A Possible Substitute for Mifepristone Is Already on Pharmacy Shelves

Over the past several years, a medication called mifepristone has been at the center of intense moral and legal fights in the United States. The pill is the only drug approved by the FDA specifically for ending pregnancies; combined with misoprostol, it makes up the country’s most common regimen for medication abortions, which accounted for more than 60 percent of terminations in the U.S. in 2023, according to the Guttmacher Institute, a research group that supports abortion rights. And yet, mifepristone is difficult or impossible to acquire legally in about half of states. Since Roe v. Wade was overturned in 2022, multiple federal lawsuits have threatened access to the pill at the national level.

Now a preliminary study suggests that using another drug in place of mifepristone may be just as effective for terminating an early pregnancy. The drug, called ulipristal acetate and sold as a 30-milligram pill under the brand name Ella, was approved by the FDA in 2010 as prescription-only emergency contraception. In a paper published today in the journal NEJM Evidence, researchers from the reproductive-rights nonprofit Gynuity Health Projects, along with partners in Mexico, reported the results of a trial in Mexico City that included more than 100 women with pregnancies up to nine weeks’ gestation. They found that medication abortion using 60 milligrams of ulipristal acetate (the equivalent of two doses of Ella) followed by misoprostol ended 97 percent of patients’ pregnancies without any additional follow-up care. (The FDA-approved regimen of mifepristone followed by misoprostol is about 95 percent effective, but because the new study did not directly compare the ulipristal acetate–misoprostol regimen to any other, researchers can’t yet say whether it’s superior or inferior to the standard regimen of mifepristone and misoprostol or misoprostol alone.)

The new study is small and did not include a control group. But the findings raise the provocative possibility that a drug already marketed as a contraceptive could also serve, at a higher dose, as a medication for abortion—a potential substitute for mifepristone, subject to fewer restrictions, wherever the latter is banned or difficult to get. The American abortion landscape, already fragmented, just got even more complicated.

Ulipristal acetate is a chemical relative of mifepristone and the most effective emergency-contraceptive pill available in the United States. When taken within five days of unprotected sex, it delays ovulation, which in turn prevents fertilization of an egg. Studies show that Ella works better than morning-after pills containing levonorgestrel, such as Plan B One-Step, and is more effective for a longer period of time after sex. Ella may also be more effective than other morning-after pills in people with a BMI above 26, which includes most American women over the age of 20. Although Ella’s 30-milligram dose is enough to prevent pregnancy, previous studies have suggested that the amount is highly unlikely to help end pregnancy as mifepristone does, by blocking a fertilized egg from implanting in the womb or disrupting the uterine lining.

Some experts have long suspected that a higher dose of ulipristal acetate could yield a different result. But the field has been generally reluctant to pursue research on the drug as a possible abortifacient out of concern for its role as an emergency contraceptive. Studies have repeatedly shown that a lower dose of mifepristone can act as an effective emergency contraceptive when taken soon after unprotected sex, with few side effects. It’s sold that way in a handful of countries where abortion is legal and widely available—but in the U.S., it was never approved for emergency contraception, and reproductive-rights advocates have not pushed for it. “Our idea, when we developed ulipristal acetate, was precisely to get away from abortion,” says André Ulmann, the founder and former chair of HRA Pharma, the drug’s original manufacturer. He and his colleagues worried, he told me, that any association with abortion would endanger their ability to market the drug for emergency contraception.

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The new study may very well validate Ulmann’s old fears. If further research confirms its findings, Americans seeking abortions may soon have a safe and effective workaround in places where mifepristone is restricted—and American abortion opponents will have a big new target. In an NEJM Evidence editorial accompanying the Gynuity study, Daniel Grossman, a professor of obstetrics, gynecology, and reproductive sciences at UC San Francisco, argued as much, writing, “There is a risk that the findings of this study could be misapplied and used by politicians to try to restrict ulipristal for emergency contraception.” Beverly Winikoff, the president and founder of Gynuity Health Projects and a co-author of the study, told me that she knew the stakes when she and her colleagues began their research. But part of Gynuity’s mission is to safeguard abortion care. In Winikoff’s view, another potential option for medication abortion in the U.S. was too important to ignore.

In 2022, a coalition of groups that oppose abortion sued the FDA in an effort to pull mifepristone off the market. In June, the Supreme Court unanimously struck down the challenge, ruling that the anti-abortion groups lacked standing. But in October, three states filed an updated version of the same suit in federal court; last week, a federal judge ruled that the case can proceed. Currently, 14 states have a near-total ban on medication abortion, and more than a dozen others limit how the drugs can be distributed, with requirements such as an in-person visit, an ultrasound examination, and a 24-hour waiting period. More restrictions may be on the way: Project 2025, the conservative-policy plan developed by the Heritage Foundation for an incoming GOP administration, calls for the FDA to entirely withdraw the drug’s approval. President Donald Trump, however, has been inconsistent, saying that he doesn’t plan to block access to the abortion pills while simultaneously refusing to rule out the possibility.

In light of the new study, it’s hard to imagine that anti-abortion groups won’t seek similar restrictions on Ella, threatening its availability as an emergency contraceptive. Anti-abortion activists and Republican lawmakers have repeatedly sought to blur the line between abortion and contraception by reasoning that pregnancy begins not, as federal law states, after a fertilized egg has implanted in the uterus, but at the moment when egg and sperm meet. Students for Life of America claims, for example, that all forms of hormonal birth control are abortifacients. “Abortion advocates have long denied Ella’s potential to end an embryo’s life, but this study contradicts that narrative,” Donna Harrison, the director of research for the American Association of Pro-Life Obstetricians and Gynecologists—which was a plaintiff in last year’s Supreme Court case—told me in a statement. “Women deserve to be fully informed about how this drug works, as well as its risks.” (Until now, no evidence had indicated the drug’s abortifacient potential; at the dose approved for emergency contraception, there is still no evidence that Ella can disrupt an established pregnancy.)

[Read: Abortion pills have changed the post-Roe calculus]

The Gynuity study points to a possible role for ulipristal acetate as part of an abortion regimen, Kelly Cleland, the executive director of the American Society for Emergency Contraception, told me. But it doesn’t change what we know about its use for emergency contraception. For now, Ella remains on the market as just that.