Malaria Drug Chloroquine Does Not Inhibit COVID-19 Infection in Human Lung Cells

SARS-CoV-2 Illustration

Existing drugs used for treating other diseases are being repurposed for the treatment of COVID-19. Chloroquine is a drug that is used to treat malaria. The study shows that chloroquine does not prevent SARS-CoV-2 entry into human lung cells and subsequent spread of the virus in these cells.

More than 600,000 people worldwide have fallen victim to the lung disease COVID-19 so far, which is caused by the SARS coronavirus-2 (SARS-CoV-2). In order to obtain an effective therapy for COVID-19 as quickly as possible, drugs that are being used to treat other diseases are currently being repurposed for COVID-19 treatment.

The Infection Biology Unit of the German Primate Center (DPZ) – Leibniz Institute for Primate Research in Göttingen, together with colleagues at the Charité in Berlin, was able to show that the malaria drug chloroquine, which has been demonstrated to inhibit the SARS-CoV-2 infection of African green monkey kidney cells, is not able to prevent infection of human lung cells with the novel coronavirus. Chloroquine is therefore unlikely to prevent the spread of the virus in the lung and should not be used for the treatment of COVID-19.

It is known that SARS-CoV-2 is able to use two different routes to enter cells. First, after attaching to the cells, the virus can fuse directly with the plasma membrane and introduce its genetic material into the host cell. Second, it can enter the interior of the cells upon uptake via transport structures, called endosomes. In both cases, the attachment of the virus to the cells and subsequent entry is mediated by the viral spike protein. For this purpose, the spike protein must be activated either by the enzyme cathepsin L (in endosomes) or by the enzyme TMPRSS2 (on the cell surface). Depending on the cell type, both enzymes or only one of them can be available for activation.

Dr Markus Hoffmann

Dr. Markus Hoffmann examines a cell culture under the microscope. Credit: Nadine Krüger

Chloroquine is a drug that is used to treat malaria. Since chloroquine inhibits the infection of monkey kidney cells with SARS-CoV-2, chloroquine has been tested in clinical trials as a possible candidate for the treatment of COVID-19. However, how chloroquine inhibits the infection of monkey kidney cells was not clear. The current study shows that chloroquine inhibits viral entry into these cells, most likely by blocking cathepsin L activity. This raised the question of whether chloroquine also inhibits the infection of lung cells that are known to produce TMPRSS2 but only a small amount of cathepsin L.

The study shows that chloroquine does not prevent SARS-CoV-2 entry into human lung cells and subsequent spread of the virus in these cells. “In this study, we show that the antiviral activity of chloroquine is cell type-specific and that chloroquine does not block the infection of lung cells. This means that in future tests of potential COVID-19 drugs, care should be taken that relevant cell lines are used for the investigations in order not to waste unnecessary time and resources in our search for effective COVID-19 therapeutics,” says Stefan Pöhlmann, head of the Infection Biology Unit at DPZ, adding: “COVID-19 is primarily caused by the infection of lung cells, for this reason these cells should be given priority in efficacy tests.”

Reference: “Chloroquine does not inhibit infection of human lung cells with SARS-CoV-2” by Markus Hoffmann, Kirstin Mösbauer, Heike Hofmann-Winkler, Artur Kaul, Hannah Kleine-Weber, Nadine Krüger, Nils C. Gassen, Marcel A. Müller, Christian Drosten and Stefan Pöhlmann, 22 July 2020, Nature.
DOI: 10.1038/s41586-020-2575-3

The study was conducted in cooperation with the Charité in Berlin and the University of Bonn.

11 Comments on "Malaria Drug Chloroquine Does Not Inhibit COVID-19 Infection in Human Lung Cells"

  1. Well, one more study that shows that Chloroquine alone does not help very much with C19.

    The study has no mentioning of “zinc” to be found in their paper.

    Media should always mention that it makes a difference if Chloroquine is used solitarily or in combination with zinc.

  2. Did the tests also include the use of zinc?
    I recall several of the doctors who claimed that treating the patients with
    the malaria drug combined with zinc had worked.

  3. Theodore Frimet | July 25, 2020 at 6:03 am | Reply

    Zinc has always had the potential of enhancing antiviral immunity. However, you are missing the point. Chloroquine is effective on MONKEY KIDNEY CELLS, and not human lung tissue.

    Given the short time period for all experimenters, and the simple, and most “in-your’face” fact that resources will always be limited, stop the nonsense, and devote time and energy to what is promising, and not hunker down behind a wall of theoretical toilet paper.

    Zinc plays a role. Where there is a deficiency there will be inflammation as a result. It is not rocket science to understand that a person that suffers obesity, and inflammation, cannot induce a response to clear this virus from their lung tissue – and the co-morbid result of this inflammation is that OUR immune system’s T-Cells are activated to destroy the lining of our lungs.

    So, it isn’t SARS-CoV-2 per se that is killing you. It is you, that is killing you. No amount of chloroquine in combination with Zinc is going to be more promising than wishing that the tooth fairy was real.

    Loose weight. Eat healthy. Moderate exercise, and for the sake of your fellow Americans, wear a mask.

  4. Why don’t you just go with the chlorine dioxide water solution? It’s inexpensive, available and will work without planned side effects. Everything or anything else will be a crime against humanity.

  5. No mention of sample size
    No mention whose cells, how taken, etc.
    And no mention of zinc levels in blood or tissue of participants
    This is not science
    10 cells in one Petri dish and 10 cells in another dish

    This does not seem to be the rigorous research the German Institutes are known for!

  6. Chris Chaudoir | July 25, 2020 at 11:20 pm | Reply

    Chloroquine and hydroxychloroquine are zinc ionophores that allow zinc ions to pass into the cells, where zinc disrupts viral replication. The effectiveness of chloroquine has never been dependent upon blocking cell entry of SARS-CoV-2.

  7. Chloroquine also helped managing the cytokine storm and the extreme response of the immune system. Which was one of the main causes of death.

  8. Clyde Spencer | July 27, 2020 at 1:32 pm | Reply

    One should entertain the possibility that zinc alone may be the active ingredient in the HCQ ‘cocktail.’ If HCQ is acting as an ionophore, then it would be reasonable that the usual dietary zinc, and zinc commonly found in supplementary vitamins, would be more effective in suppressing the virus in combination with HCQ. However, this study found no such improvement! In a “controlled experiment” one minimizes the potential variables and only changes one variable at a time.

    As far as I know, no one has attempted experiments with variable concentrations of zinc alone. Although, it is commonly held that zinc gluconate is effective against colds. No HCQ apparently needed.

    There have been so many drugs found that are apparently useful, one should also entertain the hypothesis that the results seen with HCQ are either random variation arising from natural partial immunity, or a simple placebo effect.

  9. AbleArcher1983 | July 27, 2020 at 6:29 pm | Reply

    Yes it does @sshole, cut the politics and stop trying to deprive people of a proven treatment

  10. dont say thet

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