This study aims to evaluate the oral administration of Bromhexine hydrochloride for the prevention of SARS-CoV-2 infection and COVID-19 disease in medical personnel assisting patients with a new coronavirus disease. The aim of the study is to determine the preventive role of this drug in the framework of reducing the incidence of coronavirus infection in risk groups (medical personnel). Several studies show, that the acute respiratory syndrome coronavirus SARS-CoV uses endosomal cysteine proteases cathepsin B and L (CatB/L) and the transmembrane protease serine type 2 (TMPRSS2) for the priming of the viral S-protein. The new coronavirus SARS-CoV-2 penetrates into alveolar epithelial type two cells through a similar mechanism. In detail, viral S-protein binds to pneumocyte angiotensin-converting enzyme 2 (ACE2) and then undergoes cleaving by TMPRSS2 in S1- and S2-subunits. This leads to the release of a fusion peptide, which allows the virus to enter the cell via endocytosis. Therefore, the protease TMPRSS2 can serve as a target for pharmacological agents to prevent the penetration of the SARS-CoV-2 into the cell. Bromhexine blocks the TMPRSS2 ability to activate a zymogen precursor of tissue plasminogen activator in vitro. Interestingly, TMPRSS2 is blocked by much lower concentrations then required to inactivate other proteases in the cell culture. However, these data cannot be simply extended to the clinical practice: whether the concentration of bromhexine in the lung tissue of properly treated patients would be enough to prevent the virus entry through the TMPRSS2-inactivation remains unclear. A randomized study in people at risk for coronavirus infection will clarify the role of Bromhexine hydrochloride as a prevention of this disease.
