President Trump Received Regeneron Experimental Antibody Treatment

President Trump has received a dose of an experimental antibody cocktail being developed by the drug maker Regeneron, in addition to several other drugs, including zinc, vitamin D and the generic version of the heartburn treatment Pepcid, according to a letter from his doctor that was released by the White House Friday afternoon.

Mr. Trump and the first lady, Melania Trump, announced early Friday morning that they had . The president has a low-grade fever, nasal congestion and a cough, according to two people close to Mr. Trump.

, Mr. Trump’s doctor, Dr. Sean P. Conley, said “he completed the infusion without incident” and that he “remains fatigued but in good spirits.”

There are no approved treatments for Covid-19, but the Regeneron treatment is one of the most promising candidates, along with another antibody treatment developed by Eli Lilly. Both are being tested in patients around the country. Initial results have suggested that they can reduce the level of the virus in the body and possibly shorten hospital stays — when they are given early in the course of infection.

the malaria drug hydroxychloroquine in the hopes that it could prevent infection. The Food and Drug Administration authorized hydroxychloroquine for emergency use this spring, its approval after concluding that the drug’s potential benefits did not outweigh the risks.

Mr. Trump has also enthusiastically endorsed the use of convalescent plasma and the treatment for emergency use even though there is still not good evidence that it works. that injecting a disinfectant like bleach could help combat the virus, although later said he was joking.

Other treatments — , and remdesivir, an antiviral drug developed by Gilead — have been shown in clinical trials to help patients with Covid-19 who are sick enough to be hospitalized. Neither drug has gone through the rigorous F.D.A. approval process to determine that it is safe and effective, although dexamethasone is widely available for other uses, and remdesivir .

as for Covid-19, although none have been definitively proven to work.

Dr. Clifford Rosen, a professor of medicine at Tufts and an associate editor at the New England Journal of Medicine, said there are no rigorous clinical trials showing vitamin D, zinc or famotidine help fight the virus.

Mr. Trump in 2018 signed the Right to Try law, which allows patients and their doctors to directly request an experimental treatment from a company, without first seeking approval from the F.D.A., which typically approves the vast majority of such requests. The Right to Try law is rarely used, however, with most doctors and hospitals preferring to use the existing process of seeking company and then agency approval.

Some ethics experts said it was not surprising that Mr. Trump was given an experimental drug, given that it has passed safety trials.

enrolling participants in clinical trials that used a placebo.

On Tuesday, that its treatment, a cocktail of two antibodies, hastened recovery time and reduced the amount of virus in the nasal cavities of a small number of volunteers in its ongoing study.

The new results were from a study of 275 volunteers who were treated after being diagnosed with Covid-19. Those who were not making their own antibodies at the start of the trial benefited the most, Regeneron reported. Their symptoms resolved in an average of 6 to 8 days, compared with 13 days in those who received a placebo.

The dose that Mr. Trump received is the higher of two doses that Regeneron is testing in its trial of outpatients with Covid-19.

Despite their early promise, monoclonal antibodies 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.

it was teaming up with a larger company, Roche, to ramp up production.

Maggie Haberman and Michael D. Shear contributed reporting.