WASHINGTON (AFP, BLOOMBERG) - US President Donald Trump is receiving an experimental treatment of synthetic antibodies for Covid-19, his doctor said on Friday (Oct 2), and is "fatigued but in good spirits".
Trump received a single dose of Regeneron's antibody cocktail, according to a letter issued by White House physician Sean Conley.
The treatment is undergoing clinical trials but has not received any form of regulatory approval.
"He's being evaluated by a team of experts, and together we'll be making recommendations to the President and First Lady in regards to next best steps," Conley said.
He said First Lady Melania Trump, who is also infected, "remains well with only a mild cough and headache".
Trump - who has repeatedly cast doubt on the seriousness of the pandemic - first announced in an overnight tweet that he and First Lady Melania Trump, 50, had tested positive and were going into quarantine.
Earlier this week, Regeneron announced results from one of its early-stage trials which showed its drug, which is infused intravenously, reduced viral load and recovery time in non-hospitalised Covid-19 patients.
"We have begun discussing our findings with regulatory authorities while continuing our ongoing trial," said George Yancopoulos, the company's president and chief scientific officer on Tuesday.
The US biotech firm is concurrently running late-stage trials for hospitalised Covid-19 patients and for the drug's potential use as a prophylaxis.
Antibodies are infection-fighting proteins made by the immune system that can bind to particular structures on the surfaces of pathogens and prevent them from invading cells.
Vaccines work by teaching the body to make its own antibodies, while scientists are also testing ready-made antibodies from the blood of recovered patients, called convalescent plasma.
But it is not possible to make convalescent plasma a mass treatment.
Researchers can also comb through the antibodies produced by recovered patients and select the most effective out of thousands, and then manufacture it at scale.
Regeneron's experimental Covid-19 drug, called REGN-COV2, is a combination of two antibodies, referred to as a "cocktail".
The idea is it will have a better chance at working if the virus mutates in order to evade the blocking action of a single antibody.
Last year, a triple-antibody cocktail developed by Regeneron was shown to be effective against the Ebola virus.
Trump and his wife have been in isolation at the White House since his diagnosis, which he announced after Bloomberg News reported that one of his closest aides, Hope Hicks, had tested positive for coronavirus infection.
Conley's statement was the first update from Trump's doctor since early Friday morning.
The president has not tweeted or made any public statement since announcing his infection at 12.54am in Washington.
Trump learned of Hicks's positive test on Thursday morning but continued with his planned schedule for the day, including a fund-raiser at his Bedminster, New Jersey golf resort that raised US$5 million for his campaign, according to people familiar with the matter.
Trump and Hicks had been in close contact in the days before her diagnosis. She travelled with him to the presidential debate in Cleveland on Tuesday and to campaign events in Minnesota on Wednesday.
Hicks tested negative for infection Wednesday morning, then fell ill in Minnesota and was isolated on the flight back to Washington aboard Air Force One, according to people familiar with the matter.