Inhibition of complement activity by humanized anti-C5 antibody and single-chain Fv

A review of the use of biological agents for chronic inflammatory demyelinating polyradiculoneuropathy

Chronic inflammatory demyelinating polyneuropathy (CIDP) is a group of idiopathic, acquired, immune-mediated inflammatory demyelinating diseases of the peripheral nervous system. A majority of patients with CIDP respond to "first-line" treatment with IVIG, plasmapheresis and/or corticosteroids. There exists insufficient evidence to ascertain the benefit of treatment with "conventional" immunosuppressive drugs. The inconsistent efficacy, long-term financial burden and health risks of non-specific immune altering therapy have drawn recurrent attention to the possible usefulness of a variety of biological agents that target key aspects in the CIDP immunopathogenic pathways. This review aims to give an updated account of the scientific rationale and potential use of biological therapeutics in patients with CIDP. No specific treatment recommendations are given. The discovery, development and application of biological markers by modern molecular diagnostic techniques may help identify drug-naïve or treatment-resistant CIDP patients most likely to respond to targeted immunotherapy.

Humoral-targeted immunotherapies in multiple sclerosis

The continuous improvements of our understanding of the pathophysiological changes that occur in multiple sclerosis (MS) have translated into many novel therapeutic agents at different stages of development. These agents target more specifically the innate or the adaptive immune response. We will review agents available or under development that target the humoral pathways of the adaptive immune response. As such, humoral targeted immunotherapies that are being developed for MS are discussed herein: rituximab, ocrelizumab, and ofatumumab show promise as B-cell depleting agents. Other agents, such as atacicept were suspended during development in MS due to increased inflammatory activity versus the placebo. Although most agents were tested in relapsing-remitting forms of MS, rituximab and ocrelizumab have both been studied in progressive MS, whereas ocrelizumab only is currently moving forward in primary progressive MS trials. We provide an overview of agents available and under development that target the humoral response and include their mechanisms of action, safety profiles, and results of clinical trials.

Monitoring and modeling treatment of atypical hemolytic uremic syndrome

Atypical hemolytic uremic syndrome (aHUS), is mainly present in children, who have high risks of end-stage kidney disease (ESKD), post-transplant recurrence and death. aHUS is linked to defective regulation of the complement alternative pathway (AP), with a prominent cause being mutation/inhibition of the negative regulator complement factor H (CFH). CFH function can be restored via infusion of fresh frozen plasma (FFP), a treatment that was effective for several years in a patient heterozygous for a cfh mutation, before the patient progressed to ESKD. While on dialysis, FFP was replaced with eculizumab, which blocks C5 cleavage and thus halts progression of the terminal complement pathway. Patient plasma samples collected during FFP and eculizumab treatment phases were assessed for AP activity (via erythrocyte lysis assays) and for overall complement activity (via ELISA-based screen). Assay results indicated that FFP partially restored AP regulation, an observation supported by in vitro modeling of FFP treatment using purified CFH, while eculizumab completely blocked complement activity. The same approach was used to model in vitro a potential aHUS treatment approach based on blocking the AP effector properdin (complement factor P; CFP) with an anti-properdin antibody. These results provide insights into the efficacy of aHUS treatment and highlight the usefulness of in vitro assays in monitoring and predicting therapeutic responses and testing new treatment possibilities.

Prevention of antibody-mediated kidney transplant rejection

There is increasing evidence that antibody-mediated rejection is the major cause of late kidney graft failure. Prevention of antibody-mediated allograft damage has therefore become an important issue in kidney transplantation. Such prevention starts already before transplantation with the avoidance of sensitizing events. When a patient is already sensitized, precise characterization of alloantibodies and exact HLA typing of the donor at the time of transplantation are mandatory. To ensure timely and successful transplantation of highly sensitized patients, desensitization, and inclusion in special programs such as the Eurotransplant Acceptable Mismatch Program should be considered. After transplantation, close monitoring of kidney function, testing for the de novo development or changing characteristics of alloantibodies, and attention to non-adherence to immunosuppression is obligatory. In the current overview, we discuss the currently available measures for the prevention of antibody-mediated kidney graft rejection.

Paroxysmal nocturnal hemoglobinuria in pediatric patients

BACKGROUND

Paroxysmal nocturnal hemoglobinuria (PNH) is a rare disease in children. The most significant clinical features of PNH include: bone marrow failure, intravascular hemolysis, and thrombosis. To further characterize the clinical presentation and outcome to treatment we performed a retrospective analysis of pediatric patients with PNH.

PROCEDURE

We reviewed the medical records of 12 consecutive pediatric patients with PNH diagnosed at our institution from 1992 to 2010.

RESULTS

Presenting clinical symptoms included: bone marrow failure (N = 10); gross hemoglobinuria with isolated red cell anemia (N = 1); and jaundice, hepatitis, and isolated thrombocytopenia (N = 1). Immunosuppressive therapy was the initial treatment for 8 patients. Five patients had myelodysplastic features without developing excessive blasts or leukemic transformation. Thrombosis occurred in 6 patients. Five patients underwent hematopoietic stem cell transplant (HSCT) of whom 3 patients are alive and disease-free. Three patients received anti-complement therapy with eculizumab. Two patients died following complications related to thrombosis and 2 patients are transfusion independent with stable disease.

CONCLUSION

This report highlights a high rate of bone marrow failure along with a low rate of hemoglobinuria at presentation, a high rate of thrombosis, and for some patients the spontaneous resolution of myelodysplastic features. Delay in diagnosis is common and we recommend appropriate PNH testing in all patients with AA, MDS, unexplained Coombs-negative hemolysis, or thrombosis. While HSCT remains the only curative option the high prevalence of hemolysis and thrombosis should warrant the consideration of early treatment with anti-complement therapy.

