(Reuters) - U.S. hospitals, weighing high demand and tight supplies, said they may limit use of a new Eli Lilly and Co LLY.N antibody 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. The treatment, bamlanivimab, was given U.S. emergency use authorization (EUA) last week by the Food and Drug Administration for helping newly-diagnosed, high-risk patients avoid hospitalization. “There will be a lot of pressure on physicians,” said Dr. Adarsh Bhimraj, an infectious disease specialist at the Cleveland Clinic and chair of the Infectious Diseases Society of America’s guidelines panel, which is still discussing its recommendations for the drug. President Donald Trump has touted experimental antibody drugs after being treated with a similar therapy from Regeneron Pharmaceuticals Inc REGN.O during his own bout with COVID-19. The federal government has paid $1,250 per dose for 300,000 doses of bamlanivimab, which experts estimate may only be enough for one weeks’ worth of Americans becoming infected, based on the FDA label identifying appropriate patients. The United States on Sunday crossed 11 million total coronavirus infections just a little over a week after hitting the 10 million mark since the pandemic began. Medical groups and hospitals said they are working to establish criteria for which patients are likely to benefit most from the drug, which consists of manufactured copies of an antibody made by the human body to fight COVID-19. “Otherwise, we will be out of drug real soon,” said Dr. Howard Huang, a lung specialist at Houston Methodist. The FDA authorized bamlanivimab for patients over age 65 recently diagnosed with mild-to-moderate COVID-19 and patients with obesity, diabetes, or another risk factor. The agency said the drug should not be used in hospitalized patients. “There may need to be some sort of composite score” to select patients, Huang said. “Maybe we would use it for someone who has cardiovascular disease, and a history of stroke and is older?” Dr. Neha Nanda, medical director of infection prevention with Keck School of Medicine at the University of Southern California in Los Angeles said “more conservative criteria” is needed. “One group you could exclude is someone who has an antibody test that is positive,” she said. “I think we may need to do that.” Regeneron has said its experimental COVID-19 antibody cocktail has shown the most benefit in patients who had not mounted their own immune response prior to treatment. The company is also seeking an EUA. Despite the FDA’s clearance of Lilly’s drug - based on published findings from a small mid-stage study - experts said they would like to see more clinical trial data. The drug, given as a one-time infusion, is initially being distributed only to hospitals. Some were already set up to treat trial patients, while others said they are working on logistics. The United States has the option to buy another 650,000 doses, but hospitals expect the drug will eventually become a commercial product. Eli Lilly officials did not respond to requests for comment on pricing plans.