Anticomplement Therapeutics Research Articles

Novel anti-complement therapeutics for hemolytic anemia

The anti-C5 antibody eculizumab was approved in 2007 as the first anti-complement agent for the treatment of paroxysmal nocturnal hemoglobinuria (PNH). While eculizumab's indication has been expanded to include other diseases, the development of new anti-complement agents has been aggressively pursued for various diseases. In PNH, the anti-C5 recycling antibody ravulizumab, which is an improved version of eculizumab, has been developed, with an extended dosing interval of 2 to 8 weeks, vastly improving convenience. The treatment of PNH with terminal complement inhibitors such as eculizumab and ravulizumab presents a new challenge-extravascular hemolysis. To address this issue, the proximal complement inhibitor, a C3 inhibitor called pegcetacoplan, was approved in the United States of America. Furthermore, the amplification loop inhibitors-a factor B inhibitor iptacopan, and a factor D inhibitor danicopan-are being developed. Recently, the anti-C1s antibody sutimlimab was approved for the treatment of cold agglutinin disease, a type of autoimmune hemolytic anemia. This article discusses novel anti-complement therapies for hemolytic anemia.

Complement in autoimmune inflammatory myopathies, the role of myositis-associated antibodies, COVID-19 associations and muscle amyloid deposits

Introduction The inflammatory myopathies (IM) have now evolved into distinct subsets requiring clarification about their immunopathogenesis to guide applications of targeted therapies Areas covered Immunohistopathologic criteria of IM with focus on complement, anti-complement therapeutics and other biologic immunotherapies. The COVID19-triggered muscle autoimmunity along with the correct interpretation of muscle amyloid deposits are discussed. Expert opinion The IM, unjustifiably referred as idiopathic, comprise Dermatomyositis (DM), Necrotizing Autoimmune Myositis (NAM), Anti-synthetase syndrome-overlap myositis (Anti-SS-OM), and Inclusion-Body-Myositis (IBM). In DM, complement activation with MAC-mediated endomysial microvascular destruction and perifascicular atrophy is the fundamental process, while innate immunity activation factors, INF1 and MxA, sense and secondarily enhance inflammation. Complement participates in muscle fiber necrosis from any cause and may facilitate muscle-fiber necrosis in NAM but seems unlikely that myositis-associated antibodies participate in complement-fixing. Accordingly, anti-complement therapeutics should be prioritized for DM. SARS-CoV-2 can potentially trigger muscle autoimmunity but systematic studies are needed as the reported autopsy findings are not clinically relevant. In IBM, tiny amyloid deposits within muscle fibers are enhanced by inflammatory mediators contributing to myodegeneration; in contrast, spotty amyloid deposits in the endomysial connective tissue do not represent “amyloid myopathy” but only have diagnostic value for amyloidosis due to any cause.

Immune-mediated necrotizing myopathy: clinical features and pathogenesis.

Immune-mediated necrotizing myopathy (IMNM) is a group of inflammatory myopathies that was distinguished from polymyositis in 2004. Most IMNMs are associated with anti-signal recognition particle (anti-SRP) or anti-3-hydroxy-3-methylglutaryl-coA reductase (anti-HMGCR) myositis-specific autoantibodies, although ~20% of patients with IMNM remain seronegative. These associations have led to three subclasses of IMNM: anti-SRP-positive IMNM, anti-HMGCR-positive IMNM and seronegative IMNM. IMNMs are frequently rapidly progressive and severe, displaying high serum creatine kinase levels, and failure to treat IMNMs effectively may lead to severe muscle impairment. In patients with seronegative IMNM, disease can be concomitant with cancer. Research into IMNM pathogenesis has shown that anti-SRP and anti-HMGCR autoantibodies cause weakness and myofibre necrosis in mice, suggesting that, as well as being diagnostic biomarkers of IMNM, they may play a key role in disease pathogenesis. Therapeutically, treatments such as rituximab or intravenous immunoglobulins can now be discussed for IMNM, and targeted therapies, such as anticomplement therapeutics, may be a future option for patients with refractory disease.

Complement system activation and peritoneal membrane alterations: Culprit or innocent bystander?

Peritoneal dialysis (PD) accounts for approximately 10% of the dialysis population worldwide. Major concern limiting long-term PD success is the loss of the peritoneal membrane function after prolonged exposure to dialysis solutions. The complement system is a major component of the innate immune system, which provides a first-line defense against pathogens. Uncontrolled activation of the complement system directly contributes to the pathophysiology of rare and common kidney diseases and to a growing number of nonrenal diseases. Here, we review currently available evidence of complement activation in patients treated with PD and its association with structural and functional alterations of the peritoneal membrane. Mainly, evidence point toward a local, intraperitoneal, production of complement molecules in response to PD exposure. Dialysis fluids, particularly glucose, play a role in complement activation and dysregulation leading to untoward PD-related pathophysiological processes such as peritoneal fibrosis, angiogenesis, and vasculopathy and, perhaps, encapsulating peritoneal fibrosis development. These findings could lead to further development and use of anticomplement therapeutics in PD patients to prevent membrane damage.

