and men need some in their circulation to function normally. The gel replaces enough to keep them healthy, but not so much that they produce enough sperm to get someone pregnant.
Researchers have been formulating and perfecting the dosage and concentration of the gel since 2005. In this latest test, in which more than 300 couples participated, they believe they got it right.
Normal sperm count ranges from 15 to 200 million per milliliter of semen, and studies have shown that a count less than 1 million per milliliter is low enough to prevent pregnancy.
In a clinical trial, 86% of men reached these low counts within 15 weeks of using the gel. For some it worked even faster, suppressing sperm production within four to eight weeks.
“We were excited by the results. The combination appears to provide better and faster suppression than we expected,” said Diana Blithe, area chief of the NIH’s National Institute of Child Health and Human Development, who provided an update on the results of the study. essay this week at the annual meeting of the Endocrine Society in Boston.
Blithe did not say whether there were any unintended pregnancies during the trial. The researchers hope to publish the final data in a medical journal, and Blithe said he did not want to disclose the results.
“I would say our expectation was that it would be similar to hormonal birth control pills. And I can say that it is much, much better than that,” she said.
With typical use, contraceptive pills, rings, and patches for women have failure rates of around 7%, meaning that 7 out of every 100 women who use the method for a year will become pregnant. Condoms have a 13% failure rate.
The gel also appears to have other advantages over female contraceptives. For example, if a woman skips a day or two on the pill, she may ovulate, which increases the chance that she will have an unwanted pregnancy.
With the gel, if a man’s sperm production is completely suppressed and he misses a day or two of use, his hormones would begin to recover, but it takes 8 to 10 weeks for a man’s sperm count to recover to normal levels. that could cause pregnancy.
Blithe notes that in clinical trials, researchers are also not looking at the kind of mood swings and depression that women may experience on birth control pills.
“I would say that there is a small percentage that has mood swings that they don’t like, but it is a relatively small number. And the truth is that we have been surprised that they are so few,” he said.
The World Health Organization tested injections that used a similar combination of hormones. The approach seemed effective, but the study was stopped early, in 2011, because the injections caused too many side effects, including severe depression.
Blithe said that was because the hormones were cleared at different rates when injected. With the gel, a concentration of hormones appears to build up in the skin and create a reservoir that is released more slowly.
“That fluctuation doesn’t really occur, so we’re not creating ups and downs,” he said.
Matthew Treviño, 35, a resident of Sacramento, California, participated in the study. He rubs a little gel on each shoulder first thing in the morning and says it has become as routine as showering and brushing his teeth.
Other than a slight weight gain, he has had no complaints. If anything, her sex drive increased.
“I’ve only experienced an increase in libido,” he told the Unfold podcast, produced by the University of California at Davis, which was also one of the centers of the study. “Maybe I’m just lucky, but I hope this is the case for the majority of participants. If it is, it’s certainly going to change contraception as a whole.”
To participate in the study, couples had to be in a stable relationship and commit to participating in the research for two years.
Men are warned that the gel may have side effects, such as dry or oily skin, increased or decreased libido, hair growth or loss, and mood changes.
For Treviño’s partner, Emily Fletcher, 28, participating in the investigation meant giving up her own contraceptive method – an IUD – and taking a huge leap of faith just as the US Supreme Court overturned the case. Roe vs. Wade.
“I was worried,” she told Unfold. “The idea kept running through my mind that maybe this would be a problem if the medication didn’t work and I got pregnant.”
Fletcher and Treviño, both researchers at the University of California, Davis, ultimately felt it was important to participate in the study.
Treviño said in the podcast that he has been interested in a male contraceptive for a long time. For him, it’s not fair that his partner has to bear the burden of birth control.
Women release an egg only once a month, on average, while men produce about 1,000 sperm every second.
“Maybe the load is on the wrong side,” Treviño said. “It seems unfair to me that it falls only on women.”
After men stop using the gel, their sperm count returns to normal levels in two to three months. After the recovery phase of the trial, many of the participants became parents, demonstrating that the method is completely reversible, Blithe explained.
It’s a big step forward. Currently, the only contraceptive options for men are condoms, which have a high failure rate, and vasectomy, a surgical procedure that is difficult to reverse.
The researchers began discussions with the U.S. Food and Drug Administration (FDA) about testing the gel in a definitive trial. According to Blithe, no male contraceptive method has come this far.
Typically, drugs that reach this phase must be compared head-to-head with a placebo. But testing a real placebo in research aimed at preventing pregnancy would be unethical, according to Dr. Christina Wang, co-principal investigator of the trial and a specialist in Male Reproductive Biology at the Lundquist Institute at the University of California Harbor Medical Center in Los Angeles. .
If researchers get the go-ahead from the FDA, they hope to begin the final phase of testing in 2025. It will take a couple more years, and Wang says they will likely expand the study to more locations and recruit more couples.
Large trials also typically require considerable investment. Blithe hopes that pharmaceutical companies will be interested in the study.
Dr. Brian Nguyen, a gynecologist and obstetrician at the University of Southern California who has helped participants with social and behavioral needs during the trial, says he hopes the gel will come to market and usher in a new era. of gender equality in birth control.
“We often think that men are not aware or do not want to participate. But if we think about men who are in very close relationships, how can a woman hide that she has pain, abnormal bleeding or mood changes?” she said. “It’s a partner-targeted medication, which is very unique.”
