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It takes two to cause a pregnancy. So why are birth control pills only available for one partner?
Multiple forces have dragged out the process of developing new contraceptives for men and other people with testes, and it’s not clear when exactly we’ll see more alternatives.
But that hasn’t stopped researchers from pursuing these drugs for decades, and experts who have long been involved with this effort are confident that day isn’t too far off. Several contraceptives that focus on sperm have already started human trials or will soon.
Condoms are 85 percent effective in practice compared to options like birth control pills, which have an efficacy rate of 91 percent in practice or 99 percent with perfect use – while vasectomies, though technically reversible, are generally considered permanent surgical interventions and not a solution for everyone.
Beyond those options, the absence of sperm-targeting options has contributed to an enduring dynamic in sexual relationships where people who can get pregnant are disproportionately responsible for preventing that outcome. Since it takes two to cause a pregnancy, some researchers are pushing for a reconsideration of contraception as a responsibility that requires active decision-making between two sexual partners.
READ MORE: House passes bill that would protect right to contraception
In June, the Supreme Court eliminated constitutional protections for abortion, meaning a key pillar of reproductive health care is now illegal or significantly restricted, or could be soon, in just under half of states. The curtailing of abortion rights not only raises questions about the future of contraception protections, but also highlights the barriers that already exist and disproportionately affect low-income people.
A quarter of women who don’t use their preferred method of contraception said it was because they could not afford it, according to a 2020 Women’s Health Survey from the Kaiser Family Foundation. That same survey found that just under a third of people who used oral contraceptives reported missing a pill because they could not get their next pack in time.
Following the Supreme Court’s decision to overturn Roe v. Wade, experts have warned that a comparable legal underpinning could potentially jeopardize access to contraception in the future. Opposition to some specific types of contraception, including intrauterine devices (IUDs) and Plan B pills designed to prevent pregnancy following unprotected sex, has long been a talking point in some anti-abortion circles.
In July, the House passed a bill that would cement the right to use contraception at the federal level, but it was blocked by Republicans in the Senate. Brian T. Nguyen, an assistant professor of clinical obstetrics and gynecology and director of the Fellowship in Complex Family Planning at the University of Southern California, believes it’s “absolutely essential” that the House bill become law.
“There will always be groups who have strong feelings about reproduction and while in the past, we have assumed that most groups in America would not impose their personal beliefs on those of others, we can no longer guarantee that,” said Nguyen, who conducts research on both female and male contraceptives. “Which is why it is essential that we protect contraception as a right upon which others cannot encroach.”
Here’s a look at how sperm-targeting contraception works, the barriers to getting some of these options to market and why reframing the burden of pregnancy prevention could lead to a more equitable distribution of this responsibility.
Drug development for new contraceptives is all about restricting a “target,” or function within the body, in order to prevent pregnancy, explained Gunda Georg, regents professor of medicinal chemistry at the University of Minnesota College of Pharmacy. That can be a nonhormonal option, like inhibiting a certain protein or disrupting the electrical currents sperm need to be viable, or one that interferes with hormone levels. The goal of most methods is to significantly suppress the development of sperm or interfere with their mobility to ensure they never meet an egg.
Among other projects, Georg’s team is working on a nonhormonal pill that goes after a protein called the retinoic acid receptor alpha (RAR-α) and has been proven to cause temporary sterility in mice without any major side effects. That pill is expected to enter human clinical trials early next year, Georg said.
Another nonhormonal option designed to target sperm that’s made it to human studies in India is dubbed RISUG, said Arthi Thirumalai, a physician and researcher at the University of Washington School of Medicine. This injectable method generates a physical and chemical barrier within the male reproductive tract that stops sperm.
Thirumalai and her colleagues focus on hormonal contraception options, several of which have made it to human trials. The goal of those contraceptives is to introduce a drug that can safely tinker with hormonal systems to suppress sperm production, Nguyen said. Picturing a thermostat, he added, can help explain how that process works.
In a house, a thermostat is constantly measuring the temperature and keeping it at an optimal level, much like the pituitary gland keeps an eye on hormone levels like testosterone and progesterone throughout the body from its perch in the brain, Nguyen explained. If those hormone levels get too high, the pituitary gland will send orders to the testes to stop producing testosterone. Interfering with that process causes sperm count to drop to levels that are virtually impossible to cause pregnancy (as in, the count would be on par with the protection other types of hormonal birth control offer. No method can be 100-percent effective all the time).
Two notable types of hormonal contraceptives that have made it to human trials include a gel and a pill. The gel, which requires daily application to the shoulders or upper arms, contains both testosterone and a type of progesterone to suppress hormones in the brain and in turn lower testosterone production. Once participants’ sperm count drops below one million per milliliter, that level is considered effective to prevent pregnancy.
While the gel is a mix of two hormones, the pills are a sort of hybrid, single molecule that can interact with both androgen and progesterone receptors in the body much like a key engages with a lock, Nguyen said. In a Phase 1 study, two different formulations and doses of these pills were taken by participants for 28 days.
Four weeks isn’t long enough to fully suppress sperm production — spermatogenesis takes more than two months from start to finish — but the pills did successfully suppress testosterone production, said NYU Long Island medical student Tamar Jacobsohn, who is also the lead author of an abstract on this research. The second phase of the study, which lasted around three months, examined the impact on sperm production, but researchers are still analyzing that data.
Nguyen emphasized that the goal of researchers who work on hormonal contraception is to counterbalance dropping testosterone levels so that users don’t lose out on the usual functions of that hormone or endure unwanted side effects. The gel, for example, offers a source of external testosterone to balance the levels that are dropping internally in order to suppress sperm development.
