The Lancet, one of the world's top medical journals, on Thursday retracted an influential study that raised alarms about the safety of the experimental Covid-19 treatments chloroquine and hydroxychloroquine amid scrutiny of the data underlying the paper.
The retraction came at the request of the authors of the study, published last month, who were not directly involved with the data collection and sources, the journal said.
"We can no longer vouch for the veracity of the primary data sources," Mandeep Mehra of Brigham and Women's Hospital, Frank Ruschitzka of University Hospital Zurich, and Amit Patel of University of Utah said in a statement. "Due to this unfortunate development, the authors request that the paper be retracted."
The retraction is sure to add fuel to contentious arguments about the potential of chloroquine and hydroxychloroquine, two old malaria drugs, in Covid-19, the disease caused by the novel coronavirus. President Trump has touted them as valuable treatments, despite a lack of rigorous data showing they have a benefit.
Meanwhile, on Wednesday, researchers reported the results of the first gold-standard clinical trial of hydroxycholoroquine in Covid-19, concluding that it did not prevent infections any better than placebo. Other clinical trials, including some looking at the drugs as treatments, are ongoing.
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The Lancet study gained so much attention because it went further than other observational studies that had similarly found the drugs were not associated with improved outcomes for patients. The study, which was purportedly based on patient data from 671 hospitals on six continents, reported the drugs also corresponded to higher mortality.
The findings led to the pause of some global clinical trials studying hydroxychloroquine so researchers could check for any safety concerns. Outside experts, however, quickly raised concerns after noticing inconsistencies in the data. They asked the company that compiled and analyzed the data, known as Surgisphere, to explain how it sourced its data.
As scrutiny grew, the authors on the paper not affiliated with Surgisphere called for an independent audit. In their statement Thursday, they said that Surgisphere was not cooperating with the independent reviewers and would not provide the data.
"As such, our reviewers were not able to conduct an independent and private peer review and therefore notified us of their withdrawal from the peer-review process," the researchers wrote.
Outside experts have raised similar concerns about another study, published in the New England Journal of Medicine, from many of the same researchers based on Surgisphere data that looked at the safety of blood pressure medications in patients with Covid-19. Earlier this week, the New England Journal issued an "expression of concern" about the paper, and an independent review of that has also been launched.
Concerns about the health risks of chloroquine and hydroxychloroquine were based on evidence beyond the Lancet paper. Earlier, the Food and Drug Administration warned the drugs should not be used in Covid-19 outside a clinical trial or beyond hospitalized patients because of the risks to heart health.
The drugs are safe for people to take for malaria, rheumatoid arthritis, and lupus, for whom they are shown to have benefits, experts stress.