Long-lasting Chlorine Dioxide (ClO2) Aqueous Solution Presented by Taiko Pharmaceutical and Kitasato University Inactivates over 99.99% of SARS-CoV-2 (COVID-19 Virus)

- Solution Also Effective against Alpha and Gamma Variants of SARS-CoV-2 -

Taiko Pharmaceutical Co., Ltd. based in Osaka, Japan, hereby announced that long-lasting chlorine dioxide (ClO2) aqueous solution (*1) inactivated over 99.99% of SARS-CoV-2 (COVID-19 Virus), including its Alpha and Gamma variants (*2), in a test conducted in collaboration with Kitasato Institute/Kitasato University in Tokyo, Japan.

SARS-CoV-2 strains were mixed with Taiko Pharmaceutical’s long-lasting ClO2 aqueous solution (*1) at the ratio of 1:19 (154 ppm (*3) in aqueous solution remained active for three years’ storage) and the infectivity titer was determined by the plaque assay (*5) at 10 sec and 60 sec using TMPRSS2-expressing Vero E6 cells (*4). The results revealed that the ClO2 aqueous solution inactivated over 99.99% of SARS-CoV-2, including the two variant strains.

The Alpha and Gamma variants of SARS-CoV-2 contain N501Y (*6) and E484K (*6) mutation, respectively, and these were suggested to affect, respectively, the infection/transmission potency, and antigenic drift. Currently, worldwide dissemination of the N501Y variant (*7, 8) has been confirmed.

A study reported that ClO2 denatures the spike protein on the surface of SARS-CoV-2 and inhibits its binding to the human ACE2 receptor (*9). The current study adds invaluable information for the effectiveness of long-lasting ClO2 aqueous solution in disinfecting the coronaviruses.

The pandemic dissemination of the novel coronavirus infectious disease (COVID-19) has seriously damaged the human society, threatening millions of human lives. Strategies to combat COVID-19 may be to develop vaccines to establish the herd immunity, effective drugs and disinfectants to inactivate the viruses.

Table 1: Number of Viral Particles on Day 3 of Culture

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Fig. 1: Plaque Assay

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Notes:

(*1) Used Taiko Pharmaceutical’s patented long-lasting ClO2 aqueous solution (Patent No. 5757975, 3 years after production). "Cleverin Spray" commonly marketed in Japan was used in this experiment.

(*2) Subject microorganisms: SARS-CoV-2 (3 strains above) provided by the National Institute of Infectious Diseases. hCoV-19/Japan/TY-WK-521 (conventional strain), hCoV-19/Japan/QHN001/2021 (Alpha variant), hCoV-19/Japan/TY7-501/2021 (Gamma variant).

(*3) Unit of ppm: ppm (parts per million) represents the ratio of 1 part per million. The weight ratio (mg / L = ppm, 1 L water is approximately equal to 1 kg) is used for liquids, and the volume ratio is used for gas. The ppm of this test applies the weight ratio in aqueous solution.

(*4) Subject cells: TMPRSS2-expressing VeroE6 cells: A cell line that is able to proliferate and isolate the SARS-CoV-2 developed by the National Institute of Infectious Diseases. In this study, the one purchased from the JCRB Cell Bank, the National Institutes of Biomedical Innovation, Health and Nutrition, was used.

(*5) Plaque Assay: One of the standard methods for measuring virus infectivity titer in a test sample, which is determined by the number of changes in the shape (plaque or white spot) of virus-infected cells.

(*6) N501Y variant: 501st amino acid of S protein is replaced from aspartic acid (N) to tyrosine (Y). It is suggested to be more infectious than conventional strains. E484K variant: 484th amino acid of S protein is replaced from glutamic acid (E) to lysine (K). Compared to the conventional strains, this variant may work as a stronger suppressor of the immune system and vaccination efficiency.

(*7) National Institute of Infectious Diseases New variant of SARS-CoV-2 suggested to have more infection/transmission capability and changes in antigenicity (8th report). https://www.niid.go.jp/niid/ja/diseases/ka/corona-virus/2019-ncov/2484-idsc/10280-covid19-41.html

(*8) Ministry of Health, Labour and Welfare (the measures against COVID-19 (with SARS-CoV-2 of variant strains)) https://www.mhlw.go.jp/content/10900000/000776469.pdf

(*9) Inhibition of the Binding of Spike Protein of SARS-CoV-2 Coronavirus to Human Angiotensin-Converting Enzyme 2 by Chloride Dioxide, Annals of Pharmacology and Pharmaceutics, Volume 5, Issue 5, Article1195 (2020)