Chloroquine does not inhibit infection of human lung cells with SARS-CoV-2

Hoffmann et al., Nature, (2020), doi:10.1038/s41586-020-2575-3

Jul 2020

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The title of this paper does not appear to match the results. Fig. 1b @100uM shows CQ results in a ~4.5 fold decrease (on a linear scale) in extracellular virus, p=0.05, after 24 hours (we do not see the supplementary data at this time so this is estimated from the graph). This decrease may continue if examined over longer time periods. Fig. 1a shows a ~45-50% entry inhibition @100uM for HCQ/CQ (p=0.0005/0.0045), ~10-30% @10uM (p=0.13/0.99). Inhibition is significantly better with Vero cells. Note that the safe concentration in practice for different cells is not well known, Keyaerts et al. find CC₅₀ of 261uM Keyaerts.

In vitro study of CQ and HCQ inhibition of SARS-CoV-2 into Vero (kidney), Vero-TMPRSS2, and Calu-3 (derived from human lung carcinoma) cells.

Authors reportedly used sodium pyruvate which may inhibit CQ from entering cells twitter.com.

Although there are several theories on how HCQ may help with COVID-19, authors do not consider the most common theory where HCQ functions as a zinc ionophore, facilitating significant intracellular concentrations of zinc. Zinc is known to inhibit SARS-CoV RNA-dependent RNA polymerase activity, and is widely thought to be important for effectiveness with SARS-CoV-2 infezmed.it.

Calu-3 is one of many cell lines derived from human lung carcinomas journals.physiology.org. Calu-3 cells resemble serous gland cells. They do not express 15-lipoxygenase, an enzyme specifically localized to the surface epithelium, but they do express secretory component, secretory leukocyte protease inhibitor, lysozyme, and lactoferrin, all markers of serous gland cells. journals.physiology.org note that the absence of systemic inflammation, circulatory factors, and other paracrine systemic influences is a potential limitation of the isolated cell system.

RT-PCR is used, we note that nucleic acid may persist even after the virus is no longer viable fda.gov.

It is unclear how the authors conclude "CQ does not block SARS-CoV-2 infection of Calu-3" cells, when the results show statistically significant inhibition at higher concentrations.

Further, it is unclear how the authors go from these results in one specific type of pulmonary adenocarcinoma cells that resemble serous gland cells, in vitro, into the title of the paper which claims no inhibition in lung cells.

Further, it is unclear how another leap is made to "will not be effective against COVID-19" given the multiple theories of HCQ/CQ effectiveness.

27 preclinical studies support the efficacy of HCQ for COVID-19:

6 In Silico studies Baildya, Hussein, Navya, Noureddine, Tarek, Yadav

19 In Vitro studies Alsmadi, Andreani, Clementi, Dang, Delandre, Faísca, Kamga Kapchoup, Liu, Milan Bonotto, Mohd Abd Razak, Ou, Purwati, Shang, Sheaff, Wang, Wang (B), Wen, Yao, Yuan

2 In Vivo animal studies Shu-Han Lin, Wen

Important missing comments or errors? Let us know.

1. Alsmadi et al., The In Vitro, In Vivo, and PBPK Evaluation of a Novel Lung-Targeted Cardiac-Safe Hydroxychloroquine Inhalation Aerogel, AAPS PharmSciTech, doi:10.1208/s12249-023-02627-3.springer.com, doi.org.

2. Andreani et al., In vitro testing of combined hydroxychloroquine and azithromycin on SARS-CoV-2 shows synergistic effect, Microbial Pathogenesis, doi:/10.1016/j.micpath.2020.104228.sciencedirect.com, doi.org.

3. Baildya et al., Inhibitory capacity of Chloroquine against SARS-COV-2 by effective binding with Angiotensin converting enzyme-2 receptor: An insight from molecular docking and MD-simulation studies, Journal of Molecular Structure, doi:10.1016/j.molstruc.2021.129891.sciencedirect.com, doi.org.

