WASHINGTON — The U.S. government has agreed to buy initial doses of an experimental COVID-19 antibody drug from Eli Lilly that patients could receive if federal regulators allow it on an emergency basis.

Lilly has asked the U.S. Food and Drug Administration to allow use of the drug in mild to moderately ill patients, based on partial results from a mid-stage study suggesting it may help them clear the virus sooner. There were hints the drug might help avoid hospitalization, but more study is needed.

Under the agreement, the government will spend $375 million to buy 300 million vials of the drug. How many doses that would provide is unclear. Each vial contains 70 milligrams and that dose proved ineffective in the early results. It took four times that amount — 2,800 milligrams — to show any effect.

Earlier this week, the government stopped a study of Lilly’s drug in hospitalized patients after it seemed the drug was not helping those more seriously ill patients.

Regeneron Pharmaceuticals Inc. also is seeking emergency use for its experimental two-antibody treatment. President Donald Trump received it when he was ill with the coronavirus earlier this month.