TMPRSS2 as a potential target for treatments of COVID-19 and respiratory infectious viruses in lung

Project Summary In December of 2019, a novel coronavirus, now referred to as severe acute respiratory syndrome coronavirus 2 (SARS- CoV-2), struck Wuhan, China and unleashed the current coronavirus disease (COVID-19) pandemic. There are currently no medications or vaccines proven to be effective for the treatment or prevention of COVID-19. There is an urgent need to identify effective therapeutic options: a vaccine and/or drugs that can effectively cure the disease. Although a vaccine will be the ultimate way to combat the virus as a community, antivirals are likely to be developed and approved faster, especially since a broadly available and effective vaccine is likely years away. Antivirals would hugely benefit the population that is currently affected by the virus, helping individuals recover and reducing the number of deaths. Antivirals would also reduce the number of positive carriers and thus curb the spread of the disease. This proposal aims to develop an efficient antiviral to impede the virus' entry into cells, specifically into lung alveolar type II (AT2) cells, the stem cells of the distal lung. Thanks to recent studies, we know which "door" (a receptor called ACE2) and "key" (a protease called TMPRSS2) the virus uses to enter cells. Our goal is to remove the "key" so the virus cannot open the "door" and enter host cells. We will use a recently developed 3-dimensional (3D) in vitro lung organoid model that recapitulates many aspects of lung structure and the cellular environment and that has been used to study respiratory viruses, including SARS-CoV-2. This system represents tissues better than cell lines, but offers the benefit of being less complex than tissue explants or animal models. In addition, we have generated a panel of highly sensitive and specific mouse monoclonal antibodies (mAbs) directed against TMPRSS2. In preliminary studies, the lead TMPRSS2 mAb, AL20, shows no signs of cytotoxicity with a trend towards inhibition of SARS-CoV-2 pseudovirus entry in cell lines. Furthermore, we have identified at least two serine protease inhibitors (serpins) that form complexes with TMPRSS2, and the presence of these complexes is inversely correlated with the SARS-CoV-2 infection rate. These findings lead to our hypothesis that targeting TMPRSS2 can inhibit SARS-CoV-2 viral entry and spread. To test our hypothesis, we will first test the efficacy of AL20 for blocking the entry of SARS-CoV-2 into AT2 cells in lung organoids, and elucidate the underlying mechanisms. We will then evaluate the effects of serpins on TMPRSS2 activity and SARS-CoV-2 viral entry and spread. Finally, to explore the feasibility of advancing AL20 to human trials, we also propose to humanize and test AL20 in available K18-hACE2 mice. This transgenic strain expresses human ACE2, regulated by the KRT18 promoter that directs expression to lung epithelia, to provide the pre-clinical data necessary to test the feasibility of advancing to human clinical trials. These studies will provide critical insights into the mechanisms whereby TMPRSS2 regulates SARS-CoV-2 entry, and suggest potential therapeutic candidates against COVID-19. The proposed work has the potential to impact the lives of millions of individuals affected by COVID-19 and other respiratory viruses, such as influenza A, that use TMPRSS2 to enter cells.