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The US government is betting big on an experimental antibody cocktail from AstraZeneca that could prevent COVID-19 for up to a year after a single injection. The drugmaker has received about $486 million to test it in two Phase 3 clinical trials.
In one of the trials, about 5,000 healthy people will be given the antibody treatment, AZD7442, and followed for 12 months to see if it prevents infection. In the other trial, about 1,100 people who recently contracted the virus or are at high risk of exposure will receive the treatment to see if it prevents infection and illness.
The funding comes from the Biomedical Advanced Research and Development Authority and the Department of Defense, and it includes a supply of up to 100,000 doses of the antibody. The first shipments could arrive by the end of the year. The US government could buy another 1 million doses in 2021.
In July, the two agencies paid Regeneron Pharmaceuticals $450 million for a preorder of the firm’s own antibody cocktail for treating COVID-19. President Donald J. Trump was given an experimental injection after testing positive for the coronavirus earlier this month. Soon after, Regeneron applied for emergency use authorization (EUA) of its antibodies.
Eli Lilly and Company, which is developing its own monoclonal antibodies for COVID-19, applied for an EUA too, but its clinical trial was halted on Oct. 13 due to a potential safety concern. No details are available at this time.
AZD7442 is a combination of two monoclonal antibodies that target different surfaces on SARS-CoV-2, the virus that causes COVID-19. The antibodies were discovered by scientists at the Vanderbilt Vaccine Center who screened hundreds of antibodies from the blood of four people who had recovered from COVID-19 in early spring.
AstraZeneca licensed the antibodies from Vanderbilt in June, and introduced a trio of amino acid mutations to the back end of each antibody—the Fc region—to extend its half-life. That tweak, called the YTE mutation, prevents proteins known as Fc receptors from recognizing the antibodies and removing them from circulation, says Robert Carnahan, associate director of the Vanderbilt Vaccine Center.
Scientists at AstraZeneca have already tested the YTE mutation in other experimental antibodies, including one for respiratory syncytial virus called MEDI8897. In one clinical study, that antibody’s half-life was about 9–10 weeks, compared with the expected 3–4 weeks for antibodies without the YTE mutation. For its experimental COVID-19 therapy, AstraZeneca expects that the levels of antibodies circulating in the body could prevent infection for 6–12 months.
If the trials are successful, the antibodies could provide an alternative to vaccines for preventing coronavirus infections. Antibodies would be especially useful for high-risk populations, such as health-care workers and people who live and work at nursing homes, Carnahan explains. For instance, if one person in a nursing home tests positive for the coronavirus, residents and employees could be given the antibody to stop infections early or even prevent them altogether.
It can take a few weeks or more for vaccines to induce protective levels of antibodies, Carnahan says. In contrast, “an antibody therapy is effective almost immediately upon injection.”