Chemical Biology, Molecular Mechanism and Clinical Perspective of γ-Secretase Modulators in Alzheimer's Disease

Comprehensive evidence supports that oligomerization and accumulation of amyloidogenic Aβ42 peptides in brain is crucial in the pathogenesis of both familial and sporadic forms of Alzheimer's disease. Imaging studies indicate that the buildup of Aβ begins many years before the onset of clinical symptoms, and that subsequent neurodegeneration and cognitive decline may proceed independently of Aβ. This implies the necessity for early intervention in cognitively normal individuals with therapeutic strategies that prioritize safety. The aspartyl protease γ-secretase catalyses the last step in the cellular generation of Aβ42 peptides, and is a principal target for anti-amyloidogenic intervention strategies. Due to the essential role of γ-secretase in the NOTCH signaling pathway, overt mechanism-based toxicity has been observed with the first generation of γ-secretase inhibitors, and safety of this approach has been questioned. However, two new classes of small molecules, γ-secretase modulators (GSMs) and NOTCH-sparing γ-secretase inhibitors, have revitalized γ-secretase as a drug target in AD. GSMs are small molecules that cause a product shift from Aβ42 towards shorter and less toxic Ab peptides. Importantly, GSMs spare other physiologically important substrates of the γ-secretase complex like NOTCH. Recently, GSMs with nanomolar potency and favorable in vivo properties have been described. In this review, we summarize the knowledge about the unusual proteolytic activity of γ-secretase, and the chemical biology, molecular mechanisms and clinical perspective of compounds that target the γ-secretase complex, with a particular focus on GSMs.

Complement activation and cardiac surgery: a novel target for improving outcomes

Complement activation and the resulting inflammatory response is an important potential mechanism for multisystem organ injury in cardiac surgery. Novel therapeutic strategies using complement inhibitors may hold promise for improving outcomes for cardiac surgical patients by attenuating complement activation or its biologically active effector molecules. Recent clinical trials evaluating complement inhibitors have provided important data to further delineate the impact of complement activation and its inhibition on clinical outcomes. In this review we examine the role of complement activation and its inhibition as a therapeutic approach in cardiac surgery.

Pexelizumab fails to inhibit assembly of the terminal complement complex in patients with ST-elevation myocardial infarction undergoing primary percutaneous coronary intervention. Insight from a substudy of the Assessment of Pexelizumab in Acute Myocardial Infarction (APEX-AMI) trial

BACKGROUND

Reasons for pexelizumab lack of benefit in ST-elevation myocardial infarction patients undergoing primary percutaneous coronary intervention remain unclear. In a substudy of the APEX-AMI trial, we explored the hypothesis that early complement activation preceding drug administration explained the failure.

METHODS

A panel of terminal complement complex proteins and fragments and biomarkers of inflammation, apoptosis, and high-risk features were assessed in serum obtained before and 24 hours after administration of placebo or pexelizumab and primary percutaneous coronary intervention (n = 356) and in human umbilical vein endothelial cell cultures coincubated with serum (n = 45).

RESULTS

In the placebo group, C5a and sC5b-9 levels increased by 37% (7.9-14.2 ηg/mL, P = .007) and 96% (442-845 ηg/mL, P < .0001), respectively, during the first 24 hours. Pexelizumab prevented the increase in C5a (P = .01 vs placebo), but not that of sC5b-9 (502-1,157 ηg/mL, not significant vs placebo). Levels of C-reactive protein, interleukin (IL) 6, IL-1ß, Regulated on Activation, Normal T Cell Expressed and Secreted (RANTES) or Chemokine C-C motif ligand 5 (CCL5), and N-terminal probrain natriuretic peptide increased significantly in both groups; those of IL-10, IL-12, IL-1ra, and Interferon gamma-induced protein 10 (IP-10) or C-X-C motif chemokine 10 (CXCL10) decreased. Pexelizumab halved the increase in IL-6 (+92% vs 156%, P = .01) without effects on other markers, including C-reactive protein and N-terminal probrain natriuretic peptide. In cell culture, pexelizumab inhibited C5a, sC5b-9, and membrane-bound C5b-9 by 92%, 75%, and 78%, respectively (all P < .0001), without influencing cytokine levels and cell apoptosis.

CONCLUSIONS

The blockage of both C5a and terminal complement in cell culture, but of C5a only in vivo with minimal effects on inflammation and risk biomarkers, supports the hypothesis that late administration of pexelizumab after the ischemia/reperfusion insult precluded adequate myocardial protection, resulting in a negative trial.

Pathology after eculizumab in dense deposit disease and C3 GN

Eculizumab might benefit C3 glomerulopathies mediated by dysregulation of the alternative complement pathway. Here, we report renal biopsy findings before and after eculizumab therapy in three patients with dense deposit disease and two with C3 GN. All pretreatment biopsies had glomerular and tubular basement membrane deposits that stained exclusively for C3 without significant Ig. After 1 year of therapy, there was reduction in active glomerular proliferation and neutrophil infiltration in three of five patients, consistent with effective C5 blockade, which prevents production of chemotactin C5a. One individual with mild mesangial disease had no significant change in activity or chronicity. One patient exhibited persistent activity and worsening chronicity despite therapy. Immunofluorescence showed no significant reduction in C3 or C5b-9, and electron microscopy revealed persistent deposits in all cases, suggesting a long t(1/2) of C5b-9 in extracellular matrix. Normal renal biopsies stained positive for C5b-9 in glomeruli, tubular basement membranes, and vessel walls, albeit at lower intensity than in C3 glomerulopathy. This indication of physiologic levels of C5b-9 activation in normal kidney potentially explains the localization of deposits in patients with dysregulation of the alternative complement pathway. All post-treatment biopsies showed de novo monoclonal staining for IgG-κ in the same distribution as C3 and C5b-9, mimicking monoclonal Ig deposition disease (MIDD). Staining of the γ heavy chain was restricted to the IgG2 and IgG4 subclasses, suggesting the binding of monoclonal eculizumab to C5 in renal tissues. The long-term effects of this apparent drug-tissue interaction are unknown.

A trial of complement inhibition in a patient with cryoglobulin-induced glomerulonephritis

Cryoglobulinemia induces an immune complex-mediated glomerulonephritis that is characterized by the presence of large immune deposits, including complement C3 and C5b-9, marked macrophage influx and mesangial cell proliferation. The precise role of complement in cryoglobulin-induced glomerulonephritis in humans remains unclear, whereas in mice there has been evidence that complement activation might be a central factor favoring glomerular inflammation, particularly by the recruitment of neutrophils. We report on an exceptional case of cryoglobulin-induced glomerulonephritis in a patient with mixed essential cryoglobulinemia type II. The clinical features included relapsing proteinuria and renal function impairment that were controlled by plasmapheresis. Complement was low in plasma and two renal biopsies at 1-year interval showed prominent immunoglobulin and complement deposits, with unusual high numbers of neutrophils. In a 1-patient clinical trial, we tested whether the monoclonal anti-C5 antibody eculizumab would be sufficient to control renal function at the time of a relapse. Although during the initial weeks renal function was stabilized, slow increase in creatinine could not be controlled by this treatment, so that plasmapheresis was reinstituted. This result suggests that despite evidence for a role of complement in enhancing renal damage in this patient, other inflammatory processes dominated.