But the goal of preventing side effects is not foolproof. Just as some people cannot tolerate the side effects of existing hormonal contraception, the same will likely be true for future products that target sperm.
Some side effects that have come up in clinical trials for hormonal options include changes in libido; weight; acne; hematocrit, i.e. the proportion of red blood cells in the blood; and cholesterol. One clinical trial involving an injectable form of hormonal contraception stopped enrolling new participants after existing ones reported a range of side effects. Of primary concern was one participant developing severe depression, and another attempting suicide, as reported by NPR in 2016. Twenty men dropped out of the study citing side effects, but more than 75 percent said they would be willing to use the contraception method tested within the trial when it ended, according to the Endocrine Society.
While evidence suggests that hormonal options are farthest along in clinical trials, have largely promising side effect profiles and are most likely to hit the market first, experts say nonhormonal options will be important, too.
“There’s going to need to be a menu — just like there is for female contraception — where there are different products with different characteristics because there’s not going to be one silver bullet,” said Logan Nickels, research director at Male Contraceptive Initiative, which primarily focuses on nonhormonal options. MCI is a nonprofit organization that advocates for and funds research in the field of contraception, including some of Georg’s work.
There’s a long-running joke that hormonal contraception for people with testes will be available in just “10 more years,” Jacobsohn said. Really, it’s been under research for “upwards of 50 years.”
So what’s the hold up? For one, early options required injecting testosterone, Georg noted, a more invasive method compared to taking a pill or applying a gel. It’s also been hard to effectively deliver testosterone orally through a pill, which research suggests is a form of birth control men are more excited about compared to other formulations, Jacobsohn noted.
Additionally, contraceptives designed to target sperm are meant to prevent pregnancy in someone other than the person taking them. That dynamic — one person taking a drug and opting into any potential side effects so that there aren’t physical consequences for someone else — is relatively uncommon in medicine.
People who can get pregnant take birth control because the risk-benefit ratio is more of a no-brainer: The medical risks of unwanted pregnancy and childbirth must outweigh the potential side effects of contraception. But for people with testes, the burden of pregnancy isn’t physical so much as emotional and socioeconomic.
With very different risk-benefit discussions, “the safety bar is just that much higher for a male contraceptive than for a female contraceptive method,” Thirumalai said, and there’s not a lot of regulatory guidance from institutions like the Food and Drug Administration on what those safety standards should be.
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The point of FDA-approved trials is to ensure that any drug that makes it to market has been extensively screened for its safety and efficacy. It’s up to that agency to determine what a logical path to approval looks like for any drugs that allows users to safely control their own fertility. When it comes to the social and emotional benefits, and of furthering conversations around contraception among sexual partners, that part is hard to quantify.
On a practical level, there’s also much more money to be made in other types of novel drugs compared to contraceptives, which simply aren’t the moneymakers most companies are interested in focusing on, said Robin Feldman, an expert in pharmaceutical and intellectual property law.
“If you look at the dollars being spent in this country on contraceptives in comparison to other competing types of drugs like cancer drugs, you can see how small the market is in pure dollar terms,” Feldman said.
Thirumalai also noted that much of big pharma’s hesitation to fund this research may have to do with its own uncertainty around whether these drugs will end up being used. But there’s evidence that men are interested in them. A 2002 multinational survey of more than 9,000 men found that more than half of participants said they would be willing to use a novel contraceptive option designed for men. To get a more current picture of that question, Nguyen is working on a new study that looks at the willingness of around 2,000 men in the U.S. to use contraception, as well as their attitudes around gender equity.
Nguyen sees potential benefits for men who could one day take birth control, like incentivizing them to seek medical care in a way similar to women seeking contraception options, thus expanding other important health screening opportunities. He noted that women, who must typically see a provider before getting contraceptives, are more likely to seek and receive health care than men.
He also noted the possibility for relationship gender dynamics to evolve when partners have more contraception options available, offering a chance to discuss what a gender-equitable division of reproductive responsibility would look like for them. That potential cultural change, Nguyen said, is “unquantifiable.”
Maybe you’ve seen a meme in recent months that recaps a pertinent piece of math: “If a woman has sex with 100 random men in a year, she can still only produce one full term pregnancy. If a guy has sex with 100 random women in a year, he can produce 100 full term pregnancies,” Twitter user @870South wrote back in 2019. That basic biological equation begs the question of why we don’t see preventing pregnancy as an equal responsibility, let alone why people who can become pregnant may face unequal regulation of their reproductive rights.
In a 2020 paper, Nickels and his colleagues lay out an ethical argument for “shared risk” of pregnancy, or the concept that “accounts for the interdependent nature of family planning.”
The co-authors define that risk as the sum of all risks between two people in a sexual relationship “associated with contraceptive use by either or both members,” compared to the risk of unintended pregnancy to the pair. In other words, risks and benefits are weighed between both members of a sexual partnership, as opposed to just the person taking contraception or aiming to preventing unwanted pregnancy. That goes for monogamous and non-monogamous relationships.
Nickels likens the choice to have a child to the safeguards on a nuclear weapon. Ideally, both people have to consent, like the two-man rule designed to prevent accidental warfare, where they stand together, put their keys in and turn them at the same time.
He, like other researchers in the field of contraceptive research and development, are pushing for a world in which all people have access to a long list of contraceptive options that will work well for them, and even be enjoyable to use. When people with testes will see that day, and whether it will be a handful of years or another 10, remains to be seen.
“Regardless of their gender, of their identity, of their orientation, anyone should be able to choose if and when they have children,” Nickels said. “And there should be tools out there to allow them to achieve that.”
Bella Isaacs-Thomas is a digital reporter on the PBS NewsHour's science desk.
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