But although both companies have reported promising early results, clinical trials are still underway. Although Mr. Trump credited the Regeneron treatment with having improved his illness, there is no way to know if a drug is safe and if it works without testing it in large groups of people, some who receive the drug, and some who get a placebo.
Regeneron and Eli Lilly have said the therapies could be available before the end of the year. Some medical experts have seen the therapies as a sort of bridge until vaccines are available — the infusion of antibodies could be given to people who have been exposed to the virus in order to prevent infection, as well as to people who are still early in the course of the disease.
In his video, Mr. Trump suggested that the treatments could soon be authorized for emergency use. “We have to get them done, we have to get them approved,” he said. But that is a potentially risky move because it could allow the treatments to become widely used before they have been proven. Broader access to the drugs could then jeopardize enrollment in clinical trials, because people may be reluctant to participate if there is a chance they could receive a placebo.
The president also used the video as another opportunity to push for the emergency approval of a vaccine before the election, even though the Food and Drug Administration has issued guidelines to companies that would mean meeting such a deadline is not possible. “I think we should have it before the election, but frankly, the politics gets involved, and that’s OK,” he said.
A handful of vaccine makers are testing their candidates in large clinical trials and have said they could have an answer before the end of the year, but they have also made an unusual pledge to not bring their vaccines to market before they are thoroughly vetted.
Monoclonal antibodies like the ones that Regeneron is developing are difficult and expensive to manufacture, and some have raised questions about whether the companies will be able to make enough to meet global demand if they are proven to work. In August, the company announced it was teaming up with a larger company, Roche, to ramp up production.
The video was not the only way Mr. Trump tried on Wednesday to put the best spin on his illness.
In midafternoon, he resumed working in the Oval Office, defying the aides who had hoped he would remain in his private quarters in the White House or a work space specially set up him for him because he is sick.