Fetal and Neonatal Illnesses Caused or Influenced by Maternal Transplacental IgG and/or Therapeutic Antibodies Applied During Pregnancy

The human fetus is protected by the mother’s antibodies. At the end of the pregnancy, the concentration of maternal antibodies is higher in the cord blood, than in the maternal circulation. Simultaneously, the immune system of the fetus begins to work and from the second trimester, fetal IgM is produced by the fetal immune system specific to microorganisms and antigens passing the maternal-fetal barrier. The same time the fetal immune system has to cope and develop tolerance and T_REG cells to the maternal microchimeric cells, latent virus-carrier maternal cells and microorganisms transported through the maternal-fetal barrier.

The maternal phenotypic inheritance may hide risks for the newborn, too. Antibody mediated enhancement results in dengue shock syndrome in the first 8 month of age of the baby.

A series of pathologic maternal antibodies may elicit neonatal illnesses upon birth usually recovering during the first months of the life of the offspring. Certain antibodies, however, may impair the fetal or neonatal tissues or organs resulting prolonged recovery or initiating prolonged pathological processes of the children.

The importance of maternal anti-idiotypic antibodies are believed to prime the fetal immune system with epitopes of etiologic agents infected the mother during her whole life before pregnancy and delivery.

The chemotherapeutical and biological substances used for the therapy of the mother will be transcytosed into the fetal body during the last two trimesters of pregnancy. The long series of the therapeutic monoclonal antibodies and conjugates has not been tested systematically yet. The available data are summarised in this chapter.

The innate immunity plays an important role in fetal defence. The concentration of interferon is relative high in the placenta. This is probably one reason, why the therapeutic interferon treatment of the mother does not impair the fetal development.

Successful management of obstructive jaundice due to gallstones with eculizumab in a patient with paroxysmal nocturnal hemoglobinuria

Paroxysmal nocturnal hemoglobinuria (PNH) makes patients susceptible to intravascular hemolysis and thrombosis, and it can be life-threatening in stressful situations. Eculizumab, a humanized monoclonal antibody that inhibits the complement protein C5, has been evaluated as a novel therapy for PNH. We herein describe the case of a 59-year-old Japanese woman with classic PNH, who had been successfully treated with eculizumab, but who later developed acute cholecystitis/cholangitis from gallstones. Although the severe obstructive jaundice requiring endoscopic therapy following cholecystectomy was complicated, critical intravascular hemolysis and thrombosis were not observed. Therefore, utilizing eculizumab during the peri-operative management of PNH patients should be carefully taken into consideration.

Eculizumab in the treatment of atypical hemolytic uremic syndrome in infants

A 28-day-old male newborn weighing 3.6 kg was given a diagnosis of atypical hemolytic-uremic syndrome, new-onset thrombotic microangiopathy (TMA; hemoglobin, 7.7 g/dL; schistocytes, 9%), thrombocytopenia (platelets, 49 × 10(3)/μL [49 × 10(9)/L]), and acute kidney failure (serum creatinine, 1.13 mg/dL [99.8 μmol/L], corresponding to estimated glomerular filtration rate [eGFR] of 15 mL/min/1.73 m(2) [0.25 mL/s/1.73 m(2)]). Repeated high-volume plasma infusions were ineffective. Plasma exchange was attempted, but not tolerated. The patient required mechanical ventilation and continuous renal replacement therapy. He developed multiple intestinal perforations and leg skin necrosis due to systemic TMA. A low C3 level (36 mg/dL) suggested complement activation. Eculizumab, 300 mg, was administered, and within 48 hours the patient recovered from acute kidney failure, with complete hematologic remission 2 weeks later. The infant, 14 months old at the time of writing, continues to receive eculizumab, 300 mg, every 3 weeks; he is free of disease activity and has a normal creatinine level of 0.2 mg/dL (17.68 μmol/L; corresponding to eGFR of 110 mL/min/1.73 m(2) [1.83 mL/s/1.73 m(2)]), but mild proteinuria (urinary protein-creatine ratio, 1 mg/g). Results of additional studies, including probing for cobalamin anomalies and measuring levels of ADAMTS13, complement factor H (CFH), factor I (CFI), and membrane cofactor protein (MCP), were unremarkable. Antibodies to CFH were undetectable, and mutation testing of the genes for CFH, CFI, and MCP gave negative results. Treatment with eculizumab was life saving, and with continued treatment, the patient showed sustained freedom from clinical TMA complications.

Drugs that inhibit complement

The complement system is an important part of the innate immune system. Complement plays a crucial role in the pathophysiology of many disorders. Despite the pivotal role of the complement system, an approved targeted inhibitor of a complement factor became available only recently. Eculizumab is a humanized monoclonal antibody that inhibits complement factor C5. It is a targeted, disease modifying, treatment of paroxysmal nocturnal hemoglobinuria (PNH). It was approved be the US FDA and the European Commission in 2007. In this review we will update the experience with eculizumab in PNH and discuss potential use of eculizumab in other disorders (e.g. cold agglutinin disease; atypical HUS) and new approaches to complement inhibition with drugs other than eculizumab.

