Antiviral activity of chloroquine against coronaviruses discovered at KU Leuven in 2004

Chloroquine, an antimalarial medicine that has been on the international market since 1934, proves to be active against the novel SARS coronavirus type 2 (COVID-19). The antiviral activity of chloroquine was already discovered in 2004 by a team of virologists at KU Leuven.


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Experts from the Chinese Ministry of Science and Technology confirmed at a press conference on 17 February that chloroquine has a curative effect in clinical trials on patients with COVID-19. The trials were conducted in patients in 10 hospitals in Beijing, Hunan, and Guangdong. Patients who received chloroquine during a week had less fever, regained lung function performance quicker, and were faster to clear the virus from their bodies.

The antiviral effects of chloroquine against SARS coronaviruses were already discovered in 2004 by a team of virologists headed by Professor Marc Van Ranst at KU Leuven. In their biosafety-level-3 (BSL-3) laboratory at the Rega Institute, they tested the activity of chloroquine against the SARS coronavirus type 1 in cell cultures. Chloroquine was shown to have an antiviral effect at concentrations that could safely be used in humans. By August 2004, the outbreak of SARS had abated in China and Canada, so that chloroquine could no longer be tested against SARS coronaviruses in patients.

Professor Marc Van Ranst: “KU Leuven was not involved in the clinical trials in China in which the effects of chloroquine against the novel SARS coronavirus type 2 virus were tested. However, the tests appear to have been successful, and we are happy to hear that. Chloroquine is cheap and relatively easy to produce in larger quantities, although the number of manufacturers is currently limited. If the results of the clinical trials in China are confirmed by further research, chloroquine may a worldwide impact on the treatment of patients that are infected with this novel coronavirus.”

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