RARE DISEASE
Complement hyperactivation-angiopathic thrombosis-protein-losing enteropathy syndrome
Complement hyperactivation-angiopathic thrombosis-protein-losing enteropathy syndrome
Complement hyperactivation-angiopathic thrombosis-protein-losing enteropathy syndrome
Synonyms: CD55 deficiency, CHAPLE syndrome
Synonyms: CD55 deficiency, CHAPLE syndrome
Synonyms: CD55 deficiency, CHAPLE syndrome
Drug discovery
1
drug
With orphan designation
Overview
Complement hyperactivation-angiopathic thrombosis-protein-losing enteropathy (CHAPLE) syndrome is an ultra-rare autosomal recessive disorder caused by biallelic CD55 mutations, resulting in impaired complement regulation. This leads to systemic complement hyperactivation, lymphatic intestinal damage, and protein-losing enteropathy. Clinical features include abdominal pain, vomiting, diarrhea, hypoproteinemic edema, malnutrition, recurrent infections (due to hypogammaglobulinemia), and life-threatening thromboembolic events [1][3][8]. Diagnosis is confirmed via genetic testing and low serum CD55 expression [6][8].
Burden
Mortality: 20% risk of fatal thromboembolism without treatment [6][8]
Morbidity: Growth failure (100%), chronic anemia (91%), and recurrent hospitalizations for hypoalbuminemia/infections [1][6]
Quality of life: Severe GI dysfunction limits oral intake and daily activities, with 70% requiring transfusions pre-treatment [6][8]
Therapies
Targeted therapy: Pozelimab (C5 inhibitor) – FDA-approved first-line treatment showing serum albumin normalization and symptom resolution [7][8]
Supportive care: Albumin infusions, immunoglobulin replacement, anticoagulants, and nutritional support (less effective without complement inhibition) [3][6]
Investigational: Eculizumab (anti-C5 monoclonal antibody) demonstrated efficacy in early trials [3][6]
Categories: rare gastroenterological diseases, rare genetic diseases, rare transplant-related disorders
Research Papers
108 drug discovery papers about Complement hyperactivation-angiopathic thrombosis-protein-losing enteropathy syndrome, with 1 first-in-class and 2 next-in-class emerging drug candidates forecasted to outperform the average preclinical success rate. Recent publications:
108 drug discovery papers about Complement hyperactivation-angiopathic thrombosis-protein-losing enteropathy syndrome, with 1 first-in-class and 2 next-in-class emerging drug candidates forecasted to outperform the average preclinical success rate. Recent publications:
categories:
Small molecules
gene therapies
2022-06-10 | A desirable transgenic strategy using GGTA1 endogenous promoter-mediated knock-in for xenotransplantation model
Abstract Pig-to-human organ transplantation is a feasible solution to resolve the shortage of organ donors for patients that wait for transplantation. To overcome immunological rejection, which is the main hurdle in pig-to-human xenotransplantation, various engineered transgenic pigs have been developed. Ablation of xeno-reactive antigens, especially the 1,3-Gal epitope (GalT), which causes hyperacute rejection, and insertion of complement regulatory protein genes, such as hCD46, hCD55, and hCD59, and genes to regulate the coagulation pathway or immune cell-mediated rejection may be required for an ideal xenotransplantation model. However, the technique for stable and efficient expression of multi-transgenes has not yet been settled to develop a suitable xenotransplantation model. To develop a stable and efficient transgenic system, we knocked-in internal ribosome entry sites (IRES)-mediated transgenes into the α 1,3-galactosyltransferase (GGTA1) locus so that expression of these transgenes would be controlled by the GGTA1 endogenous promoter. We constructed an IRES-based polycistronic hCD55/hCD39 knock-in vector to target exon4 of the GGTA1 gene. The hCD55/hCD39 knock-in vector and CRISPR/Cas9 to target exon4 of the GGTA1 gene were co-transfected into white yucatan miniature pig fibroblasts. After transfection, hCD39 expressed cells were sorted by FACS. Targeted colonies were verified using targeting PCR and FACS analysis, and used as donors for somatic cell nuclear transfer. Expression of GalT, hCD55, and hCD39 was analyzed by FACS and western blotting. Human complement-mediated cytotoxicity and human antibody binding assays were conducted on peripheral blood mononuclear cells (PBMCs) and red blood cells (RBCs), and deposition of C3 by incubation with human complement serum and platelet aggregation were analyzed in GGTA1 knock-out (GTKO)/CD55/CD39 pig cells. We obtained six targeted colonies with high efficiency of targeting (42.8% of efficiency). Selected colony and transgenic pigs showed abundant expression of targeted genes (hCD55 and hCD39). Knocked-in transgenes were expressed in various cell types under the control of the GGTA1 endogenous promoter in GTKO/CD55/CD39 pig and IRES was sufficient to express downstream expression of the transgene. Human IgG and IgM binding decreased in GTKO/CD55/CD39 pig and GTKO compared to wild-type pig PBMCs and RBCs. The human complement-mediated cytotoxicity of RBCs and PBMCs decreased in GTKO/CD55/CD39 pig compared to cells from GTKO pig. C3 was also deposited less in GTKO/CD55/CD39 pig cells than wild-type pig cells. The platelet aggregation was delayed by hCD39 expression in GTKO/CD55/CD39 pig. In the current study, knock-in into the GGTA1 locus and GGTA1 endogenous promoter-mediated expression of transgenes are an appropriable strategy for effective and stable expression of multi-transgenes. The IRES-based polycistronic transgene vector system also caused sufficient expression of both hCD55 and hCD39. Furthermore, co-transfection of CRISPR/Cas9 and the knock-in vector not only increased the knock-in efficiency but also induced null for GalT by CRISPR/Cas9-mediated double-stranded break of the target site. As shown in human complement-mediated lysis and human antibody binding to GTKO/CD55/CD39 transgenic pig cells, expression of hCD55 and hCD39 with ablation of GalT prevents an effective immunological reaction in vitro. As a consequence, our technique to produce multi-transgenic pigs could improve the development of a suitable xenotransplantation model, and the GTKO/CD55/CD39 pig developed could prolong the survival of pig-to-primate xenotransplant recipients.
2019-04-30 | Generation of GTKO Diannan Miniature Pig Expressing Human Complementary Regulator Proteins hCD55 and hCD59 via T2A Peptide-Based Bicistronic Vectors and SCNT.
Pig-to-human organ transplantation has drawn attention in recent years due to the potential use of pigs as an alternative source of human donor organs. While GGTA1 knockout (GTKO) can protect xenografts from hyperacute rejection, complement-dependent cytotoxicity might still contribute to this type of rejection. To prolong the xenograft survival, we utilized a T2A-mediated pCMV-hCD55-T2A-hCD59-Neo vector and transfected the plasmid into GTKO Diannan miniature pig fetal fibroblasts. After G418 selection combined with single-cell cloning culture, four colonies were obtained, and three of these were successfully transfected with the hCD55 and hCD59. One of the three colonies was selected as donor cells for somatic cell nuclear transfer (SCNT). Then, the reconstructed embryos were transferred into eight recipient gilts, resulting in four pregnancies. Three of the pregnant gilts delivered, yielding six piglets. Only one piglet carried hCD55 and hCD59 genetic modification. The expression levels of the GGTA1, hCD55, and hCD59 in the tissues and fibroblasts of the piglet were determined by q-PCR, fluorescence microscopy, immunohistochemical staining, and western blotting analyses. The results showed the absence of GGTA1 and the coexpression of the hCD55 and hCD59. However, the mRNA expression levels of hCD55 and hCD59 in the GTKO/hCD55/hCD59 pig fibroblasts were lower than that in human 293T cells, which may be caused by low copy number and/or CMV promoter methylation. Furthermore, we performed human complement-mediated cytolysis assays using human serum solutions from 0 to 60%. The result showed that the fibroblasts of this triple-gene modified piglet had greater survival rates than that of wild-type and GTKO controls. Taken together, these results indicate that T2A-mediated polycistronic vector system combined with SCNT can effectively generate multiplex genetically modified pigs, additional hCD55 and hCD59 expression on top of a GTKO genetic background markedly enhance the protective effect towards human serum-mediated cytolysis than those of GTKO alone. Thus, we suggest that GTKO/hCD55/hCD59 triple-gene-modified Diannan miniature pig will be a more eligible donor for xenotransplantation.