Terminal complement inhibition decreases antibody-mediated rejection in sensitized renal transplant recipients

Sensitized renal transplant recipients with high levels of donor-specific alloantibody (DSA) commonly develop antibody-mediated rejection (AMR), which may cause acute graft loss or shorten allograft survival. We examined the efficacy of terminal complement inhibition with the humanized anti-C5 antibody, eculizumab, in the prevention AMR in renal transplant recipients with a positive crossmatch against their living donor. The incidence of biopsy-proven AMR in the first 3 months posttransplant in 26 highly sensitized recipients of living donor renal transplants who received eculizumab posttransplant was compared to a historical control group of 51 sensitized patients treated with a similar plasma exchange (PE)-based protocol without eculizumab. The incidence of AMR was 7.7% (2/26) in the eculizumab group compared to 41.2% (21/51) in the control group (p = 0.0031). Eculizumab also decreased AMR in patients who developed high levels of DSA early after transplantation that caused proximal complement activation. With eculizumab, AMR episodes were easily treated with PE reducing the need for splenectomy. On 1-year protocol biopsy, transplant glomerulopathy was found to be present in 6.7% (1/15) eculizumab-treated recipients and in 35.7% (15/42) of control patients (p = 0.044). Inhibition of terminal complement activation with eculizumab decreases the incidence of early AMR in sensitized renal transplant recipients (ClincalTrials.gov number NCT006707).

Targeted delivery of TLR ligands to human and mouse dendritic cells strongly enhances adjuvanticity

Effective vaccines consist of 2 components: immunodominant antigens and effective adjuvants. Whereas it has been demonstrated that targeted delivery of antigens to dendritic cells (DCs) improves vaccine efficacy, we report here that co-targeting of TLR ligands (TLRLs) to DCs strongly enhances adjuvanticity and immunity. We encapsulated ligands for intracellular TLRs within biodegradable nanoparticles coated with Abs recognizing DC-specific receptors. Targeted delivery of TLRLs to human DCs enhanced the maturation and production of immune stimulatory cytokines and the Ag-specific activation of naive CD8(+) T cells. In vivo studies demonstrated that nanoparticles carrying Ag induced cytotoxic T-lymphocyte responses at 100-fold lower adjuvant dose when TLRLs were co-encapsulated instead of administered in soluble form. Moreover, the efficacy of these targeted TLRLs reduced the serum cytokine storm and related toxicity that is associated with administration of soluble TLRLs. We conclude that the targeted delivery of adjuvants may improve the efficacy and safety of DC-based vaccines.

The pathophysiology of paroxysmal nocturnal hemoglobinuria and treatment with eculizumab

Paroxysmal nocturnal hemoglobinuria is a rare disorder of hemopoietic stem cells. Affected individuals have a triad of clinical associations – intravascular hemolysis, an increased risk of thromboembolism, and bone marrow failure. Most of the symptoms experienced in this disease occur due to the absence of complement regulatory proteins on the surface of the red blood cells. Complement activation is thus not checked and causes destruction of these cells. Eculizumab is a monoclonal antibody treatment which specifically binds to the complement protein C5, preventing its cleavage, and so halts the complement cascade and prevents the formation of the terminal complement proteins. Eculizumab prevents intravascular hemolysis, stabilizes hemoglobin levels, reduces or stops the need for blood transfusions, and improves fatigue and patient quality of life as well as reducing pulmonary hypertension, decreasing the risk of thrombosis and protecting against worsening renal function. It is not a curative therapy but has a great benefit on those with this rare debilitating condition.

Anticomplement therapy

The complement system is an important part of innate immunity; however, as with other parts of the immune system, the complement system can become pathologically activated and create or worsen disease. Anticomplement reagents have been studied for several years, but only recently have they emerged as a viable therapeutic tool. Here, we describe the role of the complement system in a wide array of diseases, as well as the use of anticomplement therapy as treatment for these diseases in animal models and in human clinical trials. Specifically, we will discuss the role of anticomplement therapy in paroxysmal nocturnal hemoglobinuria, glomerulonephritis, and heart disease, including coronary artery disease, myocardial infarction, and coronary revascularization procedures such as percutaneous coronary angioplasty and coronary artery bypass graft surgery.

The influence of PEG chain length and targeting moiety on antibody-mediated delivery of nanoparticle vaccines to human dendritic cells

Targeted delivery of nanoparticles (NPs) carrying vaccine components to dendritic cells (DCs) is a promising strategy to initiate antigen-specific immune responses. Improving the interactions between nanoparticle-carried ligands and receptors on DCs is a major challenge. These NPs are generally coated with poly(ethylene glycol) (PEG), to shield non-specific interactions, and antibodies, to facilitate specific delivery to DC surface receptors. We have devised a strategy to covalently link PEG molecules of various chain length (Mw 2000-20000 g/moL) to poly(lactic-co-)glycolic acid (PLGA) NP vaccines. We coated these NPs with various antibodies recognizing the DC-specific receptor DC-SIGN to study the effects of shielding and antibody type on antibody--receptor interactions. Chemical attachment of PEG to the particle surface was followed by detailed zeta potential, DLS and NMR studies, and analyzed by analytical chemistry. Increasing the PEG chain length increased particle size and polydispersity index and reduced the intracellular degradation rate of encapsulated antigens. Binding and uptake of NPs by human DCs was affected by both PEG chain length and antibody type. NPs coated with PEG-3000 had the optimal chain length for antibody--receptor interactions and induction of antigen-specific T-cell responses. Interestingly, clear differences were observed upon targeting distinct epitopes of the same receptor. Binding and uptake of NPs carrying antibodies recognizing the carbohydrate recognition domain of DC-SIGN was enhanced when compared to those carrying antibodies recognizing the receptor's neck region. In conclusion, our data show that PEG chains cannot be extended beyond a certain length for shielding purposes without compromising the efficacy of targeted delivery. Thereby, the implications of our findings are not limited to the future design of nanovaccines specifically targeted to DC-SIGN, but apply to the general design of targeted nanocarriers.

Prompt reversal of a severe complement activation by eculizumab in a patient undergoing intentional ABO-incompatible pancreas and kidney transplantation

We describe the presumably first intentional ABO-incompatible deceased-donor kidney and pancreas transplantation with a severe antibody-mediated rejection during a rebound of isoagglutinins. Rejection was successfully treated with eculizumab, which inhibits the terminal pathway of complement. Complement analysis (C3, C3d,g, and a modified assay of classical complement-related hemolytic function) documented complement activation and confirmed that eculizumab completely blocked complement function. At 6 months, the patient had normal kidney and pancreas function, and histological evaluations revealed no evidence of sustained graft damage. This successful transplantation suggests that ABO barriers can safely be overcome without extensive preconditioning, when the complement inhibitor eculizumab is included.

