More than 300 reproductive health researchers urged the Supreme Court to follow the science when they hear arguments on mifepristone, a drug used in medication abortion that is under attack by Republican lawmakers and conservative courts.

While detractors have cast doubt on mifepristone’s safety and effectiveness, the researchers said there is “ample scientific evidence” to support its widespread availability under guidelines set out by the Food and Drug Administration.

Separately, a group of 263 members of Congress submitted a brief imploring the high court to respect the FDA’s authority — given by Congress — to regulate drugs like mifepristone.

“This Court should not allow the politics of abortion to obscure the clear, abundant, and plainly sufficient scientific record supporting FDA’s decision-making in this case,” the scientists’ brief said.

Those who signed the statement included medical professors, medical doctors, principal researchers, postdoctoral researchers and others hailing from a variety of top institutions, including the University of California, Los Angeles, Brown University, Rutgers University, Johns Hopkins University and the Guttmacher Institute.

Led by lawmakers including Sen. Patty Murray (D-Wash.), the congressional brief argued that the case against mifepristone stepped on the toes of Congress.

“While Congress permitted some judicial review of FDA’s approval decisions, it did not invite federal courts to substitute their judgment for the expert conclusions of FDA’s scientists,” said the brief, which was signed by 50 senators and 213 members of the House of Representatives.

Since the FDA approved mifepristone in 2000, it has gradually become easier to obtain. Currently, a pregnant person may get a prescription in person or virtually, and the drug may be dispensed in person or by mail.

Most abortions in the United States are done by medication, usually a combination of mifepristone and another drug called misoprostol.

The Supreme Court is expected to hear arguments March 26 from both the Biden administration and the drug manufacturer. The justices will mull limitations that a federal appellate court would have imposed on the drug’s availability. The high court paused enforcement of the appellate ruling while it considers the issue.

The appellate ruling would shorten the time frame that mifepristone can be used in a pregnancy from 10 weeks to seven weeks, and would eliminate access by mail.

But medical experts have long said the drug is safe. More than 5 million people have used mifepristone in the U.S. since 2000.

The current threat to mifepristone’s availability began with a lawsuit in Texas, which landed in the courtroom of U.S. District Judge Matthew Kacsmaryk, a right-wing judge who said the drug’s original approval should be revoked. The case was appealed to the Fifth Circuit, one of the most conservative courts in the nation, which said the drug’s approval could stand with more restrictions.

The Supreme Court is expected to rule by the end of June.