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A drug developed over half a century ago to treat malaria is showing signs that it may also help cure COVID-19 — especially when combined with an antibiotic, a promising new study reveals.

Hydroxychloroquine, sold under the brand name Plaquenil — and also used to treat arthritis and other ailments — was determined to be effective in killing the deadly bug in laboratory experiments, Forbes reported, citing findings published March 9 in the Clinical Infectious Diseases journal.

“(W)e predict that the drug has a good potential to combat the disease,” the study’s authors, most from the Chinese Academy of Sciences in Wuhan, wrote in a letter published in Cell Discovery on Wednesday, according to the report.

Now, French physician-researchers have completed a largely successful clinical trial using the drug — approved for use in the US in 1955 — to treat confirmed COVID-19 patients, according to a study published Wednesday.

A total of 36 patients — including 20 treated individuals and 16 infected controls — were enrolled in the study, led by Didier Raoult, an infectious disease expert from l’Institut Hospitalo-Universitaire in Marseille.

The treated group was given 600 mg of Plaquenil each day.

The researchers found that 50 percent of the treated group turned from positive to negative for the virus by the third day — and by day six, that figure was up to 70 percent.

Of the 20 test patients, six who were treated with both Plaquenil and the antibiotic azithromycin showed impressive results — with five testing negative at day three. All six of them tested negative at day six.

“Despite its small sample size our survey shows that hydroxychloroquine treatment is significantly associated with viral load reduction/disappearance in COVID-19 patients and its effect is reinforced by azithromycin,” the study concluded.

Meanwhile, researchers found that a pill containing two HIV drugs touted as a potential treatment for COVID-19 was not effective.

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A test of Chinese patients with a severe case of the novel coronavirus found that the 99 who received AbbVie Inc.’s Kaletra, a cocktail of lopinavir and ritonavir, did not do any better than the 100 who received standard care.

With Post wires