2015-04-28 | Adeno-associated virus mediated delivery of an engineered protein that combines the complement inhibitory properties of CD46, CD55 and CD59
Background A variety of disorders are associated with the activation of complement. CD46, CD55 and CD59 are the major membrane associated regulators of complement on human cells. Previously, we have found that independent expression of CD55, CD46 or CD59 through gene transfer protects murine tissues against human complement mediated attack. In the present study, we investigated the potential of combining the complement regulatory properties of CD46, CD55 and CD59 into single gene products expressed from an adeno-associated virus (AAV) vector in a soluble non-membrane anchored form. Methods Minigenes encoding the complement regulatory domains from CD46, CD55 and CD59 (SACT) or CD55 and CD59 (DTAC) were cloned into an AAV vector. The specific regulatory activity of each component of SACT and DTAC was measured in vitro. The recombinant AAV vectors were injected into the peritoneum of mice and the efficacy of the transgene products for being able to protect murine liver vasculature against human complement, specifically the membrane attack complex (MAC), was measured. Results SACT and DTAC exhibited properties similar to CD46, CD55 and CD59 or CD55 and CD59, respectively, in vitro. AAV mediated delivery of SACT or DTAC protected murine liver vasculature from human MAC deposition by 63.2% and 56.7%, respectively. Conclusions When delivered to mice in vivo via an AAV vector, SACT and DTAC are capable of limiting human complement mediated damage. SACT and DTAC merit further study as potential therapies for complement mediated disorders when delivered via a gene therapy approach. Copyright © 2015 John Wiley & Sons, Ltd.
2012-05-11 | Human CD55 expression blocks hyperacute rejection and restricts complement activation in Gal knockout cardiac xenografts.
Transgenic expression of human complement regulatory proteins reduces the frequency of hyperacute rejection (HAR) in Gal-positive cardiac xenotransplantation. In this study, we examined the impact of human CD55 (hCD55) expression on a Gal knockout (GTKO) background using pig-to-primate heterotopic cardiac xenotransplantation. Cardiac xenotransplantation was performed with GTKO (group 1; n=6) and GTKO.hCD55 (group 2; n=5) donor pigs using similar immunosuppression. Cardiac biopsies were obtained 30 min after organ reperfusion. Rejection was characterized by histology and immunohistology. Intragraft gene expression, serum non-Gal antibody, and antibody recovered from rejected hearts were analyzed. HAR of a GTKO heart was observed. Remaining grafts developed delayed xenograft rejection. Median survival was 21 and 28 days for groups 1 and 2, respectively. Vascular antibody deposition was uniformly detected 30 min after organ reperfusion and at explant. A higher frequency of vascular C5b deposition was seen in GTKO organs at explant. Serum non-Gal antibody, antibody recovered from the graft, and intragraft gene expression were similar between the groups. HAR of GTKO hearts without hCD55 may occur. Expression of hCD55 seemed to restrict local complement activation but did not improve graft survival. Chronic vascular antibody deposition with evidence of protracted endothelial cell activation was seen. These observations suggest that non-Gal antibody-induced chronic endothelial cell activation coupled to possible hemostatic incompatibilities may be the primary stimulus for delayed xenograft rejection of GTKO hearts. To avoid possible HAR, future clinical studies should use donors expressing human complement regulatory proteins in the GTKO background.
2010-11-02 | Adenovirus capsid-display of the retro-oriented human complement inhibitor DAF reduces Ad vector-triggered immune responses in vitro and in vivo.
Adenovirus (Ad) vectors are widely used in human clinical trials. However, at higher dosages, Ad vector-triggered innate toxicities remain a major obstacle to many applications. Ad interactions with the complement system significantly contribute to innate immune responses in several models of Ad-mediated gene transfer. We constructed a novel class of Ad vectors, genetically engineered to "capsid-display" native and retro-oriented versions of the human complement inhibitor decay-accelerating factor (DAF), as a fusion protein from the C-terminus of the Ad capsid protein IX. In contrast to conventional Ad vectors, DAF-displaying Ads dramatically minimized complement activation in vitro and complement-dependent immune responses in vivo. DAF-displaying Ads did not trigger thrombocytopenia, minimized endothelial cell activation, and had diminished inductions of proinflammatory cytokine and chemokine responses. The retro-oriented display of DAF facilitated the greatest improvements in vivo, with diminished activation of innate immune cells, such as dendritic and natural killer cells. In conclusion, Ad vectors can capsid-display proteins in a manner that not only retains the functionality of the displayed proteins but also potentially can be harnessed to improve the efficacy of this important gene transfer platform for numerous gene transfer applications.
proteins
2023-10-25 | The monosialoganglioside GM1a protects against complement attack
The complement system is a part of the innate immune system in the fluid phase and efficiently eliminates pathogens. However, its activation requires tight regulation on the host cell surface in order not to compromise cellular viability. Previously, we showed that loss of placental cell surface sialylation in mice in vivo leads to a maternal complement attack at the fetal-maternal interface, ultimately resulting in loss of pregnancy. To gain insight into the regulatory function of sialylation in complement activation, we here generated trophoblast stem cells (TSC) devoid of sialylation, which also revealed complement sensitivity and cell death in vitro. Glycolipid-analysis by multiplexed capillary gel electrophoresis coupled to laser-induced fluorescence detection (xCGE-LIF) allowed us to identify the monosialoganglioside GM1a as a key element of cell surface complement regulation. Exogenously administered GM1a integrated into the plasma membrane of trophoblasts, substantially increased binding of complement factor H (FH) and was sufficient to protect the cells from complement attack and cell death. GM1a treatment also rescued human endothelial cells and erythrocytes from complement attack in a concentration dependent manner. Furthermore, GM1a significantly reduced complement mediated hemolysis of erythrocytes from a patient with Paroxysmal nocturnal hemoglobinuria (PNH). This study demonstrates the complement regulatory potential of exogenously administered gangliosides and paves the way for sialoglycotherapeutics as a novel substance class for membrane-targeted complement regulators.
2022-01-10 | Hemopexin Modulates Expression of Complement Regulatory Proteins in Rat Glomeruli.
In systemic hemolysis and in hematuric forms of kidney injury, the major heme scavenging protein, hemopexin (HPX), becomes depleted, and the glomerular microvasculature (glomeruli) is exposed to high concentrations of unbound heme, which, in addition to causing oxidative injury, can activate complement cascades; thus, compounding extent of injury. It is unknown whether unbound heme can also activate specific complement regulatory proteins that could defend against complement-dependent injury. Isolated rat glomeruli were incubated in media supplemented with HPX-deficient (HPX-) or HPX-containing (HPX+) sera as a means of achieving different degrees of heme partitioning between incubation media and glomerular cells. Expression of heme oxygenase (HO)-1 and of the complement activation inhibitors, decay-accelerating factor (DAF), CD59, and complement receptor-related gene Y (Crry), was assessed by western blot analysis. Expression of HO-1 and of the GPI-anchored DAF and CD59 proteins increased in isolated glomeruli incubated with HPX- sera with no effect on Crry expression. Exogenous heme (hemin) did not further induce DAF but increased Crry expression. HPX modulates heme-mediated induction of complement activation controllers in glomeruli. This effect could be of translational relevance in glomerular injury associated with hematuria.
2019-08-30 | Combining MAP‐1:CD35 or MAP‐1:CD55 fusion proteins with pattern‐recognition molecules as novel targeted modulators of the complement cascade
Dysregulation of the complement system is involved in the pathogenesis of several diseases, and its inhibition has been shown to be a feasible therapeutic option. Therefore, there is an interest in the development of complement modulators to treat complement activation-related inflammatory pathologies. Mannose-binding lectin (MBL)/ficolin/collectin-associated protein-1 (MAP-1) is a regulatory molecule of the lectin pathway (LP), whereas complement receptor 1 (CD35) and decay-accelerating factor (CD55) are membrane-anchored regulators with effects on the central effector molecule C3. In this study, we developed 2 novel soluble chimeric inhibitors by fusing MAP-1 to the 3 first domains of CD35 (CD351-3) or the 4 domains of CD55 (CD551-4) to modulate the complement cascade at 2 different stages. The constructs showed biologic properties similar to those of the parent molecules. In functional complement activation assays, the constructs were very efficient in inhibiting LP activation at the level of C3 and in the formation of terminal complement complex. This activity was enhanced when coincubated with recombinant LP recognition molecules MBL and ficolin-3. Recombinant MAP-1 fusion proteins, combined with recombinant LP recognition molecules to target sites of inflammation, represent a novel and effective therapeutic approach involving the initiation and the central and terminal effector functions of the complement cascade.-Pérez-Alós, L., Bayarri-Olmos, R., Skjoedt, M.-O., Garred, P. Combining MAP-1:CD35 or MAP-1:CD55 fusion proteins with pattern-recognition molecules as novel targeted modulators of the complement cascade.
