Fig. 3.  Summary of potential therapeutic effects of heparin in coronavirus disease 2019 (COVID-19). 1) Heparin’s classic function as an anticoagulant, through its interaction with antithrombin-III (AT3), may prove beneficial because of the high prevalence of coagulopathy and clinically significant thrombosis in the disease. 2) Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) entry into both endothelial and epithelial cells is believed to be dependent on its interaction with cell surface heparan sulfate; thus, heparin (or carefully designed synthetic heparin-like drugs) may inhibit this interaction and block viral entry. 3) Last, heparin has known anti-inflammatory effects that may confer benefit in COVID-19. This illustration was created with BioRender (https://biorender.com/). ACE2, angiotensin-converting enzyme 2; APC, activated protein C; HS, heparan sulfate; IL, interleukin; PAI-1, plasminogen activator inhibitor 1; TF, tissue factor; TFPI, tissue factor pathway inhibitor; TNF, tumor necrosis factor; tPA, tissue plasminogen activator; uPA, urokinase plasminogen activator, VII, factor VII.