Chronic treatment of paroxysmal nocturnal hemoglobinuria patients with eculizumab: safety, efficacy, and unexpected laboratory phenomena

The terminal complement inhibitor eculizumab has become the standard of treatment in patients with symptomatic paroxysmal nocturnal hemoglobinuria (PNH). In this retrospective study, 19 PNH patients received chronic therapy with eculizumab with a median duration of 16 months (range 6-46 months). Parameters of hemolysis, transfusion requirements, and serum iron parameters were analyzed. Lactate dehydrogenase levels were significantly decreased by 85% from a median of 1897 U/l (range 293-3360) to 283 U/l (range 143-667), with an 86% reduction of transfusion requirements, whereas other parameters of hemolysis remained abnormal. Six patients (31.6%) became completely transfusion independent. A significant increase in ferritin levels from a median of 104 μg/l before to a median of 528 μg/l (p = 0.011) during treatment with eculizumab was observed. This was more pronounced in patients with low reticulocyte production index and/or requiring blood transfusions. Monospecific direct Coombs test was positive in most PNH patients, indicating a shift to extravascular hemolysis. Positive immunofixation for IgG kappa was observed, due to the presence of eculizumab in the serum. Eculizumab was safe and well tolerated long term in our study population. Iron should not be routinely supplemented in PNH patients treated with eculizumab without close monitoring of iron parameters, and iron depletion therapy should be considered in the case of overload.

Inhibiting the C5-C5a receptor axis

Activation of the complement system is a major pathogenic event that drives various inflammatory responses in numerous diseases. All pathways of complement activation lead to cleavage of the C5 molecule generating the anaphylatoxin C5a and, C5b that subsequently forms the terminal complement complex (C5b-9). C5a exerts a predominant pro-inflammatory activity through interactions with the classical G-protein coupled receptor C5aR (CD88) as well as with the non-G protein coupled receptor C5L2 (GPR77), expressed on various immune and non-immune cells. C5b-9 causes cytolysis through the formation of the membrane attack complex (MAC), and sub-lytic MAC and soluble C5b-9 also possess a multitude of non-cytolytic immune functions. These two complement effectors, C5a and C5b-9, generated from C5 cleavage, are key components of the complement system responsible for propagating and/or initiating pathology in different diseases, including paroxysmal nocturnal hemoglobinuria, rheumatoid arthritis, ischemia-reperfusion injuries and neurodegenerative diseases. Thus, the C5-C5a receptor axis represents an attractive target for drug development. This review provides a comprehensive analysis of different methods of inhibiting the generation of C5a and C5b-9 as well as the signalling cascade of C5a via its receptors. These include the inhibition of C5 cleavage through targeting of C5 convertases or via the C5 molecule itself, as well as blocking the activity of C5a by neutralizing antibodies and pharmacological inhibitors, or by targeting C5a receptors per se. Examples of drugs and naturally occurring compounds used are discussed in relation to disease models and clinical trials. To date, only one such compound has thus far made it to clinical medicine: the anti-C5 antibody eculizumab, for treating paroxysmal nocturnal hemoglobinuria. However, a number of drug candidates are rapidly emerging that are currently in early-phase clinical trials. The C5-C5a axis as a target for drug development is highly promising for the treatment of currently intractable major human diseases.

Long-term treatment with eculizumab in paroxysmal nocturnal hemoglobinuria: sustained efficacy and improved survival

Paroxysmal nocturnal hemoglobinuria (PNH) is an acquired clonal hematopoietic disorder with increased mortality and morbidity resulting from intravascular hemolysis. Eculizumab, a monoclonal antibody against the complement protein 5, stops the intravascular hemolysis in PNH. We evaluated 79 consecutive patients treated with eculizumab in Leeds between May 2002 and July 2010. The survival of patients treated with eculizumab was not different from age- and sex-matched normal controls (P = .46) but was significantly better than 30 similar patients managed before eculizumab (P = .030). Three patients on eculizumab, all over 50 years old, died of causes unrelated to PNH. Twenty-one patients (27%) had a thrombosis before starting eculizumab (5.6 events per 100 patient-years) compared with 2 thromboses on eculizumab (0.8 events per 100 patient-years; P < .001). Twenty-one patients with no previous thrombosis discontinued warfarin on eculizumab with no thrombotic sequelae. Forty of 61 (66%) patients on eculizumab for more than 12 months achieved transfusion independence. The 12-month mean transfusion requirement reduced from 19.3 units before eculizumab to 5.0 units in the most recent 12 months on eculizumab (P < .001). Eculizumab dramatically alters the natural course of PNH, reducing symptoms and disease complications as well as improving survival to a similar level to that of the general population.

Multimodal imaging of nanovaccine carriers targeted to human dendritic cells

Dendritic cells (DCs) are key players in the initiation of adaptive immune responses and are currently exploited in immunotherapy against cancer and infectious diseases. The targeted delivery of nanovaccine particles (NPs) to DCs in vivo is a promising strategy to enhance immune responses. Here, targeted nanovaccine carriers were generated that allow multimodal imaging of nanocarrier-DC interactions from the subcellular to the organism level. These carriers were made of biodegradable poly(D,L-lactide-co-glycolide) harboring superparamagnetic iron oxide particles (SPIO) and fluorescently labeled antigen in a single particle. Targeted delivery was facilitated by coating the NPs with antibodies recognizing the DC-specific receptor DC-SIGN. The fluorescent label allowed for rapid analysis and quantification of specific versus nonspecific uptake of targeted NPs by DCs compared to other blood cells. In addition, it showed that part of the encapsulated antigen reached the lysosomal compartment of DCs within 24 h. Moreover, the presence of fluorescent label did not prevent the antigen from being presented to antigen-specific T cells. The incorporated SPIO was applied to track the NPs at subcellular cell organel level using transmission electron microscopy (TEM). NPs were found within endolysosomal compartments, where part of the SPIO was already released within 24 h. Furthermore, part of the NPs seemed to localize within the cytoplasm. Ex vivo loading of DCs with NPs resulted in efficient labeling and detection by MRI and did not abolish cell migration within collagen scaffolds. In conclusion, incorporation of two imaging agents within a single carrier allows tracking of targeted nanovaccines on a subcellular, cellular and possibly organism level, thereby facilitating rational design of in vivo targeted vaccination strategies.