2017-05-13 | Overexpression of Human CD55 and CD59 or Treatment with Human CD55 Protects against Renal Ischemia-Reperfusion Injury in Mice
Abstract Deficiency in the membrane-bound complement regulators CD55 and CD59 exacerbates renal ischemia-reperfusion injury (IRI) in mouse models, but the effect of increasing CD55 and CD59 activity has not been examined. In this study, we investigated the impact of overexpression of human (h) CD55 ± hCD59 or treatment with soluble rhCD55 in a mouse model of renal IRI. Unilaterally nephrectomised mice were subjected to 18 (mild IRI) or 22 min (moderate IRI) warm renal ischemia, and analyzed 24 h after reperfusion for renal function (serum creatinine and urea), complement deposition (C3b/c and C9), and infiltration of neutrophils and macrophages. Transgenic mice expressing hCD55 alone were protected against mild renal IRI, with reduced creatinine and urea levels compared with wild type littermates. However, the renal function of the hCD55 mice was not preserved in the moderate IRI model, despite a reduction in C3b/c and C9 deposition and innate cell infiltration. Mice expressing both hCD55 and hCD59, on the other hand, were protected in the moderate IRI model, with significant reductions in all parameters measured. Wild type mice treated with rhCD55 immediately after reperfusion were also protected in the moderate IRI model. Thus, manipulation of CD55 activity to increase inhibition of the C3 and C5 convertases is protective against renal IRI, and the additional expression of hCD59, which regulates the terminal complement pathway, provides further protection. Therefore, anti-complement therapy using complement regulatory proteins may provide a potential clinical option for preventing tissue and organ damage in renal IRI.
2014-08-11 | A novel CRIg‐targeted complement inhibitor protects cells from complement damage
The inappropriate activation of complement may contribute to various immune diseases. The alternative pathway (AP) predominates during complement activation regardless of the initiating pathways. Hence, the main AP regulator factor H (FH) holds great potential as an attractive therapeutic intervention. In addition, complement receptor of the immunoglobulin superfamily (CRIg) has been demonstrated to inhibit AP and, more notably, still specifically binds to C3b/iC3b. We thus developed novel CRIg-targeted complement inhibitors by connecting the functional domains of CRIg and FH, which we termed CRIg-FH and CRIg-L-FH. CRIg-L-FH, slightly more potent than CRIg-FH, considerably inhibited both AP- and also classical pathway (CP)-mediated hemolysis and successfully eliminated the deposition of C3b/iC3b. Kinetic analysis further revealed that the binding affinity constant (KD) of CRIg/FH was in the micromolar range, consistent with its long-lasting binding to complement-attacked cells. CRIg-L-FH efficiently protected aberrant erythrocytes of patients with paroxysmal nocturnal hemoglobinuria (PNH) from AP-and CP-mediated complement damage (IC50 was 22.43 and 64.69 nM, respectively). Moreover, CRIg-L-FH was found to inhibit complement activation induced by the anti-Thy1 antibody in a mesangiopro-liferative glomerulonephritis (MPGN) rat model. Hence, CRIg-L-FH protects glomerular mesangial cells (GMCs) from complement-mediated injury and proliferative lesions. These findings strongly suggest that CRIg/FH is a potential therapeutic drug candidate for a range of complement-mediated diseases.—Qiao, Q., Teng, X., Wang, N., Lu, R., Guo, L., Zhang, X., Du, Y., Wang, W., Chen, S., Wu, Q., He, G., Wang, Y., and Hu, W., A novel CRIg-targeted complement inhibitor protects cells from complement damage. FASEB J. 28, 4986–4999 (2014). www.fasebj.org
small molecules
2023-03-10 | SAR443809: a selective inhibitor of the complement alternative pathway, targeting complement factor Bb
Dysregulated activation of the complement system is implicated in the onset or progression of several diseases. Most clinical-stage complement inhibitors target the inactive complement proteins present at high concentrations in plasma, which increases target-mediated drug disposition and necessitates high drug levels to sustain therapeutic inhibition. Furthermore, many efforts are aimed at inhibiting only terminal pathway activity, which leaves opsonin-mediated effector functions intact. We describe the discovery of SAR443809, a specific inhibitor of the alternative pathway C3/C5 convertase (C3bBb). SAR443809 selectively binds to the activated form of factor B (factor Bb) and inhibits alternative pathway activity by blocking the cleavage of C3, leaving the initiation of classical and lectin complement pathways unaffected. Ex vivo experiments with patient-derived paroxysmal nocturnal hemoglobinuria erythrocytes show that, although terminal pathway inhibition via C5 blockade can effectively inhibit hemolysis, proximal complement inhibition with SAR443809 inhibits both hemolysis and C3b deposition, abrogating the propensity for extravascular hemolysis. Finally, intravenous and subcutaneous administration of the antibody in nonhuman primates demonstrated sustained inhibition of complement activity for several weeks after injection. Overall, SAR443809 shows strong potential for treatment of alternative pathway-mediated disorders.
2022-04-19 | Mathematical Modeling of Complement Pathway Dynamics for Target Validation and Selection of Drug Modalities for Complement Therapies
Motivation: The complement pathway plays a critical role in innate immune defense against infections. Dysregulation between activation and regulation of the complement pathway is widely known to contribute to several diseases. Nevertheless, very few drugs that target complement proteins have made it to the final regulatory approval because of factors such as high concentrations and dosing requirements for complement proteins and serious side effects from complement inhibition. Methods: A quantitative systems pharmacology (QSP) model of the complement pathway has been developed to evaluate potential drug targets to inhibit complement activation in autoimmune diseases. The model describes complement activation via the alternative and terminal pathways as well as the dynamics of several regulatory proteins. The QSP model has been used to evaluate the effect of inhibiting complement targets on reducing pathway activation caused by deficiency in factor H and CD59. The model also informed the feasibility of developing small-molecule or large-molecule antibody drugs by predicting the drug dosing and affinity requirements for potential complement targets. Results: Inhibition of several complement proteins was predicted to lead to a significant reduction in complement activation and cell lysis. The complement proteins that are present in very high concentrations or have high turnover rates (C3, factor B, factor D, and C6) were predicted to be challenging to engage with feasible doses of large-molecule antibody compounds (≤20 mg/kg). Alternatively, complement fragments that have a short half-life (C3b, C3bB, and C3bBb) were predicted to be challenging or infeasible to engage with small-molecule compounds because of high drug affinity requirements (>1 nM) for the inhibition of downstream processes. The drug affinity requirements for disease severity reduction were predicted to differ more than one to two orders of magnitude than affinities needed for the conventional 90% target engagement (TE) for several proteins. Thus, the QSP model analyses indicate the importance for accounting for TE requirements for achieving reduction in disease severity endpoints during the lead optimization stage.
2019-04-04 | Polyphosphates and Complement Activation
To sustain life in environments that are fraught with risks of life-threatening injury, organisms have developed innate protective strategies such that the response to wounds is rapid and localized, with the simultaneous recruitment of molecular, biochemical and cellular pathways that limit bleeding and eliminate pathogens and damaged host cells, while promoting effective healing. These pathways are tightly regulated, as their over- or under-activation may lead to inadequate healing, disease, and/or demise of the host. Recent advances in our understanding of coagulation and complement, a key component of innate immunity, have revealed critical molecular links that regulate the delicate balance of both systems, thereby providing the necessary elements to achieve homeostasis. Polyphosphate is one such factor that intriguingly, plays a key role by promoting coagulation, while dampening complement activation, a discovery that is uncovering novel insights into mechanisms underlying disease and new therapeutic strategies.
2017-08-16 | Heme Oxygenase 1 Up-Regulates Glomerular Decay Accelerating Factor Expression and Minimizes Complement Deposition and Injury.
Complement-activation controllers, including decay accelerating factor (DAF), are gaining emphasis as they minimize injury in various dysregulated complement-activation disorders, including glomerulopathies. Heme oxygenase (HO)-1 overexpression or induction has been shown to attenuate injury in complement-dependent models of glomerulonephritis. This study investigated whether up-regulation of DAF by heme oxygenase 1 (HO-1) is an underlying mechanism by using Hmox-1-deficient rats (Hmox1+/-; Hmox1-/-) or rats with HO-1 overexpression targeted to glomerular epithelial cells (GECHO-1), which are particularly vulnerable to complement-mediated injury owing to their terminally differentiated nature. Constitutively expressed DAF was decreased in glomeruli of Hmox1-/- rats and augmented in glomeruli of GECHO-1 rats. In GECHO-1 rats with anti-glomerular basement membrane antibody mediated, complement-dependent injury, complement component C3 fragment b (C3b) deposition was reduced, whereas proteinuria was diminished. In glomeruli of wild-type rats, the natural Hmox substrate, hemin, induced glomerular DAF. This effect was attenuated in glomeruli of Hmox1-/- rats and augmented in glomeruli of GECHO-1 rats. Hemin analogues differing in either metal or porphyrin ring functionalities, acting as competitive Hmox-substrate inhibitors, also increased glomerular DAF and reduced C3b deposition after spontaneous complement activation. In the presence of a DAF-blocking antibody, the reduction in C3b deposition was reversed. These observations establish HO-1 as a physiologic regulator of glomerular DAF and identify hemin analogues as inducers of functional glomerular DAF able to minimize C3b deposition.
