No FDA-Approved Drug Stops Preterm Labor: a Vanderbilt Screen of All 1,191 Approved Drugs Landed on an Asthma Steroid

When a woman arrives on a labor floor at twenty-eight weeks with contractions that will not stop, the obstetrician reaching for something to slow them is, in every case, reaching for a drug approved to treat something else. Terbutaline was cleared for asthma, nifedipine for blood pressure, indomethacin for pain. Magnesium sulfate, the workhorse, was never approved as a labor drug at all. The FDA has never approved a medicine in the United States for the single job of stopping preterm contractions, and the profession has spent decades borrowing from other shelves and hoping it holds.

So a Vanderbilt team did not run a clever trial of one promising molecule. They searched the whole cabinet. Shajila Siricilla and Jennifer Herington, both in the pediatrics department at Vanderbilt University Medical Center, screened all 1,191 FDA-approved drugs for the ability to quiet uterine muscle while mostly sparing the smooth muscle in blood vessels, then filtered the survivors for safety and plausibility. Several cleared the bar. The one they named, in work published September 23 in Science Translational Medicine, was ciclesonide, a steroid inhaler approved for asthma and allergy symptoms.

The appeal, as the researchers describe it, is a possible two-for-one. Because ciclesonide is a corticosteroid, Herington raised the “intriguing possibility” that a single repurposed drug “could ultimately have relevance both before and after preterm birth,” quieting the contractions on the way in and supporting the newborn on the way out. On paper that is elegant. It is also, and the study says so plainly, entirely preclinical. The screen ran in cells and human uterine tissue, not in pregnant women. “Our findings do not mean that these drugs are ready to be used clinically for preterm labor,” Herington said in the university’s own announcement, “rather, they identify promising candidates for further development.” That is a rare bit of restraint from a corresponding author with a result to promote.

The restraint is earned, because this is the exact disease area where the last drug everyone got excited about turned out not to work, and it took the FDA twelve years to say so out loud.

Makena, the brand name for 17-alpha hydroxyprogesterone caproate, won accelerated approval in 2011 to prevent recurrent preterm birth, a related but separate problem from stopping labor once it has started. The approval rested on a single 2003 trial in which delivery before thirty-seven weeks fell from 54.9 percent on placebo to 36.3 percent on the drug. Impressive numbers. The bargain of accelerated approval is that the sponsor then owes a confirmatory trial, and when that trial, PROLONG, finally read out, it showed no benefit over placebo on the outcomes that mattered. The 2003 trial said the drug worked. PROLONG did not.

An FDA advisory committee voted to pull the drug in 2019. The agency did not formally withdraw it until April 2023. In the years between, Covis Pharmaceuticals, which had bought the franchise, fought the withdrawal with a thirty-page rebuttal carrying a hundred and forty footnotes, and the weekly injections went on even though the confirmatory evidence was already in. Medicaid and Medicare spent more than $700 million on it between 2018 and 2021, the years when that evidence was pointing the other way.

Set against that record, a computational sweep of drugs that already exist is not a lesser kind of science. It is arguably the more honest kind, because repurposing an approved medicine means the human safety data is already on file, the manufacturing already runs, and no patient is the first person ever to take it. The catch is the same one that sank Makena. A drug that relaxes uterine tissue in a dish has cleared the lowest bar in drug development, not the highest, and between this screen and a woman on a labor floor sit exactly the trials that Makena passed on a surrogate and then failed on the real thing.

Herington has said the study’s real contribution is the method, a systematic way to surface safer candidates from drugs already on pharmacy shelves, and on that modest claim she is almost certainly right. Whether ciclesonide is one of them is a question only a trial can settle. The one drug the FDA approved anywhere near this problem, it later clawed back. A search that starts from that fact, rather than around it, is at least starting in the right place.

Sources

1. Vanderbilt Health News – study identifies existing drugs with potential to improve preterm-labor outcomes (Sept 23, 2026)
2. News-Medical – screening approved medicines reveals potential treatments for preterm labor (Sept 23, 2026)
3. American Journal of Obstetrics & Gynecology (via PMC) – the withdrawal of 17-alpha hydroxyprogesterone caproate: PROLONG, the 2011 to 2023 timeline, and the $700 million spend
4. Science Translational Medicine – Siricilla, Herington et al., screen of 1,191 FDA-approved drugs for uterine-selective tocolytic activity (2026), DOI 10.1126/scitranslmed.aeb2020
5. FDA Drug Safety Communication – new warnings against the use of terbutaline to treat preterm labor (2011)