U.S. President Donald Trump was hospitalized for three days earlier this month after experiencing symptoms of COVID-19. He received several treatments for the disease. One was an experimental antibody drug from the American biotechnology company Regeneron Pharmaceuticals.

On Sunday, Trump told Fox News "The antibody kind of thing that I took, I felt really good almost after taking it. ... I know people call it a therapeutic, but, to me, it's a cure, OK? To me, it's a cure." The president added that he wanted the treatment offered to coronavirus patients "immediately."

But not so fast!

Leonard Schleifer is head of Regeneron. He told CBS News, "The president's case is a case of one, and that's what we call a case report, and it is evidence of what's happening, but it's kind of the weakest evidence that you can get."

Trump is among fewer than 10 people who received the antibody drug under "compassionate use" rules. He was not taking part in a study on the drug's safety and effectiveness. The U.S. Food and Drug Administration (FDA) permits use of experimental treatments in seriously ill patients when no other treatments are available.

Even if it is not a cure like Trump said, Regeneron and drug-maker Eli Lilly are now asking the FDA to permit emergency use of their antibody drugs in patients with COVID-19.

How do they work?

Antibodies are proteins the body makes when an infection occurs. They connect to a virus and help kill the harmful bacteria.

Vaccines make the body think it has an infection and, in turn, produce antibodies to fight it. But it can take several weeks after a vaccine or natural infection for the body to make the most effective antibodies.

The experimental drugs from Regeneron and Eli Lilly are very strong antibodies. They were created in laboratories and are currently being tested. The treatments, in theory, start helping COVID-19 patients right away.

How do the drugs differ?

Regeneron's REGN-COV2 treatment combines a genetically-engineered antibody and a second antibody -- one from recovered COVID-19 patients.

The company used this process to manufacture a successful antibody treatment for Ebola virus disease. This method has also been used to develop drugs to treat other viruses such as HIV, the cause of AIDS.

Eli Lilly is testing two antibody treatments. One involves a single antibody, called LY-CoV555. The second treatment combines that antibody with an antibody called LY-CoV016. It is meant for higher risk patients.

Lilly said early results of a study showed the treatment reduced hospital emergency room visits for persons with mild or moderate forms of COVID-19. It said the treatment also reduced symptoms of the disease, the amount of the virus and length of hospital stays for such patients.

Lilly and Regeneron have only reported partial results of their studies. Information from the trials has yet to be published or seen by independent scientists.

On October 13, Lilly announced that it temporarily stopped the combination treatment trials for safety reasons. Its treatment is similar to the combined antibody treatment from Regeneron.

When might they be available?

During public health emergencies, the FDA can approve drugs to treat COVID-19 patients based on a lower standard of evidence that is normally required. Both Eli Lilly and Regeneron asked the FDA last week for emergency authorization.

On March 20, the FDA approved the malaria drug hydroxychloroquine for emergency use in patients with COVID-19. By June 15, the agency withdrew the emergency use authorization and warned against its use.

At this time, only remdesivir, a medicine developed by Gilead Sciences, has been approved for the treatment of hospitalized patients with COVID-19. Remdesivir appeared to help patients with moderate signs of COVID-19 recover faster after a five-day treatment when compared to those receiving other treatments.

A report on the drug's effectiveness was published in The Journal of the American Medical Association in August.

I'm Jonathan Evans.

Hai Do wrote this story for Learning English. George Grow was the editor.

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symptom - n. a change in the body which indicates that a disease is present

therapeutic - adj. producing good effects on your body or mind

ill - adj. not well or unhealthy

occur - v. happen

standard - n. a level of quality that is considered acceptable

authorization - n. official approval for something