Design and development of TT30, a novel C3d-targeted C3/C5 convertase inhibitor for treatment of human complement alternative pathway–mediated diseases

Fridkis-Hareli, Masha; Storek, Michael; Mazsaroff, István; Risitano, Antonio M.; Lundberg, Ante S.; Horvath, Christopher; Holers, V. Michael

doi:10.1182/blood-2011-06-359646

Cited by 112 publications

(112 citation statements)

References 30 publications

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“…This is consistent with previous data showing that the C3-opsonintargeting inhibitors mini-FH and TT30 efficiently control AP activation in several assays. 38,44,45,49,50 As observed for the double inhibition of C5 in NHS (above), addition of coversin or PAS-coversin to the patientderived, eculizumab-containing serum completely stopped the residual hemolysis if compared with eculizumab alone. We verified that the patient sera indeed contained an excess amount of eculizumab over C5 ( Figure 1F).…”

Section: Single C5 Inhibition Only Partially Blocks Tp Activationmentioning

confidence: 94%

Incomplete inhibition by eculizumab: mechanistic evidence for residual C5 activity during strong complement activation

Harder

Kuhn

Schrezenmeier

et al. 2017

Blood

118

124

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• Strong complement activation overrides the terminal pathway inhibition by the anti-C5 antibody eculizumab.• The more powerful complement is activated, the less effective is terminal pathway inhibition by diverse anti-C5 agents.Eculizumab inhibits the terminal, lytic pathway of complement by blocking the activation of the complement protein C5 and shows remarkable clinical benefits in certain complement-mediated diseases. However, several reports suggest that activation of C5 is not always completely suppressed in patients even under excess of eculizumab over C5, indicating that residual C5 activity may derogate the drug's therapeutic benefit under certain conditions. By using eculizumab and the tick-derived C5 inhibitor coversin, we determined conditions ex vivo in which C5 inhibition is incomplete. The degree of such residual lytic activity depended on the strength of the complement activator and the resulting surface density of the complement activation product C3b, which autoamplifies via the alternative pathway (AP) amplification loop. We show that at high C3b densities required for binding and activation of C5, both inhibitors reduce but do not abolish this interaction. The decrease of C5 binding to C3b clusters in the presence of C5 inhibitors correlated with the levels of residual hemolysis. However, by employing different C5 inhibitors simultaneously, residual hemolytic activity could be abolished. The importance of AP-produced C3b clusters for C5 activation in the presence of eculizumab was corroborated by the finding that residual hemolysis after forceful activation of the classical pathway could be reduced by blocking the AP. By providing insights into C5 activation and inhibition, our study delivers the rationale for the clinically observed phenomenon of residual terminal pathway activity under eculizumab treatment with important implications for anti-C5 therapy in general. (Blood. 2017;129(8):970-980)

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Section: Single C5 Inhibition Only Partially Blocks Tp Activationmentioning

confidence: 94%

Incomplete inhibition by eculizumab: mechanistic evidence for residual C5 activity during strong complement activation

Harder

Kuhn

Schrezenmeier

et al. 2017

Blood

118

124

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“…54 The FH SCR1-5 domains of the fusion protein efficiently prevent C3 convertase formation of the alternative pathway by its decay accelerating activity. 52,53 The efficacy of TT30 to inhibit alternative pathway activation at the site of complement activation has been demonstrated in haematologica | 2015; 100 (11) © F e r r a t a S t o r t i F o u n d a t i o n vitro in a hemolysis assay using rabbit RBCs. 53 Risitano and co-workers reported TT30 to efficiently inhibit C3 deposition on and hemolysis of PNH RBCs.…”

mentioning

confidence: 99%

“…© F e r r a t a S t o r t i F o u n d a t i o n vitro in a hemolysis assay using rabbit RBCs. 53 Risitano and co-workers reported TT30 to efficiently inhibit C3 deposition on and hemolysis of PNH RBCs. 55 Therefore, TT30 might be a suitable therapeutic, not only to inhibit intravascular hemolysis, but also extravascular hemolysis in PNH patients (Figure 2).…”

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confidence: 99%

“…Another elegant approach to inhibit complement activation on the level at C3 has been reported by Fridkis-Hareli and co-workers. 53 This group describes a fusion protein (TT30) linking the first 4 short consensus repeats (SCR) of human complement receptor 2 (CR2) with SCR1-5 of FH. The CR2 part of this fusion protein serves as recognition subunit for C3 degradation products (e.g.…”

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confidence: 99%

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Complement inhibitors to treat IgM-mediated autoimmune hemolysis