2017-02-10 | Complement’s hidden arsenal: New insights and novel functions inside the cell
A key component of both innate and adaptive immunity, new understandings of the complement system are expanding its roles beyond that traditionally appreciated. Evidence is accumulating that complement has an intracellular arsenal of components that provide not only immune defense, but also assist in key interactions for host cell functions. Although early work has primarily centered on T cells, the intracellular complement system likely functions in many if not most cells of the body. Some of these functions may trace their origins to the primitive complement system that began as a primeval form of C3 likely tasked for protection from intracellular pathogen invasion. This later expanded to include extracellular defense as C3 became a secreted protein to patrol the vasculature. Other components were added to the growing system including regulators to protect host cells from the indiscriminate effects of this potent system. Contemporary cells may retain some of these vestigial remnants. We now know that a) C3 serves as a damage-associated molecular pattern (in particular by coating pathogens that translocate into cells), b) most cells store C3 and recycle C3(H2O) for immediate use, and c) C3 assists in cellular survival and metabolic reprogramming. Other components also are part of this hidden arsenal including C5, properdin, factors H and B, and complement receptors. Importantly, better definition of the intracellular complement system may translate into new target discovery to assist in creating the next generation of complement therapeutics.
antibodies
2026-08-17 | Targeted complement inhibition with pozelimab in children with CD55 deficiency.
CHAPLE syndrome is an ultra-rare genetic cause of protein-losing enteropathy (PLE) resulting from uncontrolled complement activation due to CD55 deficiency. We report two paediatric patients presenting with recurrent diarrhoea, hypoalbuminaemia, hypogammaglobulinaemia and growth failure, both initially evaluated as intestinal lymphangiectasia. Persistent symptoms and poor response to conventional therapy prompted genetic evaluation, which revealed pathogenic variants in the CD55 gene in both children, confirming the diagnosis of CHAPLE syndrome. Both patients required repeated albumin and intravenous immunoglobulin replacement prior to diagnosis. Targeted therapy with pozelimab was initiated. Rapid clinical and biochemical improvement was observed within 2 weeks, with sustained normalisation of albumin, total protein and immunoglobulin levels. At 3-month follow-up, both children remained in clinical remission without further need for albumin or immunoglobulin infusions. These cases highlight the importance of considering genetic causes in children with refractory PLE and demonstrate the effectiveness of early targeted complement inhibition in CHAPLE syndrome.
2026-05-28 | C5 inhibition restores B cell homeostasis and humoral immunity in CHAPLE disease patients.
CHAPLE disease is a monogenic disorder in which CD55 deficiency drives gastrointestinal pathology. How CD55 deficiency affects adaptive immunity is unknown. Herein, molecularly, we characterize eight patients with genetically novel CD55 deficiency. Clinically, all patients developed early-onset protein-losing enteropathy, frequently complicated by thrombotic events, inflammatory bowel disease-like lesions, and recurrent respiratory infections. Ex vivo, immunophenotyping revealed disruption of the B cell compartment, marked by depletion of transitional B cells, expansion of CD21lo B cells, and accumulation of class-switched memory B cells and plasmablasts, while T cell subsets were largely preserved. In vivo, eculizumab rapidly resolved intestinal pathology, normalized serum albumin and immunoglobulin levels, and re-established a normal B cell profile. Furthermore, C5 inhibition enabled effective humoral protection and optimal pneumococcal vaccine responses. Together, these findings establish complement inhibition as central to B cell homeostasis in CHAPLE disease.
2026-04-01 | P15 When N <100: compassionate use of a novel therapy in CHAPLE syndrome
C H A P L E syndrome (CD55 deficiency) is an ultra-rare primary immunodeficiency, with fewer than 100 cases reported globally. 1 A paediatric patient at a tertiary paediatric centre in the United Kingdom was granted compassionate access to pozelimab, a novel monoclonal antibody imported from the United States. Delivering this treatment required close multidisciplinary collaboration between the consultant immunologist, specialist nurse, and pharmacy teams, including clinical, quality assurance, and procurement.The pharmacy team ensured the clinical appropriateness of the treatment through independent evaluation of the patient’s condition and the available evidence. In the absence of established protocols or reference sources, they implemented clinical governance measures to support safe prescribing and administration, including documentation, dosing guidance, and risk mitigation strategies. Pharmacists played an active role in patient and family engagement, providing education and counselling to support informed decision-making. In parallel, the pharmacy team also managed regulatory liaison, importation, and arrangements for continued supply.An online meeting was held with the patient and parent to explore their perspectives on the compassionate use process. The patient, who had previously received immunosuppressants including biologics, expressed relief at finally having a confirmed diagnosis and a treatment specifically targeting her condition. Although initially concerned about side effects, she understood the associated risks from prior experience and felt reassured. She preferred receiving verbal information from the consultant, nurse, and pharmacist but felt written material would be helpful for future reference. She was surprised that the medication came in a vial rather than a prefilled pen or syringe but ultimately preferred the vial and appreciated the team’s efforts to explore pain-minimising techniques that worked for her.The parent also expressed relief at the diagnosis, but noted difficulty accessing peer support or patient experiences due to the rarity of the condition. Despite receiving written materials and links to the manufacturer’s website, she felt reading about others’ experiences would have offered greater reassurance when deciding to start treatment. She highly praised the multidisciplinary approach and the effectiveness of communication across the team. The pharmacist’s presence during the first administration was particularly valued, though she suggested earlier pharmacy involvement—ideally when the drug was first proposed in clinic—would have been beneficial. She also identified a need for more lifestyle and dietary guidance to support ongoing care. Overall, both parent and patient felt supported in their decision to begin treatment and expressed high satisfaction with the pharmacy team’s contribution and the collaborative approach.Conclusion Delivering compassionate use treatment for ultra-rare diseases requires coordinated, multidisciplinary care. The input of the consultant, nurse, and pharmacy teams was central to supporting the family and ensuring treatment was initiated safely. This case highlights the importance of early pharmacy involvement, structured governance processes, and person-centred communication. Patient and parent feedback reinforced the value of accessible information and the reassurance provided by collaborative, transparent care in the context of rare disease management.Reference Litcher-Kelly L, Ozen A, Ollis S, et al. The patient experience of CHAPLE disease: results from interviews conducted as part of a clinical trial for an ultra-rare condition. Orphanet Journal of Rare Diseases 2025;20:68.
2026-03-24 | Evaluating pozelimab in the treatment of CHAPLE disease.
CHAPLE disease (Complement Hyperactivation, Angiopathic Thrombosis, and Protein-Losing Enteropathy [PLE]) is a rare, life-threatening disorder caused by biallelic mutations in the CD55 gene, which encodes decay-accelerating factor, a key regulator of the complement system. The disease typically manifests in early childhood with hypoalbuminemic edema, gastrointestinal symptoms, recurrent infections, and failure to thrive, alongside an elevated thrombotic risk due to complement-mediated endothelial injury and coagulation activation. Given these pathogenetic mechanisms, complement-targeted therapies have emerged as a rational approach to disease management. Eculizumab, a monoclonal antibody against complement component C5, initially demonstrated clinical benefit when administered on a compassionate-use basis. Building upon this success, pozelimab, a next-generation subcutaneous anti-C5 monoclonal antibody, was evaluated in CHAPLE patients and subsequently received U.S. FDA approval for this indication. Pozelimab effectively inhibits terminal complement activation, leading to sustained remission of PLE, obviating the need for albumin replacement, reducing hospitalization rates, improving symptom control and nutritional status, and ultimately enhancing overall quality of life. This review highlights the evolving role of pozelimab in CHAPLE disease by discussing its mechanistic basis, emerging clinical evidence, and implications for patient-centered care.