4. Clementi et al., Combined Prophylactic and Therapeutic Use Maximizes Hydroxychloroquine Anti-SARS-CoV-2 Effects in vitro, Front. Microbiol., 10 July 2020, doi:10.3389/fmicb.2020.01704.frontiersin.org, doi.org.

5. Dang et al., Structural basis of anti-SARS-CoV-2 activity of hydroxychloroquine: specific binding to NTD/CTD and disruption of LLPS of N protein, bioRxiv, doi:10.1101/2021.03.16.435741.biorxiv.org, doi.org.

6. Delandre et al., Antiviral Activity of Repurposing Ivermectin against a Panel of 30 Clinical SARS-CoV-2 Strains Belonging to 14 Variants, Pharmaceuticals, doi:10.3390/ph15040445.mdpi.com, doi.org.

7. Faísca et al., Enhanced In Vitro Antiviral Activity of Hydroxychloroquine Ionic Liquids against SARS-CoV-2, Pharmaceutics, doi:10.3390/pharmaceutics14040877.mdpi.com, doi.org.

8. fda.gov, www.fda.gov/media/136472/download.www.fda.gov/media/136472/download.

9. Hussein et al., Molecular Docking Identification for the efficacy of Some Zinc Complexes with Chloroquine and Hydroxychloroquine against Main Protease of COVID-19, Journal of Molecular Structure, doi:10.1016/j.molstruc.2021.129979.sciencedirect.com, doi.org.

10. infezmed.it, www.infezmed.it/index.php/article?Anno=2020&numero=2&ArticoloDaVisualizzare=Vol_28_2_2020_192.www.infezmed.it/index.php/article?Anno=2020&numero=2&ArticoloDaVisualizzare=Vol_28_2_2020_192.

11. journals.physiology.org, journals.physiology.org/doi/pdf/10.1152/ajplung.1994.266.5.L493.journals.physiology.org/doi/pdf/10.1152/ajplung.1994.266.5.L493.

12. Kamga Kapchoup et al., In vitro effect of hydroxychloroquine on pluripotent stem cells and their cardiomyocytes derivatives, Frontiers in Pharmacology, doi:10.3389/fphar.2023.1128382.frontiersin.org, doi.org.

13. Keyaerts et al., In vitro inhibition of severe acute respiratory syndrome coronavirus by chloroquine, Biochem. Biophys. Res. Comm., 323:1, 8 October 2004, doi:10.1016/j.bbrc.2004.08.085.sciencedirect.com, doi.org.

14. Liu et al., Hydroxychloroquine, a less toxic derivative of chloroquine, is effective in inhibiting SARS-CoV-2 infection in vitro, Cell Discovery 6, 16 (2020), doi:10.1038/s41421-020-0156-0.nature.com, doi.org.

15. Milan Bonotto et al., Cathepsin inhibitors nitroxoline and its derivatives inhibit SARS-CoV-2 infection, Antiviral Research, doi:10.1016/j.antiviral.2023.105655.sciencedirect.com, doi.org.

16. Mohd Abd Razak et al., In Vitro Anti-SARS-CoV-2 Activities of Curcumin and Selected Phenolic Compounds, Natural Product Communications, doi:10.1177/1934578X231188861.sagepub.com, doi.org.

17. Navya et al., A computational study on hydroxychloroquine binding to target proteins related to SARS-COV-2 infection, Informatics in Medicine Unlocked, doi:10.1016/j.imu.2021.100714.sciencedirect.com, doi.org.

18. Noureddine et al., Quantum chemical studies on molecular structure, AIM, ELF, RDG and antiviral activities of hybrid hydroxychloroquine in the treatment of COVID-19: molecular docking and DFT calculations, Journal of King Saud University - Science, doi:10.1016/j.jksus.2020.101334.sciencedirect.com, doi.org.

