The drug, Makena, is a synthetic version of the hormone progesterone, which is needed to maintain a pregnancy. It’s the only drug with FDA approval to reduce the risk of premature birth.

The removal announcement Tuesday from Covis Pharma comes roughly four years after Makena failed to show a benefit in helping mothers carry pregnancies to term.

Since then the Food and Drug Administration has been moving to get the drug off the market, though Covis has repeatedly appealed for more time to conduct additional research. The injectable drug has become a symbol for the challenges the FDA faces to withdraw a medication when the manufacturer won’t do so voluntarily.

Indeed, the timing of the drug’s removal remains uncertain. Covis, based in Switzerland, said in its release that FDA regulators rejected its proposal to wind down the drug’s use over several months.

The company said that extended off-ramp would give women who are still receiving the drug time to finish their course of treatment, which involves weekly injections starting after 16 weeks of pregnancy.

But the FDA made clear it would continue its process to force the drug’s removal on its own terms, according to the company. In a separate filing Wednesday, the agency’s drug regulators recommended making the withdrawal “immediately effective.” The agency noted there’s no indication of “harm from discontinuing Makena, such as signs or symptoms of withdrawal.”

FDA Commissioner Robert Califf is expected to soon decide on the drug’s fate, in consultation with the agency’s top scientist.

Covis made its proposal to the FDA following an October public meeting at which outside advisers overwhelmingly concluded that Makena hasn’t been shown to work and should have its approval revoked. Despite hours of presentations and debate, the panel was unconvinced by arguments from Covis that the drug could be useful for a subgroup of women.

Such hearings are extraordinarily rare and occur only after a drugmaker rejects initial FDA requests to pull its drug.

“While we stand by Makena’s favorable benefit-risk profile, including its efficacy in women at highest risk of preterm birth, we are seeking to voluntarily withdraw the product and work with the FDA to effectuate an orderly wind-down,” said Raghav Chari, Covis’ chief information officer, in a statement.

The company added that it “remains ready to work cooperatively with the agency,” to remove the drug, despite disagreement on the timeframe.

About 10% of U.S. births come too early, before 37 weeks, raising the risk of serious health problems and even death in infants. The problem occurs at higher rates among Black women.

The FDA granted Makena accelerated approval in 2011 based on a small study in women with a history of early deliveries. The expedited approval was conditioned on a larger follow-up study to confirm whether the drug resulted in healthier outcomes for babies.

In 2019, results from that 1,700-patient international study showed the drug neither reduced premature births — as originally thought — nor resulted in healthier outcomes for infants.

Despite those results, reproductive specialists — including members of the American College of Obstetricians and Gynecologists — have argued for keeping the decade-old drug available while more research is done.

The group said Wednesday its current guidelines will remain in effect until FDA makes a final decision.

“It is critical that other effective interventions be identified to prevent recurrent preterm birth for the health and well-being of our patients and their families,” the group said in a statement.