For months, outside researchers have been closely watching the development of antibody treatments. And top White House officials have been agitating for faster progress. At one point over the summer, Dr. Deborah L. Birx, the White House’s coronavirus response coordinator, lashed out at drug officials on Operation Warp Speed, the administration’s vaccine and therapy development program, for what she saw as sluggishness in setting up clinical trials for antibody treatments, according to one senior administration official.
The president and two of his top advisers — Mark Meadows, the White House chief of staff, and Jared Kushner, Mr. Trump’s son-in-law — have called Dr. Stephen M. Hahn, the F.D.A. commissioner, to press for speed in agency reviews, two other senior officials said.
Although neither Regeneron nor Eli Lilly has completed its antibody trials, evidence so far suggests that such treatments work best early in the course of the disease, before the virus has gained a foothold in the body.
The F.D.A.’s emergency authorization covers only a single antibody treatment developed by Eli Lilly, but the company is also developing a combination of two antibodies that has shown that it could be more effective in reducing the viral load in patients. In an early analysis, the two-antibody combination reduced the hospitalization of newly infected patients by about 5 percent. Eli Lilly has said it plans to apply for emergency authorization for the combination treatment this month, but will only have about 50,000 doses of that therapy before the end of the year.
Early evidence shows that the antibody treatments do not work well once people are sick enough to be hospitalized. Eli Lilly stopped giving its treatment to hospitalized patients in a government-run trial, because the company said it did not seem to be helping them. And Regeneron paused enrolling the sickest hospitalized patients in one of its trials.
In issuing the emergency authorization, the F.D.A. said that the treatment had not been shown to benefit hospitalized patients and that monoclonal antibodies like bamlanivimab might be associated with worse outcomes when given to hospitalized Covid-19 patients who need high-flow oxygen or mechanical ventilation.
This creates a problem for distributing the treatment, because it is only for people who are not hospitalized, yet those people must be infused intravenously by a health care provider. Getting it to the right people will require quick turnarounds in testing, as well as coordination among federal, state and hospital officials — many of the same challenges that have complicated the U.S. response to the pandemic.