19. Ou et al., Hydroxychloroquine-mediated inhibition of SARS-CoV-2 entry is attenuated by TMPRSS2, PLOS Pathogens, doi:10.1371/journal.ppat.1009212.plos.org, doi.org.

20. Purwati et al., An in vitro study of dual drug combinations of anti-viral agents, antibiotics, and/or hydroxychloroquine against the SARS-CoV-2 virus isolated from hospitalized patients in Surabaya, Indonesia, PLOS One, doi:10.1371/journal.pone.0252302.plos.org, doi.org.

21. Shang et al., Inhibitors of endosomal acidification suppress SARS-CoV-2 replication and relieve viral pneumonia in hACE2 transgenic mice, Virology Journal, doi:10.1186/s12985-021-01515-1.biomedcentral.com, doi.org.

22. Sheaff, R., A New Model of SARS-CoV-2 Infection Based on (Hydroxy)Chloroquine Activity, bioRxiv, doi:10.1101/2020.08.02.232892.biorxiv.org, doi.org.

23. Shu-Han Lin et al., Inhalable Chitosan-Based Hydrogel as a Mucosal Adjuvant for Hydroxychloroquine in the Treatment for SARS-CoV-2 Infection in a Hamster Model, Journal of Microbiology, Immunology and Infection, doi:10.1016/j.jmii.2023.08.001.sciencedirect.com, doi.org.

24. Tarek et al., Pharmacokinetic Basis of the Hydroxychloroquine Response in COVID-19: Implications for Therapy and Prevention, European Journal of Drug Metabolism and Pharmacokinetics, doi:10.1007/s13318-020-00640-6.springer.com, doi.org.

25. twitter.com, twitter.com/JaclynHord/status/1302680394244947969.twitter.com/JaclynHord/status/1302680394244947969.

26. Wang et al., Chloroquine and hydroxychloroquine as ACE2 blockers to inhibit viropexis of 2019-nCoV Spike pseudotyped virus, Phytomedicine, doi:10.1016/j.phymed.2020.153333.nih.gov, doi.org.

27. Wang (B) et al., Remdesivir and chloroquine effectively inhibit the recently emerged novel coronavirus (2019-nCoV) in vitro, Cell Res. 30, 269–271, doi:L10.1038/s41422-020-0282-0.nature.com, doi.org.

28. Wen et al., Cholinergic α7 nAChR signaling suppresses SARS-CoV-2 infection and inflammation in lung epithelial cells, Journal of Molecular Cell Biology, doi:10.1093/jmcb/mjad048.oup.com, doi.org.

29. Yadav et al., Repurposing the Combination Drug of Favipiravir, Hydroxychloroquine and Oseltamivir as a Potential Inhibitor Against SARS-CoV-2: A Computational Study, Research Square, doi:10.21203/rs.3.rs-628277/v1.researchsquare.com, doi.org.

30. Yao et al., In Vitro Antiviral Activity and Projection of Optimized Dosing Design of Hydroxychloroquine for the Treatment of Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2), Clin. Infect. Dis., 2020 Mar 9, doi:10.1093/cid/ciaa237.oup.com, doi.org.

31. Yuan et al., Hydroxychloroquine blocks SARS-CoV-2 entry into the endocytic pathway in mammalian cell culture, Communications Biology, doi:10.1038/s42003-022-03841-8.nature.com, doi.org.

Hoffmann et al., 22 Jul 2020, peer-reviewed, 10 authors.

In Vitro studies are an important part of preclinical research, however results may be very different in vivo.

