Dec 2 (Reuters) - Eli Lilly and Co said on Wednesday the U.S. government has purchased 650,000 additional doses of its COVID-19 antibody drug for $812.5 million.

The doses will be delivered through Jan. 31, with at least 350,000 delivered in December, the company said.

The experimental drug has been authorized by the U.S. Food and Drug Administration for emergency use for helping newly-diagnosed, high-risk patients avoid hospitalization, and the government bought 300,000 doses in October.

The new purchase is part of a U.S. government deal to secure nearly 1 million doses of Lilly's bamlanivimab, a treatment similar to Regeneron Pharmaceuticals Inc's COVID-19 antibody therapy that U.S. President Donald Trump received in October during his illness.

The treatments belong to a class of drugs called monoclonal antibodies that are manufactured copies of antibodies created by the body to fight against an infection.

U.S. hospitals said in November they may limit use of Lilly's drug to COVID-19 patients with multiple risk factors for serious illness or to those whose immune systems have not begun to fight the infection due to high demand and tight supplies.

Medical groups and hospitals are working to establish criteria for patients likely to benefit most from the drug, which is given as a one-time infusion.

Earlier in the day, CVS Health Corp said it would administer Lilly's treatment to COVID-19 patients in their homes and in long-term care facilities through a U.S. government-backed pilot project.

Lilly said on Wednesday it expected to manufacture up to one million doses of bamlanivimab by the end of 2020 for use around the world through early next year. (Reporting by Dania Nadeem in Bengaluru; Editing by Sriraj Kalluvila)