Complement component 3c (C3c) (C3c)

Complement component 3c (C3c) is a stable, non-functional degradation fragment of Complement component 3 (C3), which is the central and most abundant protein of the complement system [1]. It is generated during the final stages of C3 activation and catabolism, specifically when inactivated C3b (iC3b) is further cleaved by Factor I in the presence of cofactors like Factor H or CR1 [2]. Unlike other fragments such as C3b or iC3b, C3c does not bind to cell surfaces and remains in the fluid phase (plasma or serum), making it a highly reliable clinical biomarker for assessing the degree of complement activation and consumption in various inflammatory and autoimmune conditions [3]. While C3c itself is not typically the primary pharmacological target, its parent molecule C3 is a major therapeutic target for treating diseases like paroxysmal nocturnal hemoglobinuria (PNH) and geographic atrophy [4]. Drugs such as pegcetacoplan bind to C3 and its active fragments to prevent the proteolytic cascade that leads to the formation of C3c and other potent effector molecules [5]. Monitoring C3c levels is essential for diagnosing complement-mediated disorders and evaluating the efficacy of complement-inhibiting therapies in clinical practice [6]. Sources: [1] UniProt (P01024): Complement C3 [2] StatPearls: Complement System [3] PubMed: C3c as a biomarker for complement activation [4] Ricklin et al. (2016) "Complement-targeted therapeutics" [5] FDA Label: Empaveli (pegcetacoplan) [6] Merck Manual: Complement System Diagnostics

Other names

Complement C3c fragmentC3c fragmentComplement C3c

Inhibition of Complement component 3 (C3) cleavage and activation, thereby preventing the formation of C3c and other downstream effector molecules.