Safety and efficacy of the terminal complement inhibitor eculizumab in Japanese patients with paroxysmal nocturnal hemoglobinuria: the AEGIS clinical trial

Paroxysmal nocturnal hemoglobinuria (PNH) is a progressive and life-threatening disease characterized by complement-mediated chronic hemolysis, resulting in serious life-threatening complications and early mortality. Eculizumab, a humanized anti-C5 monoclonal antibody that inhibits terminal complement activation, has been shown to reduce hemolysis in PNH patients. The pivotal open-label, 12-week phase II registration study (AEGIS) was designed to evaluate the efficacy and safety of eculizumab in Japanese patients with PNH. This trial achieved its primary endpoint of reducing intravascular hemolysis with high statistical significance. Twenty-seven of the 29 patients responded to eculizumab treatment, resulting in an 87% reduction in hemolysis (P < 0.0001) and subsequent improvement in anemia (P = 0.0003) despite reduction in transfusion requirements (P = 0.006). Fatigue and dyspnea significantly improved within 1-2 weeks of eculizumab treatment and the improvement was independent of changes in hemoglobin. Chronic kidney disease (CKD) was common (66%) and eculizumab treatment improved CKD in 41% of patients at 12 weeks (P < 0.001). Elevated thrombotic risk was evident in Japanese PNH patients and eculizumab treatment normalized D: -dimer levels in 45% of patients with elevated D: -dimers at baseline (P < 0.001). The AEGIS results demonstrate that eculizumab is effective, safe and well tolerated in Japanese patients with PNH.

A recombinant vaccine effectively induces c5a-specific neutralizing antibodies and prevents arthritis

Objectives

To develop and validate a recombinant vaccine to attenuate inflammation in arthritis by sustained neutralization of the anaphylatoxin C5a.

Methods

We constructed and expressed fusion protein of C5a and maltose binding protein. Efficacy of specific C5a neutralization was tested using the fusion protein as vaccine in three different arthritis mouse models: collagen induced arthritis (CIA), chronic relapsing CIA and collagen antibody induced arthritis (CAIA). Levels of anti-C5a antibodies and anti-collagen type II were measured by ELISA. C5a neutralization assay was done using a rat basophilic leukemia cell-line transfected with the human C5aR. Complement activity was determined using a hemolytic assay and joint morphology was assessed by histology.

Results

Vaccination of mice with MBP-C5a led to significant reduction of arthritis incidence and severity but not anti-collagen antibody synthesis. Histology of the MBP-C5a and control (MBP or PBS) vaccinated mice paws confirmed the vaccination effect. Sera from the vaccinated mice developed C5a-specific neutralizing antibodies, however C5 activation and formation of the membrane attack complex by C5b were not significantly altered.

Conclusions

Exploitation of host immune response to generate sustained C5a neutralizing antibodies without significantly compromising C5/C5b activity is a useful strategy for developing an effective vaccine for antibody mediated and C5a dependent inflammatory diseases. Further developing of such a therapeutic vaccine would be more optimal and cost effective to attenuate inflammation without affecting host immunity.

Treatment with the C5a receptor antagonist ADC-1004 reduces myocardial infarction in a porcine ischemia-reperfusion model

BACKGROUND

Polymorphonuclear neutrophils, stimulated by the activated complement factor C5a, have been implicated in cardiac ischemia/reperfusion injury. ADC-1004 is a competitive C5a receptor antagonist that has been shown to inhibit complement related neutrophil activation. ADC-1004 shields the neutrophils from C5a activation before they enter the reperfused area, which could be a mechanistic advantage compared to previous C5a directed reperfusion therapies. We investigated if treatment with ADC-1004, according to a clinically applicable protocol, would reduce infarct size and microvascular obstruction in a large animal myocardial infarct model.

METHODS

In anesthetized pigs (42-53 kg), a percutaneous coronary intervention balloon was inflated in the left anterior descending artery for 40 minutes, followed by 4 hours of reperfusion. Twenty minutes after balloon inflation the pigs were randomized to an intravenous bolus administration of ADC-1004 (175 mg, n = 8) or saline (9 mg/ml, n = 8). Area at risk (AAR) was evaluated by ex vivo SPECT. Infarct size and microvascular obstruction were evaluated by ex vivo MRI. The observers were blinded to the treatment at randomization and analysis.

RESULTS

ADC-1004 treatment reduced infarct size by 21% (ADC-1004: 58.3 ± 3.4 vs control: 74.1 ± 2.9%AAR, p = 0.007). Microvascular obstruction was similar between the groups (ADC-1004: 2.2 ± 1.2 vs control: 5.3 ± 2.5%AAR, p = 0.23). The mean plasma concentration of ADC-1004 was 83 ± 8 nM at sacrifice. There were no significant differences between the groups with respect to heart rate, mean arterial pressure, cardiac output and blood-gas data.

CONCLUSIONS

ADC-1004 treatment reduces myocardial ischemia-reperfusion injury and represents a novel treatment strategy of myocardial infarct with potential clinical applicability.

Therapeutic monoclonal antibody concentration monitoring: free or total?

Most therapeutic monoclonal antibodies are designed to bind a specific antigen to elicit pharmacological effects. Accurate quantification of a therapeutic monoclonal antibody in biological matrices is essential for assessing its pharmacokinetics and selecting an effective dosing regimen. Therapeutic antibodies may exist in free, partially bound and fully bound forms in the bloodstream. The choice of which form(s) to measure and how to measure them is gaining much attention with the increase in the number of soluble therapeutic targets. This article will review the bioanalytical methods used in supporting the clinical development of the US FDA-approved therapeutic monoclonal antibodies and also discuss how different factors, such as assay format, target and antibody concentrations, and sample dilutions, can have an impact on the measurement of each form of antibody. Appreciation of which form of drug is being measured and what factors may impact measurement under different conditions are important for interpretation of the pharmacokinetics of therapeutic antibodies.