2025-11-22 | The Critical Role of Biochemical and Genetic Diagnosis in Differentiating CHAPLE Syndrome from Treatment-Resistant IBD: A Case Study
Background: CHAPLE syndrome (Complement Hyperactivation, Angiopathic Thrombosis, and Protein-Losing Enteropathy) is an extremely rare and life-threatening monogenic disease caused by loss-of-function mutations of CD55 leading to dysregulation of the alternative complement pathway. The clinical pattern characterized by PLE and chronic inflammatory disease is frequently misattributed to idiopathic bowel disease (IBD) with consequent inappropriate and prolonged treatment with immunosuppressive drugs. Methods: We report on a 6-year-old boy with early-onset chronic diarrhea, failure to thrive and steroid-dependent PLE that was initially identified as IBD. To resolve the diagnostic confusion, a fulminant biochemical and genetic lookups were performed. Results: This patient's sustained biochemical abnormalities severe hypoalbuminemia (15-22 g/L), profound thrombocytosis (platelets> 800 x 10⁹/l) and dimorphic anaemia were unrelated to traditional IBD. Genetic central sequencing demonstrated a homozygous deleterious CD55 variant, confirming the diagnosis of CHAPLE syndrome. This diagnosis provided the pathophysiological explanation for complement activation. Discussion: Treatment was consequently changed from corticosteroids to pozelimab, a complement C5 inhibitor monoclonal antibody. This therapy resulted in a prompt normalization of serum albumin and relief from gastrointestinal symptoms with subsequent prolonged clinical remission. Conclusions: We report a case, which highlights that a particular combination of biochemical aberrations in a previously well individual with refractory IBD should bring to mind monogenic causes including CHAPLE syndrome. Genetic testing is the best and most accurate way to diagnose a disorder. It is a revolution in the treatment of disease: away from nonspecific suppression of the immune system and toward targeted biologic therapy aimed at its precise cause — with dramatically better outcomes. Identification of these patterns and advising on confirmatory testing is a responsibility of clinical biochemists.
gene therapies
2022-06-10 | A desirable transgenic strategy using GGTA1 endogenous promoter-mediated knock-in for xenotransplantation model
Abstract Pig-to-human organ transplantation is a feasible solution to resolve the shortage of organ donors for patients that wait for transplantation. To overcome immunological rejection, which is the main hurdle in pig-to-human xenotransplantation, various engineered transgenic pigs have been developed. Ablation of xeno-reactive antigens, especially the 1,3-Gal epitope (GalT), which causes hyperacute rejection, and insertion of complement regulatory protein genes, such as hCD46, hCD55, and hCD59, and genes to regulate the coagulation pathway or immune cell-mediated rejection may be required for an ideal xenotransplantation model. However, the technique for stable and efficient expression of multi-transgenes has not yet been settled to develop a suitable xenotransplantation model. To develop a stable and efficient transgenic system, we knocked-in internal ribosome entry sites (IRES)-mediated transgenes into the α 1,3-galactosyltransferase (GGTA1) locus so that expression of these transgenes would be controlled by the GGTA1 endogenous promoter. We constructed an IRES-based polycistronic hCD55/hCD39 knock-in vector to target exon4 of the GGTA1 gene. The hCD55/hCD39 knock-in vector and CRISPR/Cas9 to target exon4 of the GGTA1 gene were co-transfected into white yucatan miniature pig fibroblasts. After transfection, hCD39 expressed cells were sorted by FACS. Targeted colonies were verified using targeting PCR and FACS analysis, and used as donors for somatic cell nuclear transfer. Expression of GalT, hCD55, and hCD39 was analyzed by FACS and western blotting. Human complement-mediated cytotoxicity and human antibody binding assays were conducted on peripheral blood mononuclear cells (PBMCs) and red blood cells (RBCs), and deposition of C3 by incubation with human complement serum and platelet aggregation were analyzed in GGTA1 knock-out (GTKO)/CD55/CD39 pig cells. We obtained six targeted colonies with high efficiency of targeting (42.8% of efficiency). Selected colony and transgenic pigs showed abundant expression of targeted genes (hCD55 and hCD39). Knocked-in transgenes were expressed in various cell types under the control of the GGTA1 endogenous promoter in GTKO/CD55/CD39 pig and IRES was sufficient to express downstream expression of the transgene. Human IgG and IgM binding decreased in GTKO/CD55/CD39 pig and GTKO compared to wild-type pig PBMCs and RBCs. The human complement-mediated cytotoxicity of RBCs and PBMCs decreased in GTKO/CD55/CD39 pig compared to cells from GTKO pig. C3 was also deposited less in GTKO/CD55/CD39 pig cells than wild-type pig cells. The platelet aggregation was delayed by hCD39 expression in GTKO/CD55/CD39 pig. In the current study, knock-in into the GGTA1 locus and GGTA1 endogenous promoter-mediated expression of transgenes are an appropriable strategy for effective and stable expression of multi-transgenes. The IRES-based polycistronic transgene vector system also caused sufficient expression of both hCD55 and hCD39. Furthermore, co-transfection of CRISPR/Cas9 and the knock-in vector not only increased the knock-in efficiency but also induced null for GalT by CRISPR/Cas9-mediated double-stranded break of the target site. As shown in human complement-mediated lysis and human antibody binding to GTKO/CD55/CD39 transgenic pig cells, expression of hCD55 and hCD39 with ablation of GalT prevents an effective immunological reaction in vitro. As a consequence, our technique to produce multi-transgenic pigs could improve the development of a suitable xenotransplantation model, and the GTKO/CD55/CD39 pig developed could prolong the survival of pig-to-primate xenotransplant recipients.
2019-04-30 | Generation of GTKO Diannan Miniature Pig Expressing Human Complementary Regulator Proteins hCD55 and hCD59 via T2A Peptide-Based Bicistronic Vectors and SCNT.
Pig-to-human organ transplantation has drawn attention in recent years due to the potential use of pigs as an alternative source of human donor organs. While GGTA1 knockout (GTKO) can protect xenografts from hyperacute rejection, complement-dependent cytotoxicity might still contribute to this type of rejection. To prolong the xenograft survival, we utilized a T2A-mediated pCMV-hCD55-T2A-hCD59-Neo vector and transfected the plasmid into GTKO Diannan miniature pig fetal fibroblasts. After G418 selection combined with single-cell cloning culture, four colonies were obtained, and three of these were successfully transfected with the hCD55 and hCD59. One of the three colonies was selected as donor cells for somatic cell nuclear transfer (SCNT). Then, the reconstructed embryos were transferred into eight recipient gilts, resulting in four pregnancies. Three of the pregnant gilts delivered, yielding six piglets. Only one piglet carried hCD55 and hCD59 genetic modification. The expression levels of the GGTA1, hCD55, and hCD59 in the tissues and fibroblasts of the piglet were determined by q-PCR, fluorescence microscopy, immunohistochemical staining, and western blotting analyses. The results showed the absence of GGTA1 and the coexpression of the hCD55 and hCD59. However, the mRNA expression levels of hCD55 and hCD59 in the GTKO/hCD55/hCD59 pig fibroblasts were lower than that in human 293T cells, which may be caused by low copy number and/or CMV promoter methylation. Furthermore, we performed human complement-mediated cytolysis assays using human serum solutions from 0 to 60%. The result showed that the fibroblasts of this triple-gene modified piglet had greater survival rates than that of wild-type and GTKO controls. Taken together, these results indicate that T2A-mediated polycistronic vector system combined with SCNT can effectively generate multiplex genetically modified pigs, additional hCD55 and hCD59 expression on top of a GTKO genetic background markedly enhance the protective effect towards human serum-mediated cytolysis than those of GTKO alone. Thus, we suggest that GTKO/hCD55/hCD59 triple-gene-modified Diannan miniature pig will be a more eligible donor for xenotransplantation.
2015-04-28 | Adeno-associated virus mediated delivery of an engineered protein that combines the complement inhibitory properties of CD46, CD55 and CD59
Background A variety of disorders are associated with the activation of complement. CD46, CD55 and CD59 are the major membrane associated regulators of complement on human cells. Previously, we have found that independent expression of CD55, CD46 or CD59 through gene transfer protects murine tissues against human complement mediated attack. In the present study, we investigated the potential of combining the complement regulatory properties of CD46, CD55 and CD59 into single gene products expressed from an adeno-associated virus (AAV) vector in a soluble non-membrane anchored form. Methods Minigenes encoding the complement regulatory domains from CD46, CD55 and CD59 (SACT) or CD55 and CD59 (DTAC) were cloned into an AAV vector. The specific regulatory activity of each component of SACT and DTAC was measured in vitro. The recombinant AAV vectors were injected into the peritoneum of mice and the efficacy of the transgene products for being able to protect murine liver vasculature against human complement, specifically the membrane attack complex (MAC), was measured. Results SACT and DTAC exhibited properties similar to CD46, CD55 and CD59 or CD55 and CD59, respectively, in vitro. AAV mediated delivery of SACT or DTAC protected murine liver vasculature from human MAC deposition by 63.2% and 56.7%, respectively. Conclusions When delivered to mice in vivo via an AAV vector, SACT and DTAC are capable of limiting human complement mediated damage. SACT and DTAC merit further study as potential therapies for complement mediated disorders when delivered via a gene therapy approach. Copyright © 2015 John Wiley & Sons, Ltd.
2012-05-11 | Human CD55 expression blocks hyperacute rejection and restricts complement activation in Gal knockout cardiac xenografts.
