Melatonin produced in the lungs acts as a barrier defense against SARS-CoV-2, the virus that causes COVID-19, by blocking the expression of genes that encode proteins in cells acting as viral entry points. Pre-clinical and clinical trials will be needed to prove the therapeutic efficacy of melatonin against the virus, the researchers stress in an article on the study published in the journal Melatonin Research. https://neurosciencenews.com/melatonin-lungs-covid-17632/