Managing a pregnant patient with paroxysmal nocturnal hemoglobinuria in the era of eculizumab

Paroxysmal nocturnal hemoglobinuria (PNH) is a rare clonal stem cell disorder, which affects women of child-bearing age. PNH is associated with thrombotic complications, which are the main causes of morbidity and mortality. Management of a pregnant woman with PNH remains a challenge due to high incidence of thrombotic complications and the difficulty of differentiating a PNH crisis from the complications of pregnancy. PNH is associated with an increased rate of premature labor and fetal loss. Eculizumab, a humanized monoclonal antibody directed against the terminal complement protein C5, has revolutionized treatment of PNH. However, the role of eculizumab in pregnancy is unclear. We review the current strategies for the management of pregnant women with PNH, underline the controversies and present our recommendations.

Innate immunity and rheumatoid arthritis

Innate immunity, with macrophages playing a central role, is critically important in the pathogenesis of RA. Although environmental insults such as smoking have been implicated in the initiation of rheumatoid arthritis (RA) in patients who express the shared epitope, the understanding of the role of innate immunity in the pathogenesis of this disease is also expanding. As the understanding continues to expand, enticing targets for new therapeutic interventions continue to be identified. This article focuses on cells of myelomonocytic origin, their receptors, and factors that interact with them.

Targeted PLGA nano- but not microparticles specifically deliver antigen to human dendritic cells via DC-SIGN in vitro

Vaccine efficacy is strongly enhanced by antibody-mediated targeting of vaccine components to dendritic cells (DCs), which are professional antigen presenting cells. However, the options to link antigens or immune modulators to a single antibody are limited. Here, we engineered versatile nano- and micrometer-sized slow-release vaccine delivery vehicles that specifically target human DCs to overcome this limitation. The nano- (NPs) and microparticles (MPs), with diameters of approximately 200nm and 2microm, consist of a PLGA core coated with a polyethylene glycol-lipid layer carrying the humanized targeting antibody hD1, which does not interact with complement or Fc receptors and recognizes the human C-type lectin receptor DC-SIGN on DCs. We studied how these particles interact with human DCs and blood cells, as well as the kinetics of PLGA-encapsulated antigen degradation within DCs. Encapsulation of antigen resulted in almost 38% degradation for both NPs and MPs 6days after particle ingestion by DCs, compared to 94% when nonencapsulated, soluble antigen was used. In contrast to the MPs, which were taken up rather nonspecifically, the NPs effectively targeted human DCs. Consequently, targeted delivery only improved antigen presentation of NPs and induced antigen-dependent T cell responses at 10-100 fold lower concentrations than nontargeted NPs.

Eculizumab prevents intravascular hemolysis in patients with paroxysmal nocturnal hemoglobinuria and unmasks low-level extravascular hemolysis occurring through C3 opsonization

BACKGROUND

Paroxysmal nocturnal hemoglobinuria is an acquired hemolytic anemia characterized by intravascular hemolysis which has been demonstrated to be effectively controlled with eculizumab. However, lactate dehydrogenase levels remain slightly elevated and haptoglobin levels remain low in some patients suggesting residual low-level hemolysis. This may be due to C3-mediated clearance of paroxysmal nocturnal hemoglobinuria red blood cells through the reticuloendothelial system.

DESIGN AND METHODS

Thirty-nine samples from patients not treated with eculizumab and 31 samples from patients treated with eculizumab were obtained (for 17 of these 31 samples there were also samples taken prior to eculizumab treatment). Membrane bound complement was assessed by flow cytometry. Direct antiglobulin testing was carried out using two methods. Lactate dehydrogenase was assayed to assess the degree of hemolysis.

RESULTS

Three of 39 patients (8%) with paroxysmal nocturnal hemoglobinuria not on eculizumab had a positive direct antiglobulin test, while the test was positive in 21 of 31 (68%) during eculizumab treatment. Of these 21 patients who had a positive direct antiglobulin test during eculizumab treatment, 17 had been tested prior to treatment; only one was positive. Flow cytometry using anti-C3 monoclonal antibodies was performed on the 21 direct antiglobulin test-positive, eculizumab-treated patients; the median proportion of C3-positive total red blood cells was 26%. Among the eculizumab-treated patients, 16 of the 21 (76.2%) with a positive direct antiglobulin test received at least one transfusion compared with one of ten (10.0%) of those with a negative test (P<0.01). Among the eculizumab-treated patients, the mean hemoglobin value for the 21 with a positive direct antiglobulin test was 9.6+/-0.3 g/dL, whereas that in the ten patients with a negative test was 11.0+/-0.4 g/dL (P=0.02).

CONCLUSIONS

These data demonstrate a previously masked mechanism of red cell clearance in paroxysmal nocturnal hemoglobinuria and suggests that blockade of complement at C5 allows C3 fragment accumulation on some paroxysmal nocturnal hemoglobinuria red cells, explaining the residual low-level hemolysis occurring in some eculizumab-treated patients.

Complement inhibitor eculizumab in atypical hemolytic uremic syndrome

BACKGROUND AND OBJECTIVES

Atypical hemolytic uremic syndrome (aHUS) is associated with a congenital or acquired dysregulation of the complement alternative pathway that leads to continuous complement activation on host cells causing inflammation and damage. Eculizumab, a humanized mAb against complement protein C5, inhibits activation of the terminal complement pathway.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

We report an adolescent with relapsing unclassified aHUS. On admission, a high plasma creatinine level indicated a poor prognosis, and hemodialysis had to be started. Plasma exchanges were initially effective against the microangiopathic hemolytic activity and allowed a temporary improvement of renal function with termination of hemodialysis after 7 wk. Subsequently, plasma exchanges (three times per week) failed to prevent ongoing aHUS activity and progressive renal failure. After 12 wk, aHUS treatment was switched to eculizumab.

RESULTS

Eculizumab was effective in terminating the microangiopathic hemolytic process in two aHUS relapses; however, after normalization of complement activity, aHUS recurred and ultimately led to anuric end-stage renal failure.

CONCLUSIONS

In this patient, complement inhibition by eculizumab temporarily terminated the microangiopathic hemolytic activity. Nevertheless, renal damage as a result of preceding and subsequent aHUS activity resulted in end-stage renal failure; therefore, therapeutic success may depend on early administration of eculizumab. The optimal duration of treatment may be variable and remains to be determined.

