Protein C

Class

Recombinant modified thrombin variant ("E-WE thrombin"), a selective protein C activator

Pathway

Protein C anticoagulant pathway -- generates activated protein C to interrupt thrombus formation without systemic anticoagulant effect

Protein C is a vitamin K-dependent protein that circulates in blood as an inactive precursor. It becomes activated protein C (APC) when thrombin, the central clotting enzyme, binds a partner receptor called thrombomodulin on the surface of blood vessel lining cells. APC then degrades two clotting factors, Va and VIIIa, slowing further thrombin generation — the body's natural brake on runaway coagulation. Because thrombin itself performs this activation step, using native thrombin as a drug would also drive clot formation directly, defeating the purpose. Engineered thrombin variants have been designed to lose the clot-promoting activities of thrombin while preserving, or enhancing, its ability to activate protein C when bound to thrombomodulin. Such an agent aims to interrupt pathological thrombus formation and support the protective, anti-inflammatory, and blood-vessel-stabilizing effects of APC, without the broad bleeding liability of conventional anticoagulants that suppress coagulation indiscriminately. This mechanism is relevant to conditions involving excessive or misdirected clotting and to vascular injury syndromes where loss of the protein C pathway's protective signaling contributes to organ damage, offering a route to rebalance coagulation rather than blocking it wholesale.