Wouters

2015

Haematologica

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© F e r r a t a S t o r t i F o u n d a t i o n Complement systemThe complement system is an evolutionary highly conserved cascade system that makes up part of the innate immune system. [7][8][9] Complement activation can occur via three distinct pathways (classical pathway (CP), lectin pathway (LP) and alternative pathway (AP) that converge at the level of C3 cleavage and eventually lead to a common terminal pathway (TP) ( Figure 1A).The AP can be initiated by spontaneous hydrolysis of the central complement component into C3b(H 2 O). C3b(H 2 O) is an acceptor for the next AP protein Factor B (FB) which is then cleaved by the serine protease factor D (FD), resulting Complement inhibition in AIHA haematologica | 2015; 100 (11) 1389 The lectin pathway is initiated by binding of MBL (or ficolins) to sugar structures followed by activation of C2 and C4 by MASP1/MASP2, leading to the formation of lectin C3 convertase (C2aC4b). (E) C3-activation by the classical, lectin or alternative C3 convertase results in the formation of the C5 convertase. C5 convertase subsequently activates C5 resulting in the formation of the membrane attack complex (MAC). C: complement factor; MAC: membrane attack complex; MBL: mannan binding lectin; MASP: MBL-associated serine protease; P: properdin; C1-inh: C1-inhibitor; FI: factor I; CR1: complement receptor 1; MCP: membrane co-factor protein; DAF: decay accelerating factor; C4BP: C4-binding protein; FH: factor H. A B C D E © F e r r a t a S t o r t i F o u n d a t i o nin the fluid phase C3 convertase (C3b(H 2 O)Bb), that can cleave multiple C3 molecules into C3b and C3a. C3b binds to nucleophilic targets on cell membranes 10 and C3a acts as a pro-inflammatory anaphylatoxin ( Figure 1B). Low-level activation of C3 can significantly be accelerated through a positive feedback loop resulting in the formation of additional alternative C3 convertases on the surface (C3bBb) that are stabilized by properdin (P) and eventually give rise to the formation of a C5 convertase (C3bBbC3b), which subsequently cleaves C5 into C5b and C5a.10 C5b attaches to the surface and subsequently binds to C6, C7 and C8 to form the C5bC8 complex allowing polymerization of C9 to form the membrane attack complex (MAC), which inserts into target membranes and induces cell lysis ( Figure 1A and E). 11,12 Next to lysis by the MAC, cleavage of both C3 and C5 results in the generation of pro-inflammatory anaphylatoxins (C3a, C5a) that attract and activate leukocytes 13 and C3b opsonization of the target surface facilitates uptake by phagocytic cells in the liver and spleen.During evolution complement activation became more specific by the development of recognition molecules. The CP is initiated by binding of C1q to the Fc-part of IgM or IgG complexed with their target antigens. IgM is most efficient in complement activation, due to its polymeric nature. Human IgG activates complement in the order IgG3>IgG1>IgG2, whereas IgG4 does not activate complement at all.14 As the affinity of C1q for a single IgG Fc tail is...

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“…Purified full-length FH showed efficacy in controlling the C3 convertase in a mouse model of FH deficiency (22) and in in vitro C3-deposition and cell-protection assays in the presence of aHUS-associated anti-FH autoantibodies or mutations in FH or C3 (23)(24)(25). Domains 19-20, which naturally evolved to dock FH on host cells, could be exploited in drug design to direct the regulatory activity of FH, or other complement inhibitor, to host surfaces (26). Therefore, we speculated that a minimal-size functional FH (mini-FH) could be created by directly fusing the complement regulatory domains and the host cell-recognition domains of FH.…”

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confidence: 99%

An Engineered Construct Combining Complement Regulatory and Surface-Recognition Domains Represents a Minimal-Size Functional Factor H

Hebecker

Alba-Domínguez

Roumenina

et al. 2013

The Journal of Immunology

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Complement is an essential humoral component of innate immunity; however, its inappropriate activation leads to pathology. Polymorphisms, mutations, and autoantibodies affecting factor H (FH), a major regulator of the alternative complement pathway, are associated with various diseases, including age-related macular degeneration, atypical hemolytic uremic syndrome, and C3 glomerulopathies. Restoring FH function could be a treatment option for such pathologies. In this article, we report on an engineered FH construct that directly combines the two major functional regions of FH: the N-terminal complement regulatory domains and the C-terminal surface-recognition domains. This minimal-size FH (mini-FH) binds C3b and has complement regulatory functions similar to those of the full-length protein. In addition, we demonstrate that mini-FH binds to the FH ligands C-reactive protein, pentraxin 3, and malondialdehyde epitopes. Mini-FH was functionally active when bound to the extracellular matrix and endothelial cells in vitro, and it inhibited C3 deposition on the cells. Furthermore, mini-FH efficiently inhibited complement-mediated lysis of host-like cells caused by a disease-associated FH mutation or by anti-FH autoantibodies. Therefore, mini-FH could potentially be used as a complement inhibitor targeting host surfaces, as well as to replace compromised FH in diseases associated with FH dysfunction.

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Design and development of TT30, a novel C3d-targeted C3/C5 convertase inhibitor for treatment of human complement alternative pathway–mediated diseases

Cited by 112 publications

References 30 publications

Incomplete inhibition by eculizumab: mechanistic evidence for residual C5 activity during strong complement activation

Incomplete inhibition by eculizumab: mechanistic evidence for residual C5 activity during strong complement activation

Complement inhibitors to treat IgM-mediated autoimmune hemolysis

An Engineered Construct Combining Complement Regulatory and Surface-Recognition Domains Represents a Minimal-Size Functional Factor H

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