A drug used to treat malaria and arthritis has shown promise against coronavirus and could be “a game changer” in stopping the outbreak, President Donald Trump announced at a White House press conference Thursday.

The already existing drug, known as Hydroxychloroquine, exhibited “encouraging early results against the virus. We’re going to be able to make that drug available immediately” by prescription, the president said.

Trump said the drug was being “fast-tracked” by the FDA, but the agency later clarified that the drug had not yet been approved to treat COVID-19, according to Bloomberg News.

“Nice part is it’s been around a long time, so if things don’t go well, we know it won’t kill anyone,” Trump said.

After the press conference, experts quickly disagreed with the president about the effectiveness of the drug, and said the public should temper any optimism about it being a true vaccine.

Thus far, no U.S. clinical trials have been conducted to show its effectiveness against the virus, according to reports, although French physician-researchers have already completed their own largely successful clinical trial using the drug, according to The New York Post.

Scientists are working around the clock to identify treatments against the disease. Some of them have touted Hydroxychloroquine — a common derivative of chloroquine — which is sold under the brand name Plaquenil, according to Newsweek.

An Emory doctor disputed the president’s claim that the drug was readily available.

The New York Post reports the drug was effective in killing the novel coronavirus in laboratory experiments, citing findings published March 9 in the Clinical Infectious Diseases journal.

In the study, the scientists saw a “significant” reduction of the virus in patients treated with the drug, and 70 percent of them were considered cured after six days of treatment, Newsweek reports.

Trump spoke for more than an hour alongside Vice President Mike Pence, White House coronavirus response coordinator Dr. Deborah Birx, and other members of the national coronavirus task force.

Pence said virus testing was now available in all 50 states, and that tens of thousands of ventilators were on the way to treat patients. He added that the tests will only be given to those who exhibit symptoms.

During his remarks, Trump said Carnival Cruises has offered to provide ships to help with treatment for the COVID-19, according to NPR.

Trump also said he supports investing government money in companies that are struggling under the weight of the outbreak.

Previously

A day earlier, Trump invoked rarely used emergency powers to marshal critical medical supplies against the pandemic. Trump also signed an aid package — which the Senate approved earlier Wednesday — that will guarantee sick leave to workers who fall ill.

Trump tapped his authority under the 70-year-old Defense Production Act to give the government more power to steer production by private companies and try to overcome shortages in masks, ventilators and other supplies.

Trump has taken other extraordinary steps to steady the nation.

The Canada-U.S. border, the world's longest, was effectively closed, save for commerce and essential travel, while the administration pushed its plan to send relief checks to millions of Americans.

Trump said he will expand the nation's diagnostic testing capacity and deploy a Navy hospital ship to New York City, which is rapidly becoming an epicenter of the pandemic, and another such ship to the West Coast. And the Housing and Urban Development Department will suspend foreclosures and evictions through April to help the growing number of Americans who face losing jobs and missing rent and mortgage payments.

— Information provided by the Associated Press was used to supplement this report. This is a developing story. Please return to AJC.com for updates.