Researchers have found that catalase, a naturally occurring enzyme, holds potential as a low-cost therapeutic drug to treat COVID-19 symptoms and suppress the replication of coronavirus inside the body.

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Catalase is produced naturally and used by humans, animals and plants. Inside cells, the antioxidant enzyme kick starts the breakdown of hydrogen peroxide, which can be toxic, into water and oxygen. According to the study, published in the journal Advanced Materials, the enzyme is also commonly used worldwide in food production and as a dietary supplement. "There is a lot of focus on vaccines and antiviral drugs, and rightly so," said study senior author Yunfeng Lu from the University of California Los Angeles in the US. "In the meantime, our research suggests this enzyme could offer a very effective therapeutic solution for the treatment of hyper inflammation that occurs due to SARS-CoV-2 virus, as well as hyper inflammation generally," Lu added.

Lu's group developed the drug-delivery technology used in the experiments. Three types of tests were conducted, each addressing a different symptom of COVID-19. First, they demonstrated the enzyme's anti-inflammatory effects and its ability to regulate the production of cytokines, a protein that is produced in white blood cells. Cytokines are an important part of the human immune system, but they can also signal the immune system to attack the body's own cells if too many are made -- a so-called "cytokine storm" that is reported in some patients diagnosed with COVID-19. Second, the team showed that catalase can protect alveolar cells, which line the human lungs, from damage due to oxidation.

Finally, the experiments showed that catalase can repress the replication of SARS-CoV-2 virus in rhesus macaques, a type of monkey, without noticeable toxicity. "This work has far-reaching implications beyond the treatment of COVID-19," the study authors wrote. "Cytokine storm is a lethal condition that can complicate other infections, such as influenza, as well as non-infectious conditions, like autoimmune disease," the team noted.