Transgenic expression of human complement regulatory proteins reduces the frequency of hyperacute rejection (HAR) in Gal-positive cardiac xenotransplantation. In this study, we examined the impact of human CD55 (hCD55) expression on a Gal knockout (GTKO) background using pig-to-primate heterotopic cardiac xenotransplantation. Cardiac xenotransplantation was performed with GTKO (group 1; n=6) and GTKO.hCD55 (group 2; n=5) donor pigs using similar immunosuppression. Cardiac biopsies were obtained 30 min after organ reperfusion. Rejection was characterized by histology and immunohistology. Intragraft gene expression, serum non-Gal antibody, and antibody recovered from rejected hearts were analyzed. HAR of a GTKO heart was observed. Remaining grafts developed delayed xenograft rejection. Median survival was 21 and 28 days for groups 1 and 2, respectively. Vascular antibody deposition was uniformly detected 30 min after organ reperfusion and at explant. A higher frequency of vascular C5b deposition was seen in GTKO organs at explant. Serum non-Gal antibody, antibody recovered from the graft, and intragraft gene expression were similar between the groups. HAR of GTKO hearts without hCD55 may occur. Expression of hCD55 seemed to restrict local complement activation but did not improve graft survival. Chronic vascular antibody deposition with evidence of protracted endothelial cell activation was seen. These observations suggest that non-Gal antibody-induced chronic endothelial cell activation coupled to possible hemostatic incompatibilities may be the primary stimulus for delayed xenograft rejection of GTKO hearts. To avoid possible HAR, future clinical studies should use donors expressing human complement regulatory proteins in the GTKO background.
2010-11-02 | Adenovirus capsid-display of the retro-oriented human complement inhibitor DAF reduces Ad vector-triggered immune responses in vitro and in vivo.
Adenovirus (Ad) vectors are widely used in human clinical trials. However, at higher dosages, Ad vector-triggered innate toxicities remain a major obstacle to many applications. Ad interactions with the complement system significantly contribute to innate immune responses in several models of Ad-mediated gene transfer. We constructed a novel class of Ad vectors, genetically engineered to "capsid-display" native and retro-oriented versions of the human complement inhibitor decay-accelerating factor (DAF), as a fusion protein from the C-terminus of the Ad capsid protein IX. In contrast to conventional Ad vectors, DAF-displaying Ads dramatically minimized complement activation in vitro and complement-dependent immune responses in vivo. DAF-displaying Ads did not trigger thrombocytopenia, minimized endothelial cell activation, and had diminished inductions of proinflammatory cytokine and chemokine responses. The retro-oriented display of DAF facilitated the greatest improvements in vivo, with diminished activation of innate immune cells, such as dendritic and natural killer cells. In conclusion, Ad vectors can capsid-display proteins in a manner that not only retains the functionality of the displayed proteins but also potentially can be harnessed to improve the efficacy of this important gene transfer platform for numerous gene transfer applications.
proteins
2023-10-25 | The monosialoganglioside GM1a protects against complement attack
The complement system is a part of the innate immune system in the fluid phase and efficiently eliminates pathogens. However, its activation requires tight regulation on the host cell surface in order not to compromise cellular viability. Previously, we showed that loss of placental cell surface sialylation in mice in vivo leads to a maternal complement attack at the fetal-maternal interface, ultimately resulting in loss of pregnancy. To gain insight into the regulatory function of sialylation in complement activation, we here generated trophoblast stem cells (TSC) devoid of sialylation, which also revealed complement sensitivity and cell death in vitro. Glycolipid-analysis by multiplexed capillary gel electrophoresis coupled to laser-induced fluorescence detection (xCGE-LIF) allowed us to identify the monosialoganglioside GM1a as a key element of cell surface complement regulation. Exogenously administered GM1a integrated into the plasma membrane of trophoblasts, substantially increased binding of complement factor H (FH) and was sufficient to protect the cells from complement attack and cell death. GM1a treatment also rescued human endothelial cells and erythrocytes from complement attack in a concentration dependent manner. Furthermore, GM1a significantly reduced complement mediated hemolysis of erythrocytes from a patient with Paroxysmal nocturnal hemoglobinuria (PNH). This study demonstrates the complement regulatory potential of exogenously administered gangliosides and paves the way for sialoglycotherapeutics as a novel substance class for membrane-targeted complement regulators.
2022-01-10 | Hemopexin Modulates Expression of Complement Regulatory Proteins in Rat Glomeruli.
In systemic hemolysis and in hematuric forms of kidney injury, the major heme scavenging protein, hemopexin (HPX), becomes depleted, and the glomerular microvasculature (glomeruli) is exposed to high concentrations of unbound heme, which, in addition to causing oxidative injury, can activate complement cascades; thus, compounding extent of injury. It is unknown whether unbound heme can also activate specific complement regulatory proteins that could defend against complement-dependent injury. Isolated rat glomeruli were incubated in media supplemented with HPX-deficient (HPX-) or HPX-containing (HPX+) sera as a means of achieving different degrees of heme partitioning between incubation media and glomerular cells. Expression of heme oxygenase (HO)-1 and of the complement activation inhibitors, decay-accelerating factor (DAF), CD59, and complement receptor-related gene Y (Crry), was assessed by western blot analysis. Expression of HO-1 and of the GPI-anchored DAF and CD59 proteins increased in isolated glomeruli incubated with HPX- sera with no effect on Crry expression. Exogenous heme (hemin) did not further induce DAF but increased Crry expression. HPX modulates heme-mediated induction of complement activation controllers in glomeruli. This effect could be of translational relevance in glomerular injury associated with hematuria.
2019-08-30 | Combining MAP‐1:CD35 or MAP‐1:CD55 fusion proteins with pattern‐recognition molecules as novel targeted modulators of the complement cascade
Dysregulation of the complement system is involved in the pathogenesis of several diseases, and its inhibition has been shown to be a feasible therapeutic option. Therefore, there is an interest in the development of complement modulators to treat complement activation-related inflammatory pathologies. Mannose-binding lectin (MBL)/ficolin/collectin-associated protein-1 (MAP-1) is a regulatory molecule of the lectin pathway (LP), whereas complement receptor 1 (CD35) and decay-accelerating factor (CD55) are membrane-anchored regulators with effects on the central effector molecule C3. In this study, we developed 2 novel soluble chimeric inhibitors by fusing MAP-1 to the 3 first domains of CD35 (CD351-3) or the 4 domains of CD55 (CD551-4) to modulate the complement cascade at 2 different stages. The constructs showed biologic properties similar to those of the parent molecules. In functional complement activation assays, the constructs were very efficient in inhibiting LP activation at the level of C3 and in the formation of terminal complement complex. This activity was enhanced when coincubated with recombinant LP recognition molecules MBL and ficolin-3. Recombinant MAP-1 fusion proteins, combined with recombinant LP recognition molecules to target sites of inflammation, represent a novel and effective therapeutic approach involving the initiation and the central and terminal effector functions of the complement cascade.-Pérez-Alós, L., Bayarri-Olmos, R., Skjoedt, M.-O., Garred, P. Combining MAP-1:CD35 or MAP-1:CD55 fusion proteins with pattern-recognition molecules as novel targeted modulators of the complement cascade.
2017-05-13 | Overexpression of Human CD55 and CD59 or Treatment with Human CD55 Protects against Renal Ischemia-Reperfusion Injury in Mice
Abstract Deficiency in the membrane-bound complement regulators CD55 and CD59 exacerbates renal ischemia-reperfusion injury (IRI) in mouse models, but the effect of increasing CD55 and CD59 activity has not been examined. In this study, we investigated the impact of overexpression of human (h) CD55 ± hCD59 or treatment with soluble rhCD55 in a mouse model of renal IRI. Unilaterally nephrectomised mice were subjected to 18 (mild IRI) or 22 min (moderate IRI) warm renal ischemia, and analyzed 24 h after reperfusion for renal function (serum creatinine and urea), complement deposition (C3b/c and C9), and infiltration of neutrophils and macrophages. Transgenic mice expressing hCD55 alone were protected against mild renal IRI, with reduced creatinine and urea levels compared with wild type littermates. However, the renal function of the hCD55 mice was not preserved in the moderate IRI model, despite a reduction in C3b/c and C9 deposition and innate cell infiltration. Mice expressing both hCD55 and hCD59, on the other hand, were protected in the moderate IRI model, with significant reductions in all parameters measured. Wild type mice treated with rhCD55 immediately after reperfusion were also protected in the moderate IRI model. Thus, manipulation of CD55 activity to increase inhibition of the C3 and C5 convertases is protective against renal IRI, and the additional expression of hCD59, which regulates the terminal complement pathway, provides further protection. Therefore, anti-complement therapy using complement regulatory proteins may provide a potential clinical option for preventing tissue and organ damage in renal IRI.
