In search of a male contraceptive, scientists seek to stop sperm in their tracks

In search of a male contraceptive, scientists seek to stop sperm in their tracks

Illustration of reduced sperm count.
Illustration of reduced sperm count.

Condoms have been used to prevent pregnancy since the Middle Ages, with the rubber version arriving in the mid-1800s. Over the years they have become more effective and comfortable to use.

But it was the invention of birth control pills, followed by IUDs in the 1960s, that created a seismic shift in humans’ ability to control reproduction. A growing range of pills, patches and implants have become available for women. And yet, a stretchy sheath that covers the penis remains the only medically approved form of birth control for men, aside from vasectomy.

But now researchers are looking at hormonal and non-hormonal contraceptives for sperm carriers. The hope is that couples will begin to see contraception more as a shared responsibility.

“We would like to create a menu of options for men similar to what women have available to them,” says Stephanie Page, a researcher and endocrinologist at the University of Washington.

(Note: The studies referenced here are typically done on cisgender men between the ages of 18 and 50. This story therefore refers to the drugs as “male contraception” and their target demographic as “men” or “males.” , although people of other sexes can produce sperm.)

Hormonal methods are the subject of renewed research

Dr. Page’s lab is conducting a clinical trial with researchers at 15 other sites around the world, testing a topical gel that a man applies to his shoulders every day. The gel contains synthetic hormones – a combination of testosterone and progestin – which signals the brain to reduce testosterone levels in the body. And since testosterone is necessary for the maturation of sperm, the testicles then produce fewer and fewer sperm.

Dr. Page’s study recruits couples – nearly 450 of them worldwide. Having the woman also involved means “that she’s assuming the consent as well as he is, and that they’re both really participants,” says Page.

The phased trial. In the first phase, the man applies the gel every day, but the couple still uses another form of contraception during sex. During this phase, researchers periodically monitor the man’s sperm count. Then, when the number is low enough to prevent pregnancy, the couple enters the second phase: they stop using other contraceptive methods, while the man continues to use the gel daily.

In the third and final phase, the man stops using the gel and researchers start monitoring his sperm count again. The researchers hope their results will demonstrate that the effect on fertility is reversible, much like women can regain their fertility when they stop taking birth control pills.

Brian Nguyen, an obstetrician-gynecologist and professor at the University of Southern California’s Keck School of Medicine, who also researches male contraception, says he’s encouraged by what he’s hearing from some of the men taking part. trying out the freeze, especially those “who really just want to support their female partners.”

“I hear stories about how men are really tired of hearing about their partners suffering from hormonal side effects or, in some cases, complications from IUDs or implants,” he says. “And they want to do something.”

Nguyen’s lab is also working on a hormone pill that would work similarly to the gel, and Page’s lab eventually hopes to develop an injectable hormone solution.

In the 1990s, the World Health Organization sponsored trials of male hormonal contraceptives — where men were given high doses of testosterone — but these drugs never made it to market. Researchers believed they were not effective enough to sell and the side effects were serious, including heart, liver and kidney toxicity, and a potential increased risk of prostate cancer.

Stephanie Page of the University of Washington says gels and pills currently being tested don’t pose the same risks.

“We’ve worked very hard to develop methods that don’t impact these other physiological parameters,” Page says, “So we don’t see any impact on kidney function, liver function, etc.”

As for side effects, some participants report weight gain, changes in libido, acne, or mood swings.” These, she points out, are “very similar to those some women experience using female hormonal contraceptives”.

Promising non-hormonal approaches

Another area of ​​research targets specific points in the sperm’s life cycle, including its ability to swim or fertilize an egg. These drugs are a bit more specific than hormonal ones, says Logan Nickels, director of research at the Male Contraceptive Initiative, which supports researchers working on non-hormonal contraceptives.

“They target a very specific link in the chain of generation or lifespan of a sperm and… if you were to break that link, there are no other bodily functions or any sort of broad signals that you interrupt. “In other words, someone using these methods would likely experience little to no side effects,” he says.

“The male reproductive system is really cool in that there are hundreds and hundreds of links in that chain, [so] that if you eliminate one of them, you effectively end up with an infertile man,” Logan says.

Another non-hormonal method being tested in Australia is a gel injected into the vas deferens – the tube that carries sperm to the urethra in preparation for ejaculation – and blocks sperm transport. Logan says it could be a reversible alternative to a vasectomy.

Why is it taking so long?

Page estimates that it will take another seven to ten years before any of these new methods can be sold. So why have women had to bear so much of the responsibility for contraception for so long?

“Women carry the burden of life-threatening pregnancy,” Page says. “And so the initial energy was to make sure that women had control over their own reproduction.”

And, she says, developing male contraception is more complicated. Women generally release one or two eggs per month. Men produce millions of sperm every day – a single ejaculation contains around 15 to 200 million sperm per milliliter of semen. Researchers needed to determine how low the number needed to be to reliably prevent pregnancy. They have now determined that it takes less than a million sperm per milliliter of semen, Page says.

And the FDA’s criteria for approving male contraceptives are vague.

The pharmaceutical industry and the FDA use trial data to weigh the benefits and risks for the patient. But Dr Page says that in this case the risk calculation should be different.

“When we think of the risks, what are we protecting the man from? In the case of female contraception, the woman is protected from the risk of potentially dangerous pregnancy and abortion. But with men, they are really using a contraceptive to protect their partner. If we just think of the man as one unit, obviously there should be no side effects and no risk. But I think we really have to think of couples as a dyad and that’s a shared risk “, she says.

Another barrier to the marketing of male contraceptives is the rate of effectiveness. Female contraceptive implants and IUDs are 99% effective and birth control pills are 93% effective, according to Planned Parenthood. Male contraceptives may need to be just as good at preventing pregnancy in order to sell.

“Drug companies invest millions and millions and millions of dollars in a drug before they even see a dime of profit,” Nickels says. “And so when they take these calculated risks, these calculated investments, they try to ensure that they will see their money at the end,” he says.

Nickels, Page and Nguyen all expressed optimism that a male contraceptive will be commercialized in the next decade, although funding may be a limiting factor.

Logan predicts that either the injectable non-hormonal gel or the topical hormonal gel will be the first to hit the market.

For male birth control drugs to succeed in the market, says Brian Nguyen, it’s important for men to be better informed about what women are going through.

“Men are often immune to discussions about menstruation, pregnancy, labor, infertility. There is a certain sense of invulnerability in most men because they don’t have to think about the need contraception. And the only way to address that is to have more and more open conversations with men about reproduction and their responsibility in a process that is not just a women’s issue.”

Women have been waiting for this change in mentality for a long time. But even if that doesn’t happen right away for most straight men, maybe the freedom to jump the scabbard will be motivation enough.

Audio for this episode was produced by Rebecca Ramirez, edited by Gisèle Grayson, and verified by Abē Levine. Tre Watson was the sound engineer.

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