The U.S. government will pay Eli Lilly $375 million to buy 300,000 vials of the company’s experimental coronavirus drug, securing an initial supply of the antibody treatment as cases of COVID-19 rise dramatically across the country. Earlier this month, Lilly requested an emergency clearance from the Food and Drug Administration for use the drug, dubbed bamlanivimab. Early study results showed treatment helped lower virus levels in people with mild or moderate COVID-19, and suggested the drug may reduce the risk of hospitalization. This week, however, researchers leading a government-run study of bamlanivimab in patients already hospitalized with COVID-19 determined treatment was unlikely to help and recommended discontinuing study of the drug in that setting. Lilly is not seeking approval of the drug for use in hospitalized patients.

With the Lilly deal, the U.S. government nearly doubles the supply of antibody drugs for COVID-19 that it can tap. Earlier agreements with Regeneron and AstraZeneca, worth close to $1 billion combined, laid claim to as many as 400,000 doses of their experimental antibody drugs, depending on how they’re used in treatment.

Antibody drugs are powerful mimics of the body’s own immune defenses, designed to latch onto and neutralize invading SARS-CoV-2 virus. In theory, they could work both as a short-term preventive therapy and as treatment for existing infections.

Early results from Lilly and Regeneron, which are the furthest along in a field of developers that includes AstraZeneca and Vir Biotechnology, showed treatment with either antibody drug could clear out the virus in people with mild COVID-19. More encouragingly, the early evidence pointed to — but did not prove — more compelling benefits, such as a lower risk of hospitalization or earlier alleviation of disease symptoms.

On the back of those findings, both companies quickly submitted requests to the FDA for emergency use authorizations, each focusing on people with COVID-19 who, for different reasons, may be at higher risk of more severe disease.

Despite the drugs’ promise, however, further evidence is needed to conclusively say whether or not they actually help. The recent negative finding in a National Institutes of Health-sponsored study of Lilly’s drug, meanwhile, suggests antibody treatment may not be effective in sicker patients already dealing with later complications of infection.

And both Lilly’s and Regeneron’s therapies are given via infusion, making early treatment of people who are less sick a particular challenge and potential transmission risk.

In a statement, Lilly acknowledged the hurdles for recently diagnosed COVID-19 patients to access treatment, noting that it’s working with the Trump administration to identify and create locations where people could receive an infusion without going to a hospital or clinic where they could transmit the virus to others.

Per the deal signed with the U.S. government, Lilly will provide the promised 300,000 vials within the first two months following grant of an emergency use authorization by the FDA. The Trump administration also secured an option to buy another 600,000 vials through June 30, 2021.

Lilly expects to have manufactured 1 million doses of the drug through the end of this year, with supply ramping up in 2021.

But, with available doses limited, Lilly said it would only commit to supply a few months’ worth of its drug in agreements with governments, prioritizing those hardest hit by COVID-19. Right now, Lilly noted, that includes the U.S., where cases have climbed to new heights, surpassing 70,000 a day.

For wealthier counties like the U.S., Lilly will charge $1,250 per vial for bamlanivimab, with tiered pricing based on nations’ ability to pay. Doses bought by the U.S. government would be provided to people in the U.S. for free, according to Lilly, although healthcare providers may charge for administration.

The drugmaker expects to earn a “modest financial return” at those prices through the end of next year.

Gilead’s approved COVID-19 drug Veklury, by comparison, costs between $2,340 and $3,120 per five-day treatment course.

Lilly is also studying another antibody drug that it’s testing in combination with bamilanivimab. Initial results suggested the drug pairing may offer additional benefits. The U.S., however, did not contract with Lilly to receive supplies of the partner antibody, developed by China’s Junshi Biosciences.