By Joseph Walker

Regeneron Pharmaceuticals Inc.'s Covid-19 antibody drug was authorized Saturday by U.S. health regulators, the second cleared this month to treat patients who aren't hospitalized but are at high risk of developing severe disease.

The Food and Drug Administration cleared the antibody drug cocktail for use treating mild to moderate Covid-19 patients 12 years of age and older, including people older than 65 years.

Regeneron's drug combines two lab-made antibodies designed to latch onto the novel coronavirus and prevent it from replicating and hijacking human cells. The treatment is still being tested in clinical trials, after being developed by Regeneron scientists in Tarrytown, N.Y., earlier this year.

In October, it was one of three pharmaceutical treatments given to President Trump for treatment of Covid-19. Mr. Trump later attributed his recovery. "They gave me Regeneron, and it was like, unbelievable. I felt good immediately," he said.

The FDA said it authorized the drug's emergency use, a kind of clearance the agency has been using during the pandemic to speed up access to medicines.

The FDA said its authorization was based on a study of about 800 people. In the study, 3% of subjects taking Regeneron's drug and who were at high risk of severe disease had to be hospitalized or visit emergency rooms, compared with 9% of patients who received a placebo.

"The emergency authorization of these monoclonal antibodies administered together offers health care providers another tool in combating the pandemic," Patrizia Cavazzoni, M.D., acting director of the FDA's Center for Drug Evaluation and Research, said in a statement.

Earlier this month, the FDA issued an emergency authorization for an antibody drug made by Eli Lilly & Co. for a similar set of patients.

The FDA didn't authorize the treatments for hospitalized patients. In the sickest patients, those requiring high-flow oxygen support or mechanical ventilation while hospitalized, monoclonal antibodies such as Regeneron and Eli Lilly's drugs could make patients sicker, the FDA warned.

The Eli Lilly and Regeneron drugs are the first to show promising results in treating patients who haven't yet been hospitalized, filling a big hole in treatment.

Previous drugs cleared for Covid-19 use, such as Gilead Sciences Inc.'s remdesivir, were authorized for hospitalized patients.

Lilly and Regeneron were among the first to set out to develop antibody drugs for Covid-19 after the virus's genetic sequence was published in January. Other companies working on the therapies include AstraZeneca PLC, GlaxoSmithKline PLC and Vir Biotechnology Inc.

Antibodies are soldiers in the body's immune system that help it fight off pathogens. Lab-made antibody drugs mimic their natural counterparts.

Lilly's antibody drug was derived from antibodies isolated from the blood of a patient who recovered from Covid-19. Regeneron's drug combines an antibody from a recovered patient and one generated by mice with genetically modified immune systems.

The drugs are made from living cells, a process that is more complicated and expensive than making pills. Both companies say shortages are likely given the expected demand.

Regeneron has agreed to provide the first 300,000 doses to the U.S. government as part of a $450 million contract signed in July.

Regeneron said it would have enough doses of its drug to treat 80,000 patients by the end of November, an additional 120,000 doses in the first week of January, and another 100,000 doses by the end of January 2021.

The drug cocktail contains antibodies named casirivimab and imdevimab, a combination that formerly went by the code name REGEN-COV2.

"Demand may exceed supply initially, making it even more critical that federal and state governments ensure REGEN-COV2 is distributed fairly and equitably to the patients most in need," Regeneron Chief Executive Leonard Schleifer said in a statement.

An FDA fact sheet on the drug says it may be ineffective against strains of the coronavirus that are resistant to the antibodies.

"We are encouraged that no variants resistant to the cocktail were identified in the clinical trial analyses to date, which is consistent with our preclinical findings," Regeneron Chief Scientific Officer George D. Yancopoulos said in a statement.

Write to Joseph Walker at joseph.walker@wsj.com

(END) Dow Jones Newswires

11-21-20 2126ET