U.S. government officials are putting an early end to a study testing an Eli Lilly antibody drug for people hospitalized with COVID-19 because it doesn’t seem to be helping them.

Independent monitors had paused enrollment in the study two weeks ago because of a possible safety issue. But on Monday, the National Institute of Allergy and Infectious Diseases, which sponsors the study, said a closer look did not verify a safety problem but found a low chance that the drug would prove helpful for hospitalized patients.

It is a setback for one of the most promising treatment approaches for COVID-19. President Donald Trump received a similar experimental, two-antibody drug from Regeneron Pharmaceuticals Inc. on an emergency basis when he was sickened with the coronavirus earlier this month.

In a statement Lilly notes that the government is continuing a separate study testing the antibody drug in mild to moderately ill patients, to try to prevent hospitalization and severe illness. The company also is continuing its own studies testing the drug, which is being developed with the Canadian company AbCellera.

Antibodies are proteins the body makes when an infection occurs; they attach to a virus and help it be eliminated. The experimental drugs are concentrated versions of one or two specific antibodies that worked best against the coronavirus in lab and animal tests.

Lilly and Regeneron have asked the U.S. Food and Drug Administration to grant emergency use authorization for their drugs for COVID-19 while late-stage studies continue. Lilly says its request is based on other results suggesting the drug helps patients who are not hospitalized, and that it will continue to seek the FDA’s permission for emergency use.