US President Donald Trump walks to board Marine One to depart from the White House in Washington DC, Jan 9, 2020. (TING SHEN / XINHUA)

WASHINGTON - US President Donald Trump is taking remdesivir, a COVID-19 drug manufactured by biopharmaceutical company Gilead Sciences, as a treatment, White House physician Sean Conley said on Friday.

"Going well, I think! Thank you to all. LOVE!!!" Trump tweeted from Walter Reed on Friday night

Conley said in a memo that Trump, who is staying at Walter Reed National Military Medical Center in Bethesda, Maryland, "has completed his first dose and is resting comfortably."

The doctor said he recommended moving the president to Walter Reed on Friday afternoon "for further monitoring" in consultation with specialists from the military hospital and Johns Hopkins University. The White House said Trump will be staying in the facility "for a few days".

"This evening I am happy to report that the President is doing very well," Conley continued. "He is not requiring any supplemental oxygen, but in consultation with specialists we have elected to initiate remdesivir therapy."

"Going well, I think! Thank you to all. LOVE!!!" Trump tweeted from Walter Reed on Friday night.

The president tweeted early Friday morning that he and his wife, Melania, had tested positive for COVID-19 shortly after confirming Hope Hicks, a close aide to him, had contracted the virus.

Trump, 74, has a mild fever, according to a source familiar with the matter. In a memo, Conley said Trump "remains fatigued but in good spirits" as of Friday afternoon.

Conley said earlier that Trump was also undergoing experimental antibody cocktail treatment.

"As a precautionary measure, he received a single 8 gram dose of Regeneron's polyclonal antibody cocktail. He completed the infusion without incident," Conley wrote. "In addition to the polyclonal antibodies, the President has been taking zinc, vitamin D, famotidine, melatonin and a daily aspirin."

READ MORE: Trump, wife test positive for COVID-19

Antibodies are proteins made by the body’s immune system that latch onto and neutralize an invading virus. Regeneron’s cocktail - which contains an antibody made by the company and a second isolated from humans who recovered from COVID-19 - is designed so that its two antibodies bind to the coronavirus’ spike protein, limiting the ability of viruses to escape.

US President Donald Trump arrives at Walter Reed National Military Medical Center, in Bethesda, Maryland, Oct 2, 2020, on Marine One helicopter after he tested positive for COVID-19. (JACQUELYN MARTINE / AP)

White House communications aide Alyssa Farah told CNN that Trump has not transferred his power temporarily to Vice President Mike Pence under the 25th amendment of the US Constitution.

As a precautionary measure he received a single 8 gram dose of Regeneron's polyclonal antibody cocktail. He completed the infusion without incident.

 Sean Conley, White House physician

"The president is in charge," she said.

Doctor Conley added the first lady "remains well with only a mild cough and headache" and that the remainder of the first family are well and tested negative for COVID-19 on Friday.

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Pence has taken COVID-19 tests and the results were negative.

Democratic presidential nominee and former US Vice President Joe Biden also tested negative for the virus.

"This cannot be a partisan moment," Biden tweeted on Friday afternoon. "We have to come together as a nation." 

Trump’s campaign manager, Bill Stepien, also tested positive for COVID-19 on Friday, becoming the latest associate of the president to become infected with the disease, spokesman Tim Murtaugh said late Friday.

White House chief of staff Mark Meadows said he expects more people in the White House to test positive for COVID-19.

Hicks traveled with Trump multiple times this week, including aboard Marine One, the presidential helicopter, for a rally in Minnesota on Wednesday, and aboard Air Force One to the Cleveland debate.

In addition to the Trumps and Hicks, multiple White House officials, including the president's national security advisor Robert O'Brien and Pence's communications director Katie Miller, as well as other staffers, have previously tested positive for the virus.