2014-08-11 | A novel CRIg‐targeted complement inhibitor protects cells from complement damage
The inappropriate activation of complement may contribute to various immune diseases. The alternative pathway (AP) predominates during complement activation regardless of the initiating pathways. Hence, the main AP regulator factor H (FH) holds great potential as an attractive therapeutic intervention. In addition, complement receptor of the immunoglobulin superfamily (CRIg) has been demonstrated to inhibit AP and, more notably, still specifically binds to C3b/iC3b. We thus developed novel CRIg-targeted complement inhibitors by connecting the functional domains of CRIg and FH, which we termed CRIg-FH and CRIg-L-FH. CRIg-L-FH, slightly more potent than CRIg-FH, considerably inhibited both AP- and also classical pathway (CP)-mediated hemolysis and successfully eliminated the deposition of C3b/iC3b. Kinetic analysis further revealed that the binding affinity constant (KD) of CRIg/FH was in the micromolar range, consistent with its long-lasting binding to complement-attacked cells. CRIg-L-FH efficiently protected aberrant erythrocytes of patients with paroxysmal nocturnal hemoglobinuria (PNH) from AP-and CP-mediated complement damage (IC50 was 22.43 and 64.69 nM, respectively). Moreover, CRIg-L-FH was found to inhibit complement activation induced by the anti-Thy1 antibody in a mesangiopro-liferative glomerulonephritis (MPGN) rat model. Hence, CRIg-L-FH protects glomerular mesangial cells (GMCs) from complement-mediated injury and proliferative lesions. These findings strongly suggest that CRIg/FH is a potential therapeutic drug candidate for a range of complement-mediated diseases.—Qiao, Q., Teng, X., Wang, N., Lu, R., Guo, L., Zhang, X., Du, Y., Wang, W., Chen, S., Wu, Q., He, G., Wang, Y., and Hu, W., A novel CRIg-targeted complement inhibitor protects cells from complement damage. FASEB J. 28, 4986–4999 (2014). www.fasebj.org
small molecules
2023-03-10 | SAR443809: a selective inhibitor of the complement alternative pathway, targeting complement factor Bb
Dysregulated activation of the complement system is implicated in the onset or progression of several diseases. Most clinical-stage complement inhibitors target the inactive complement proteins present at high concentrations in plasma, which increases target-mediated drug disposition and necessitates high drug levels to sustain therapeutic inhibition. Furthermore, many efforts are aimed at inhibiting only terminal pathway activity, which leaves opsonin-mediated effector functions intact. We describe the discovery of SAR443809, a specific inhibitor of the alternative pathway C3/C5 convertase (C3bBb). SAR443809 selectively binds to the activated form of factor B (factor Bb) and inhibits alternative pathway activity by blocking the cleavage of C3, leaving the initiation of classical and lectin complement pathways unaffected. Ex vivo experiments with patient-derived paroxysmal nocturnal hemoglobinuria erythrocytes show that, although terminal pathway inhibition via C5 blockade can effectively inhibit hemolysis, proximal complement inhibition with SAR443809 inhibits both hemolysis and C3b deposition, abrogating the propensity for extravascular hemolysis. Finally, intravenous and subcutaneous administration of the antibody in nonhuman primates demonstrated sustained inhibition of complement activity for several weeks after injection. Overall, SAR443809 shows strong potential for treatment of alternative pathway-mediated disorders.
2022-04-19 | Mathematical Modeling of Complement Pathway Dynamics for Target Validation and Selection of Drug Modalities for Complement Therapies
Motivation: The complement pathway plays a critical role in innate immune defense against infections. Dysregulation between activation and regulation of the complement pathway is widely known to contribute to several diseases. Nevertheless, very few drugs that target complement proteins have made it to the final regulatory approval because of factors such as high concentrations and dosing requirements for complement proteins and serious side effects from complement inhibition. Methods: A quantitative systems pharmacology (QSP) model of the complement pathway has been developed to evaluate potential drug targets to inhibit complement activation in autoimmune diseases. The model describes complement activation via the alternative and terminal pathways as well as the dynamics of several regulatory proteins. The QSP model has been used to evaluate the effect of inhibiting complement targets on reducing pathway activation caused by deficiency in factor H and CD59. The model also informed the feasibility of developing small-molecule or large-molecule antibody drugs by predicting the drug dosing and affinity requirements for potential complement targets. Results: Inhibition of several complement proteins was predicted to lead to a significant reduction in complement activation and cell lysis. The complement proteins that are present in very high concentrations or have high turnover rates (C3, factor B, factor D, and C6) were predicted to be challenging to engage with feasible doses of large-molecule antibody compounds (≤20 mg/kg). Alternatively, complement fragments that have a short half-life (C3b, C3bB, and C3bBb) were predicted to be challenging or infeasible to engage with small-molecule compounds because of high drug affinity requirements (>1 nM) for the inhibition of downstream processes. The drug affinity requirements for disease severity reduction were predicted to differ more than one to two orders of magnitude than affinities needed for the conventional 90% target engagement (TE) for several proteins. Thus, the QSP model analyses indicate the importance for accounting for TE requirements for achieving reduction in disease severity endpoints during the lead optimization stage.
2019-04-04 | Polyphosphates and Complement Activation
To sustain life in environments that are fraught with risks of life-threatening injury, organisms have developed innate protective strategies such that the response to wounds is rapid and localized, with the simultaneous recruitment of molecular, biochemical and cellular pathways that limit bleeding and eliminate pathogens and damaged host cells, while promoting effective healing. These pathways are tightly regulated, as their over- or under-activation may lead to inadequate healing, disease, and/or demise of the host. Recent advances in our understanding of coagulation and complement, a key component of innate immunity, have revealed critical molecular links that regulate the delicate balance of both systems, thereby providing the necessary elements to achieve homeostasis. Polyphosphate is one such factor that intriguingly, plays a key role by promoting coagulation, while dampening complement activation, a discovery that is uncovering novel insights into mechanisms underlying disease and new therapeutic strategies.
2017-08-16 | Heme Oxygenase 1 Up-Regulates Glomerular Decay Accelerating Factor Expression and Minimizes Complement Deposition and Injury.
Complement-activation controllers, including decay accelerating factor (DAF), are gaining emphasis as they minimize injury in various dysregulated complement-activation disorders, including glomerulopathies. Heme oxygenase (HO)-1 overexpression or induction has been shown to attenuate injury in complement-dependent models of glomerulonephritis. This study investigated whether up-regulation of DAF by heme oxygenase 1 (HO-1) is an underlying mechanism by using Hmox-1-deficient rats (Hmox1+/-; Hmox1-/-) or rats with HO-1 overexpression targeted to glomerular epithelial cells (GECHO-1), which are particularly vulnerable to complement-mediated injury owing to their terminally differentiated nature. Constitutively expressed DAF was decreased in glomeruli of Hmox1-/- rats and augmented in glomeruli of GECHO-1 rats. In GECHO-1 rats with anti-glomerular basement membrane antibody mediated, complement-dependent injury, complement component C3 fragment b (C3b) deposition was reduced, whereas proteinuria was diminished. In glomeruli of wild-type rats, the natural Hmox substrate, hemin, induced glomerular DAF. This effect was attenuated in glomeruli of Hmox1-/- rats and augmented in glomeruli of GECHO-1 rats. Hemin analogues differing in either metal or porphyrin ring functionalities, acting as competitive Hmox-substrate inhibitors, also increased glomerular DAF and reduced C3b deposition after spontaneous complement activation. In the presence of a DAF-blocking antibody, the reduction in C3b deposition was reversed. These observations establish HO-1 as a physiologic regulator of glomerular DAF and identify hemin analogues as inducers of functional glomerular DAF able to minimize C3b deposition.
2017-02-10 | Complement’s hidden arsenal: New insights and novel functions inside the cell
A key component of both innate and adaptive immunity, new understandings of the complement system are expanding its roles beyond that traditionally appreciated. Evidence is accumulating that complement has an intracellular arsenal of components that provide not only immune defense, but also assist in key interactions for host cell functions. Although early work has primarily centered on T cells, the intracellular complement system likely functions in many if not most cells of the body. Some of these functions may trace their origins to the primitive complement system that began as a primeval form of C3 likely tasked for protection from intracellular pathogen invasion. This later expanded to include extracellular defense as C3 became a secreted protein to patrol the vasculature. Other components were added to the growing system including regulators to protect host cells from the indiscriminate effects of this potent system. Contemporary cells may retain some of these vestigial remnants. We now know that a) C3 serves as a damage-associated molecular pattern (in particular by coating pathogens that translocate into cells), b) most cells store C3 and recycle C3(H2O) for immediate use, and c) C3 assists in cellular survival and metabolic reprogramming. Other components also are part of this hidden arsenal including C5, properdin, factors H and B, and complement receptors. Importantly, better definition of the intracellular complement system may translate into new target discovery to assist in creating the next generation of complement therapeutics.
antibodies
2026-08-17 | Targeted complement inhibition with pozelimab in children with CD55 deficiency.
