Now that the FDA has granted emergency use authorization to Eli Lilly and Co.’s bamlanivimab, the company plans to manufacture up to 1 million doses of the therapy by year-end with worldwide distribution to mild to moderate COVID-19 patients ages 12 and older in early 2021.

The U.S. Department of Health and Human Services (HHS) said it will allocate the monoclonal antibody’s initial doses weekly to state and territorial health departments that will determine the health care facilities receiving it based on confirmed COVID-19 cases during the previous seven days. Hospitals and state health departments will enter their data into an HHS collection platform.

The U.S. government, which bought 300,000 doses for $375 million on Oct. 28 and could pay as much as $1.19 billion for 950,000 doses, has said U.S. patients will have no out-of-pocket costs though health care facilities may charge to administer the treatment.

There were doubters about bamlanivimab’s future right up until the FDA announcement. An NIH-sponsored phase III trial, ACTIV-3, testing LY-CoV555 and Veklury (remdesivir, Gilead Sciences Inc.) in hospitalized COVID-19 patients was paused and then halted after data showed it was unlikely to help advanced patients.

“We had low expectations for this approval, and certainly didn’t expect it to occur before Regeneron’s REGN-CoV2 doublet antibody,” wrote SVB Leerink analyst Geoffrey Porges on Nov. 10.

Regeneron Pharmaceuticals Inc. had hit the same wall as Lilly, a lack of success in treating hospitalized patients, when it paused recruitment in its study of monoclonal antibody REGN-COV2 of patients on high-flow oxygen and on mechanical ventilators. Porges wrote that Pfizer Inc. and partner Biontech SE, produced data Nov. 9 showing its vaccine, BNT-162b2, look like frontrunners with 90% protection in a phase III study that might muscle Regeneron aside.

“Lilly’s approval and Pfizer’s efficacy mean that REGN is likely to capture less share, of a smaller market than we had expected,” Porges wrote.

The FDA authorization is based on Lilly’s phase II Blaze-1 study, a randomized, double-blind, placebo-controlled investigation of outpatients with mild to moderate COVID-19. Viral load limits were reduced, according to the data, along with rates of symptoms and hospitalization.

Lilly continues to test bamlanivimab in Blaze-1 and Blaze-2, a study evaluating its use for the prevention of COVID-19 in residents and staff at long-term care facilities. In addition, bamlanivimab is being tested in the NIH-led ACTIV-2 study of ambulatory COVID-19 patients. Overall, about 1,000 trial participants have been dosed with bamlanivimab alone or in combination with a second Lilly antibody, etesevimab (LY-CoV016).

The authorization comes with limitations. Bamlanivimab, to be administered intravenously to individual patients as a single dose, is not for patients hospitalized with COVID-19 or those requiring oxygen therapy because the therapy has yet to prove beneficial for those groups. Matter of fact, the FDA continued, monoclonal antibodies “may be associated with worse clinical outcomes” when administered to hospitalized COVID-19 patients needing high-flow oxygen or mechanical ventilation. The FDA also warned about hypersensitivity that includes anaphylaxis and infusion-related reactions in patients.

Lilly also noted that treatment benefits have yet to be found in hospitalized COVID-19 patients.

To receive Lilly’s treatment, patients must test positive through direct SARS-CoV-2 viral testing, they must weigh at least 88 pounds and be at high risk to progressing to severe COVID-19 or hospitalization or both. Even those at higher risk, such as those ages 65 or older or those with certain chronic medical conditions, are approved for the treatment. The infusion process lasts about an hour and would possibly be followed by an observation period.

Lilly stock (NYSE:LLY) rose $4.23 on Nov. 10, to close at $146.56.