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Chloroquine does not inhibit infection of human lung cells with SARS-CoV-2

Markus Hoffmann, Kirstin Mösbauer, Heike Hofmann-Winkler, Artur Kaul, Hannah Kleine-Weber, Nadine Krüger, Nils C Gassen, Marcel A Müller, Christian Drosten, Stefan Pöhlmann

Nature, doi:10.1038/s41586-020-2575-3

The coronavirus disease 2019 (COVID-19) pandemic, which is caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has been associated with more than 780,000 deaths worldwide (as of 20 August 2020). To develop antiviral interventions quickly, drugs used for the treatment of unrelated diseases are currently being repurposed to treat COVID-19. Chloroquine is an anti-malaria drug that is used for the treatment of COVID-19 as it inhibits the spread of SARS-CoV-2 in the African green monkey kidney-derived cell line Vero 1-3 . Here we show that engineered expression of TMPRSS2, a cellular protease that activates SARS-CoV-2 for entry into lung cells 4 , renders SARS-CoV-2 infection of Vero cells insensitive to chloroquine. Moreover, we report that chloroquine does not block infection with SARS-CoV-2 in the TMPRSS2-expressing human lung cell line Calu-3. These results indicate that chloroquine targets a pathway for viral activation that is not active in lung cells and is unlikely to protect against the spread of SARS-CoV-2 in and between patients. Chloroquine and hydroxychloroquine are used for the treatment of malaria and have been widely used to treat patients with COVID-19. Both of these drugs are currently under investigation in more than 80 registered clinical trials for the treatment of COVID-19 worldwide 2,3 . Chloroquine and hydroxychloroquine inhibit the ability of SARS-CoV-2 to infect Vero cells 1, 5, 6 , providing a rational for using these drugs for the treatment of COVID-19. However, it is unknown whether these drugs inhibit the infection of lung cells and it is poorly understood how they inhibit infection with SARS-CoV-2. Chloroquine and hydroxychloroquine increase the endosomal pH of cells and inhibit viruses that depend on low pH for cell entry 7 . We investigated whether these drugs could also block the cell entry by SARS-CoV-2 and whether entry inhibition accounted for the prevention of infection with SARS-CoV-2. Moreover, we investigated whether entry inhibition is cell-type-dependent, as the virus can use pH-dependent and pH-independent pathways for entry into cells. The spike (S) protein of SARS-CoV-2, which mediates viral entry, is activated by the endosomal-pH-dependent cysteine protease cathepsin L (CTSL) in some cell lines 4 . By contrast, entry into airway epithelial cells, which express low levels of CTSL 8 , depends on the pH-independent, plasma-membrane-resident serine protease TMPRSS2 4 . Notably, the use of CTSL by coronaviruses is restricted to cell lines 8-10 , whereas TMPRSS2 activity is essential for the spread and pathogenesis of the virus in the infected host 11, 12 . We compared the inhibition by chloroquine and hydroxychloroquine of S-mediated entry into Vero (kidney), TMPRSS2-expressing Vero and Calu-3 (lung) cells. Calu-3 cells, as with the airway epithelium, express low amounts of CTSL 8 and SARS-CoV-2 entry into these cells is dependent on TMPRSS2 4 .

Reporting summary Further information on research design is available in the Nature Research Reporting Summary linked to this paper. Author contributions M.H. and S.P. designed the study. M.H., K.M., H.H.-W., A.K., H.K.-W., N.K., N.C.G. and M.A.M. performed research. M.H., M.A.M., C.D. and S.P. analysed the data. C.D. provided essential reagents. M.H. and S.P. wrote the manuscript. All authors revised the manuscript. Competing interests The authors declare no competing interests. Additional information Supplementary information is available for this paper at https://doi.org/10.1038/s41586-020-2575-3. Correspondence and requests for materials should be addressed to M.H. or S.P. Reprints and permissions information is available at http://www.nature.com/reprints. Reporting Summary Nature Research wishes to improve the reproducibility of the work that we publish. This form provides structure for consistency and transparency in reporting. For further information on Nature Research policies, see our Editorial Policies and the Editorial Policy Checklist. Statistics For all statistical analyses, confirm that the following items are present in the figure legend, table legend, main text, or Methods section. n/a Confirmed The exact sample size (n) for each experimental group/condition, given as a discrete number and unit of measurement A statement on whether measurements were taken from distinct samples or whether the same sample was measured repeatedly The statistical test(s)..

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