Dr. Marc Siegel says a new experimental pill developed to treat COVID-19 could be the "holy grail of therapeutics" used against the virus. First-stage testing of Molnupiravir, developed by Merck and Ridgeback Biotherapeutics, showed promising signs of effectiveness in reducing the virus in patients.

COVID-19 PILL EFFECTIVE IN PRELIMINARY TESTING MAY BE 'HOLY GRAIL' OF PANDEMIC, DR. MARC SIEGEL SAYS

"It’s actually something that you can take on the first day," Siegel said on "America’s Newsroom" on Monday.

"In trials, phase two trials, it’s showing that it gets rid of the virus completely, to where you can’t see any evidence of the virus," he added. "So it cuts down dramatically on the severity of cases."

The Fox News medical contributor told Dana Perino the drug still needs to be tested on larger groups of people.

"What’s left is to try it in thousands and thousands of people," Siegel said. "And if that goes through and that works, then we’re going to have something we really, really need."

"What’s really important is that it’s safe so far … Of all of the drugs we’ve been testing, it’s the first one we’re seeing that may really work very, very early," he said. Siegel added that the drug could be helpful "for people that get [coronavirus] even despite being vaccinated, or people who haven’t yet been vaccinated, or people who can’t be vaccinated."

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The medication would function as an at-home, five-day treatment, similar to Tamiflu, to stop the virus from reproducing before causing major damage. It would require a prescription from a doctor, Siegel said.

"A lot of patients that I think have flu, I give them Tamiflu," he said. "If I had patients that I thought had COVID, I would give them this."

Fox News’ Angelica Stabile contributed to this report.