Fibrinogen (precursor); Fibrin (active clot protein) (Fg (for Fibrinogen); no widely used abbreviation for Fibrin)

Fibrinogen is a large, soluble plasma glycoprotein composed of three pairs of polypeptide chains (Aα, Bβ, γ), forming a dimeric hexamer with distinct central and peripheral domains. Upon activation in the coagulation cascade (typically by thrombin), fibrinogen is proteolytically cleaved to form Fibrin, an insoluble polymer that constitutes the matrix of blood clots. Fibrin stabilizes the hemostatic plug, binds platelets via specific integrin receptors, and interacts with plasma proteins, growth factors, and cell surface receptors to mediate wound repair, angiogenesis, immune function, and inflammation. Disorders of Fibrinogen/Fibrin metabolism—deficiency, overactivity, or abnormal structure—are implicated in bleeding diatheses, thrombosis, cardiovascular disease, sepsis/DIC, and abnormal tissue repair or cancer. Drugs targeting Fibrin/Fibrinogen act through modulation of formation, degradation, cross-linking, or interactions with platelets and matrix proteins, with notable safety concerns in balancing hemostasis and thrombosis risk.

Other names

Fg (Fibrinogen)Fibrin precursorFibrin alpha chain (FGA)beta chain (FGB)gamma chain (FGG)Factor IPlasma fibrinogenSoluble fibrin (when in plasma prior to clotting)

Inhibit formation (preventing conversion of Fibrinogen to Fibrin by targeting thrombin or upstream cascade); Facilitate degradation (fibrinolytic drugs activating plasmin to break Fibrin clots); Stabilize clot (anti-fibrinolytic drugs bind Fibrin; Fibrin sealants act by supplementing clot matrix); Inhibit cross-linking (Factor XIIIa inhibition prevents Fibrin hardening); Enhance platelet incorporation (target the Fibrinogen-αIIbβ3 integrin interaction for platelet therapy)