CHAPLE syndrome is an ultra-rare genetic cause of protein-losing enteropathy (PLE) resulting from uncontrolled complement activation due to CD55 deficiency. We report two paediatric patients presenting with recurrent diarrhoea, hypoalbuminaemia, hypogammaglobulinaemia and growth failure, both initially evaluated as intestinal lymphangiectasia. Persistent symptoms and poor response to conventional therapy prompted genetic evaluation, which revealed pathogenic variants in the CD55 gene in both children, confirming the diagnosis of CHAPLE syndrome. Both patients required repeated albumin and intravenous immunoglobulin replacement prior to diagnosis. Targeted therapy with pozelimab was initiated. Rapid clinical and biochemical improvement was observed within 2 weeks, with sustained normalisation of albumin, total protein and immunoglobulin levels. At 3-month follow-up, both children remained in clinical remission without further need for albumin or immunoglobulin infusions. These cases highlight the importance of considering genetic causes in children with refractory PLE and demonstrate the effectiveness of early targeted complement inhibition in CHAPLE syndrome.
2026-05-28 | C5 inhibition restores B cell homeostasis and humoral immunity in CHAPLE disease patients.
CHAPLE disease is a monogenic disorder in which CD55 deficiency drives gastrointestinal pathology. How CD55 deficiency affects adaptive immunity is unknown. Herein, molecularly, we characterize eight patients with genetically novel CD55 deficiency. Clinically, all patients developed early-onset protein-losing enteropathy, frequently complicated by thrombotic events, inflammatory bowel disease-like lesions, and recurrent respiratory infections. Ex vivo, immunophenotyping revealed disruption of the B cell compartment, marked by depletion of transitional B cells, expansion of CD21lo B cells, and accumulation of class-switched memory B cells and plasmablasts, while T cell subsets were largely preserved. In vivo, eculizumab rapidly resolved intestinal pathology, normalized serum albumin and immunoglobulin levels, and re-established a normal B cell profile. Furthermore, C5 inhibition enabled effective humoral protection and optimal pneumococcal vaccine responses. Together, these findings establish complement inhibition as central to B cell homeostasis in CHAPLE disease.
2026-04-01 | P15 When N <100: compassionate use of a novel therapy in CHAPLE syndrome
C H A P L E syndrome (CD55 deficiency) is an ultra-rare primary immunodeficiency, with fewer than 100 cases reported globally. 1 A paediatric patient at a tertiary paediatric centre in the United Kingdom was granted compassionate access to pozelimab, a novel monoclonal antibody imported from the United States. Delivering this treatment required close multidisciplinary collaboration between the consultant immunologist, specialist nurse, and pharmacy teams, including clinical, quality assurance, and procurement.The pharmacy team ensured the clinical appropriateness of the treatment through independent evaluation of the patient’s condition and the available evidence. In the absence of established protocols or reference sources, they implemented clinical governance measures to support safe prescribing and administration, including documentation, dosing guidance, and risk mitigation strategies. Pharmacists played an active role in patient and family engagement, providing education and counselling to support informed decision-making. In parallel, the pharmacy team also managed regulatory liaison, importation, and arrangements for continued supply.An online meeting was held with the patient and parent to explore their perspectives on the compassionate use process. The patient, who had previously received immunosuppressants including biologics, expressed relief at finally having a confirmed diagnosis and a treatment specifically targeting her condition. Although initially concerned about side effects, she understood the associated risks from prior experience and felt reassured. She preferred receiving verbal information from the consultant, nurse, and pharmacist but felt written material would be helpful for future reference. She was surprised that the medication came in a vial rather than a prefilled pen or syringe but ultimately preferred the vial and appreciated the team’s efforts to explore pain-minimising techniques that worked for her.The parent also expressed relief at the diagnosis, but noted difficulty accessing peer support or patient experiences due to the rarity of the condition. Despite receiving written materials and links to the manufacturer’s website, she felt reading about others’ experiences would have offered greater reassurance when deciding to start treatment. She highly praised the multidisciplinary approach and the effectiveness of communication across the team. The pharmacist’s presence during the first administration was particularly valued, though she suggested earlier pharmacy involvement—ideally when the drug was first proposed in clinic—would have been beneficial. She also identified a need for more lifestyle and dietary guidance to support ongoing care. Overall, both parent and patient felt supported in their decision to begin treatment and expressed high satisfaction with the pharmacy team’s contribution and the collaborative approach.Conclusion Delivering compassionate use treatment for ultra-rare diseases requires coordinated, multidisciplinary care. The input of the consultant, nurse, and pharmacy teams was central to supporting the family and ensuring treatment was initiated safely. This case highlights the importance of early pharmacy involvement, structured governance processes, and person-centred communication. Patient and parent feedback reinforced the value of accessible information and the reassurance provided by collaborative, transparent care in the context of rare disease management.Reference Litcher-Kelly L, Ozen A, Ollis S, et al. The patient experience of CHAPLE disease: results from interviews conducted as part of a clinical trial for an ultra-rare condition. Orphanet Journal of Rare Diseases 2025;20:68.
2026-03-24 | Evaluating pozelimab in the treatment of CHAPLE disease.
CHAPLE disease (Complement Hyperactivation, Angiopathic Thrombosis, and Protein-Losing Enteropathy [PLE]) is a rare, life-threatening disorder caused by biallelic mutations in the CD55 gene, which encodes decay-accelerating factor, a key regulator of the complement system. The disease typically manifests in early childhood with hypoalbuminemic edema, gastrointestinal symptoms, recurrent infections, and failure to thrive, alongside an elevated thrombotic risk due to complement-mediated endothelial injury and coagulation activation. Given these pathogenetic mechanisms, complement-targeted therapies have emerged as a rational approach to disease management. Eculizumab, a monoclonal antibody against complement component C5, initially demonstrated clinical benefit when administered on a compassionate-use basis. Building upon this success, pozelimab, a next-generation subcutaneous anti-C5 monoclonal antibody, was evaluated in CHAPLE patients and subsequently received U.S. FDA approval for this indication. Pozelimab effectively inhibits terminal complement activation, leading to sustained remission of PLE, obviating the need for albumin replacement, reducing hospitalization rates, improving symptom control and nutritional status, and ultimately enhancing overall quality of life. This review highlights the evolving role of pozelimab in CHAPLE disease by discussing its mechanistic basis, emerging clinical evidence, and implications for patient-centered care.
2025-11-22 | The Critical Role of Biochemical and Genetic Diagnosis in Differentiating CHAPLE Syndrome from Treatment-Resistant IBD: A Case Study
Background: CHAPLE syndrome (Complement Hyperactivation, Angiopathic Thrombosis, and Protein-Losing Enteropathy) is an extremely rare and life-threatening monogenic disease caused by loss-of-function mutations of CD55 leading to dysregulation of the alternative complement pathway. The clinical pattern characterized by PLE and chronic inflammatory disease is frequently misattributed to idiopathic bowel disease (IBD) with consequent inappropriate and prolonged treatment with immunosuppressive drugs. Methods: We report on a 6-year-old boy with early-onset chronic diarrhea, failure to thrive and steroid-dependent PLE that was initially identified as IBD. To resolve the diagnostic confusion, a fulminant biochemical and genetic lookups were performed. Results: This patient's sustained biochemical abnormalities severe hypoalbuminemia (15-22 g/L), profound thrombocytosis (platelets> 800 x 10⁹/l) and dimorphic anaemia were unrelated to traditional IBD. Genetic central sequencing demonstrated a homozygous deleterious CD55 variant, confirming the diagnosis of CHAPLE syndrome. This diagnosis provided the pathophysiological explanation for complement activation. Discussion: Treatment was consequently changed from corticosteroids to pozelimab, a complement C5 inhibitor monoclonal antibody. This therapy resulted in a prompt normalization of serum albumin and relief from gastrointestinal symptoms with subsequent prolonged clinical remission. Conclusions: We report a case, which highlights that a particular combination of biochemical aberrations in a previously well individual with refractory IBD should bring to mind monogenic causes including CHAPLE syndrome. Genetic testing is the best and most accurate way to diagnose a disorder. It is a revolution in the treatment of disease: away from nonspecific suppression of the immune system and toward targeted biologic therapy aimed at its precise cause — with dramatically better outcomes. Identification of these patterns and advising on confirmatory testing is a responsibility of clinical biochemists.
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Drug Discovery Landscape
1 orphan drug designation for Complement hyperactivation-angiopathic thrombosis-protein-losing enteropathy syndrome, including 1 approved therapy.
1 orphan drug designation for Complement hyperactivation-angiopathic thrombosis-protein-losing enteropathy syndrome, including 1 approved therapy.
Drug | Therapy type | Regulator | Orphan designation | Approval | Sponsor |
|---|---|---|---|---|---|
pozelimab-bbfg [Veopoz] | antibodies | FDA | 2020-04-13 | 2023-08-18 | Regeneron Pharmaceuticals, Inc. |
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