The human gene SERPINC1 produces antithrombin III, the most important serine protease inhibitor in plasma that regulates the blood coagulation cascade (van Boven & Lane 1997). Antithrombin III binds to membrane-associated low molecular weight heparins (LMWHs) and their derivatives (SERPINC1 activators) on the surface of normal endothelial cells. This binding increases the affinity of antithrombin III for thrombin approximately 1000-fold, inactivating thrombin and other proteases involved in blood clotting (e.g. factor Xa) and resulting in an overall decrease in clotting ability (Holmer et al. 1986, Eriksson et al. 1995, Mushunje et al. 2003).

The Covid-19 pandemic is an infection caused by the SARS-CoV-2 coronavirus. Severe cases of this infection can lead to acute respiratory distress syndrome and coagulation changes leading to a higher risk of thrombosis, especially pulmonary embolism (Susen et al. 2020). LMWHs may play a role as potential attachment factors for SARS-CoV-2 (Tandon et al. 2020), potentially reducing the incidence and/or severity of thrombosis (Marietta et al. 2020).