A noted medical expert threw cold water on the idea that the anti-malarial medication hydroxychloroquine is a game-changing coronavirus treatment on Monday, delivering a stark fact-check on Fox News, which has repeatedly pushed the theory along with President Donald Trump.

Fox News host Dana Perino asked biologist Dr. William Haseltine, who is president of ACCESS Health International and a former Harvard Medical School professor, to weigh in on the drug’s potential use as a treatment for COVID-19, the respiratory disease caused by the new coronavirus.

“It’s sad, to me, that people are promoting that drug. We know already, from studies, at best it will have a very mild effect — at very best,” said Haseltine, who is well known for his groundbreaking research into cancer, genomics and HIV/AIDS.

The scientist noted that a number of studies conducted on the drug’s effects against coronavirus have yielded conflicting results and that its use against other viruses in the past has been ineffective. He also highlighted the life-threatening impact it could have on people taking other medications.

“It is not something to take unless a doctor prescribes it,” he said.

A day earlier, the president had reasoned that there was nothing to lose by trying the unapproved drug as a treatment, prompting multiple medical professionals to speak up about the many dangers of taking hydroxychloroquine when it’s not yet proven to work in this setting.

Perino then brought up exaggerated claims about the drug’s efficacy that have been pushed by her Fox News colleagues.

“I know you don’t go by anecdotal evidence, but there are stories of people saying that they’ve had this Lazarus effect by using this drug,” she said.

Haseltine labeled the stories “complete and utter nonsense.”

“In any situation, there are always going to be people who promote one kind of quack cure or another. And there are Lazarus effects. In every epidemic I’ve ever looked at, it’s always the case. Let me just repeat, we know that at very best, this drug will have a very mild effect on changing the course of the disease, if it has any effect at all,” he said.

“That is what the data has shown so far, and I am convinced that that’s what further studies will show. And it’s not without adverse consequence. It is irresponsible to promote this drug at this time.”

Fox News hosts including Laura Ingraham and Sean Hannity, as well as their guests, have touted the drug time and time again, despite persistent advice from medical experts about the dangers of endorsing an unapproved treatment. 

Last month, Ingraham tweeted praise for hydroxychloroquine, claiming that it was showing “very promising results” in a New York hospital and suggesting that one patient made a Lazarus-like recovery. The tweet was later removed from the platform. Hannity, too, hyped the drug on multiple occasions, going as far as to say on his radio show he would be “all over” the drug if he was diagnosed with coronavirus.

Aside from risks posed by taking a medication not yet approved for the treatment of coronavirus or shown to be effective against it, stockpiling the drug can severely endanger those who do depend on it for approved treatment.

Hydroxychloroquine is currently FDA-approved only for conditions including rheumatoid arthritis, lupus and as an anti-malarial agent. Its known side effects range from nausea and hallucinations to potentially fatal cardiac arrhythmias.