Potential aggregation prone regions in biotherapeutics: A survey of commercial monoclonal antibodies

Aggregation of a biotherapeutic is of significant concern and judicious process and formulation development is required to minimize aggregate levels in the final product. Aggregation of a protein in solution is driven by intrinsic and extrinsic factors. In this work we have focused on aggregation as an intrinsic property of the molecule. We have studied the sequences and Fab structures of commercial and non-commercial antibody sequences for their vulnerability towards aggregation by using sequence based computational tools to identify potential aggregation-prone motifs or regions. The mAbs in our dataset contain 2 to 8 aggregation-prone motifs per heavy and light chain pair. Some of these motifs are located in variable domains, primarily in CDRs. Most aggregation-prone motifs are rich in beta branched aliphatic and aromatic residues. Hydroxyl-containing Ser/Thr residues are also found in several aggregation-prone motifs while charged residues are rare. The motifs found in light chain CDR3 are glutamine (Q)/asparagine (N) rich. These motifs are similar to the reported aggregation promoting regions found in prion and amyloidogenic proteins that are also rich in Q/N, aliphatic and aromatic residues. The implication is that one possible mechanism for aggregation of mAbs may be through formation of cross-beta structures and fibrils. Mapping on the available Fab-receptor/antigen complex structures reveals that these motifs in CDRs might also contribute significantly towards receptor/antigen binding. Our analysis identifies the opportunity and tools for simultaneous optimization of the therapeutic protein sequence for potency and specificity while reducing vulnerability towards aggregation.

Homology modelling and bivalent single-chain Fv construction of anti-HepG2 single-chain immunoglobulin Fv fragments from a phage display library

We prepared single-chain immunoglobulin Fv fragments (scFv) SLH10 specific for the HepG2 cell line after biopanning from a large human-naive phage display library (Griffin. 1 Library). The three-dimensional (3D) structure of SLH10 was modelled by the Insight II molecule simulation software.The structure was refined using the molecular dynamics method.The structures with the least steric clashes and lowest energy were determined finally. The optimized structures of heavy (VH) and light (VL) variable chains of SLH10 scFv were obtained.Then SLH10 bivalent single-chain Fv (BsFv) was constructed that would be suitable for high-affinity targeting.SLH10 BsFv was generated by linking scFvs together and identified by sequencing. Its expression products were confirmed by western blot analysis.The relative molecular masses of scFv and BsFv were approximately 30 kDa and 60 kDa,respectively. Flow cytometry revealed that SLH10 BsFv bound the selected cell lines with greater signal intensity than the parental scFv. The improved antigen binding of SLH10 BsFv may be useful for immunodiagnostics or targeted gene therapy for liver cancer.

Eculizumab for paroxysmal nocturnal haemoglobinuria

The complement system plays a central part in both innate and acquired immunity, but the contribution of complement activation to pathobiology is largely ancillary. An exception to the non-dominant role of complement in disease is the haemolytic anaemia of paroxysmal nocturnal haemoglobinuria (PNH). The intravascular haemolysis that is the clinical hallmark of PNH is a consequence of deficiency of the complement inhibitory proteins decay accelerating factor (DAF, CD55) and membrane inhibitor of reactive lysis (MIRL, CD59). Eculizumab is a humanised monoclonal antibody that binds and prevents activation of complement C5 and the subsequent formation of the cytolytic membrane attack complex of complement. Eculizumab inhibits the intravascular haemolysis of PNH, reduces transfusion requirements, stabilises haemoglobin concentration, and improves quality of life. Although chronic treatment with eculizumab increases the risk of infections with Neisseria meningitides, the drug is generally safe and well tolerated. But as is the case with other drugs developed for treatment of ultra-orphan diseases, eculizumab is expensive, and treatment must continue indefinitely because C5 inhibition does not affect the process (ie, clonal proliferation of haemopoietic stem cells with a mutant phosphatidylinositol glycan complementation class A [PIGA] gene) that underlies PNH. Moreover, due to the heterogeneous nature of the disease, treatment with eculizumab is not appropriate for all patients with PNH.

The management of paroxysmal nocturnal hemoglobinuria: recent advances in diagnosis and treatment and new hope for patients

PNH is a rare clonal hematopoietic stem disorder clinically characterized by the triad of chronic complement-mediated hemolysis, thrombosis, and bone marrow failure. While median survival has improved when historical data are compared to more recent data, thrombosis, the major cause of death in PNH, is still observed in approximately 40% of patients. The symptoms associated with this disorder–including fatigue, pain, esophageal spasm, and erectile dysfunction–are often severe and disabling. While PNH may be a curiosity to the physician, it forces the majority of patients to significantly modify their lives. Transplantation represents a curative option; however, the risks associated with this option are not insignificant. Eculizumab has been shown to significantly reduce hemolysis, improve anemia, reduce transfusion requirements, and significantly improve fatigue and other QoL scores. Clearly, targeted complement inhibition by eculizumab has the promise to significantly improve the lives of patients with PNH.

Eculizumab, a terminal complement inhibitor, improves anaemia in patients with paroxysmal nocturnal haemoglobinuria

In paroxysmal nocturnal haemoglobinuria (PNH), chronic destruction of PNH red blood cells (RBCs) by complement leads to anaemia and other serious morbidities. Eculizumab inhibits terminal complement-mediated PNH RBC destruction by targeting C5. In the phase III, double-blind, placebo-controlled, TRIUMPH study, eculizumab reduced haemolysis, stabilized haemoglobin levels, reduced transfusion requirements and improved fatigue in patients with PNH. Herein, we explored the effects of eculizumab on measures of anaemia in patients from the TRIUMPH study and the open-label SHEPHERD study, a more heterogeneous population. Eculizumab reduced haemolysis regardless of pretreatment transfusion requirements and regardless of whether or not patients became transfusion-dependent during treatment (P < 0.001). Reduction in haemolysis was associated with increased PNH RBC counts (P < 0.001) while reticulocyte counts remained elevated. Eculizumab-treated patients demonstrated significantly higher levels of haemoglobin as compared with placebo in TRIUMPH and relative to baseline levels in SHEPHERD (P < 0.001 for each study). Eculizumab lowered transfusion requirement across multiple pretreatment transfusion strata and eliminated transfusion support in a majority of both TRIUMPH and SHEPHERD patients (P < 0.001). Patients who required some transfusion support during treatment with eculizumab showed a reduction in haemolysis and transfusion requirements and an improvement in fatigue. Eculizumab reduces haemolysis and improves anaemia and fatigue, regardless of transfusion requirements.