Current and Future Approaches for Monitoring Responses to Anti-complement Therapeutics.

Aberrations in complement system functions have been identified as either direct or indirect pathophysiological mechanisms in many diseases and pathological conditions, such as infections, autoimmune diseases, inflammation, malignancies, and allogeneic transplantation. Currently available techniques to study complement include quantification of (a) individual complement components, (b) complement activation products, and (c) molecular mechanisms/function. An emerging area of major interest in translational studies aims to study and monitor patients on complement regulatory drugs for efficacy as well as adverse events. This area is progressing rapidly with several anti-complement therapeutics under development, in clinical trials, or already in clinical use. In this review, we summarized the appropriate indications, techniques, and interpretations of basic complement analyses, exemplified by a number of clinical disorders.

Anaphylatoxin Signaling in Retinal Pigment and Choroidal Endothelial Cells: Characteristics and Relevance to Age-Related Macular Degeneration.

Age-related macular degeneration (AMD) is the leading cause of blindness in the USA. Polymorphisms in various complement components are associated with an increased risk for AMD, and it has been hypothesized that an overactive complement system is partially responsible for the pathology of AMD. AMD is classified as early, intermediate, or late AMD, depending on the degree of the associated pathologies. Late AMD can be characterized as either lesions associated with neovascular AMD or geographic atrophy. Both sets of lesions are associated with pathology at the RPE/choroid interface, which include a thickening of Bruch's membrane, presence of drusen, and pigmentary alterations, and deterioration of the blood-retina barrier has been reported. These changes can lead to the slow degeneration and atrophy of the photoreceptors in the macula in dry AMD, or progress to choroidal neovascularization (CNV) and leakage of these new vessels in wet AMD. It has been shown previously that complement anaphylatoxins C3a and C5a, signaling via their respective G-protein-coupled receptors, can alter RPE cell function and promote choroidal neovascularization. However, it is important to note these components also play a role in tissue repair. Here we discuss anaphylatoxin signaling in AMD-related target cells and the potential implications for the design of anti-complement therapeutics.

Abstract 673: Use of membrane-tethered anti-thrombin compounds in prostate cancer therapy

Abstract The tissue factor-thrombin pathway is known to mediate proliferation, adhesion, invasion and metastasis of many types of cancer cells. These effects are additional to the thromboembolic processes commonly occurring in cancer, particularly in patients on hormonal therapies. In prostate cancer, there is an overexpression of the thrombin receptor PAR1 correlating with tumor progression. Anticoagulants such as heparin and hirudin are known to inhibit metastasis of tumors and improve survival rates in prostate cancer patients with localized disease. However, anticoagulants given systemically have an associated risk of bleeding which is higher in cancer patients and can be compounded by an increased risk of thrombocytopenia. Anticoagulants which can be localized to a tumor lesion are therefore highly favorable. The aim of the following study was to determine the efficacy of membrane-tethered anticoagulants on thrombin mediated migration and proliferation of prostate cancer cells in vitro. The hirudin cytotopic analogs PTL004 and PTL006, previously designed for use with anti-complement therapeutics in transplantation, were assessed as inhibitors of proliferation and migration of prostate cancer cells, in comparison to non-tailed hirudin-derived peptide, a PAR-1 antagonist and hirudin itself. Methods: For proliferation assays, 2000 PC3 prostate cancer cells were seeded in 96 well plates in serum free culture medium. Cells were preincubated for 30 mins with anticoagulant inhibitors at concentrations from 1 µM to 0.001 µM, and then 0.5 nM thrombin was added. Proliferation was measured after 48 hrs using MTT. To measure effects on cell migration, 10,000 PC3 cells were seeded onto porous membrane inserts in 24 well plates in serum free medium and then incubated with the inhibitors at 1 µM for 30 mins followed by 0.5 nM thrombin. Migration of cells through the membrane was measured after a 24 hr period. Results: Thrombin increased proliferation of PC3 cells in serum-free medium with a 1.5 fold increase in cell number after 48h. The tailed derivative PTL004 inhibited proliferation with an IC50 of 1 µM, equivalent to hirudin and the PAR1 antagonist. Liposomes prepared with PTL004 on the surface were more active than the tailed preparation in free solution with an IC50 10-50 fold lower. However, the non-tailed hirudin-derived peptide, and the derivative PTL006, which is known to have a more rapid dissociation rate when used with other cell types, were not active under these assay conditions. In the migration assays, PTL004 was also most active among the derivatives we tested. Conclusions: The membrane localizing anti-coagulant PTL004 has comparable anti-migratory and anti-proliferative properties to hirudin, and liposomes bearing this compound are even more effective at inhibition of proliferation of PC3 cells. The results demonstrate the potential of a cytotopic approach using tailed anticoagulants in localized prostate cancer therapy. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 673. doi:10.1158/1538-7445.AM2011-673

Integrating cytotopic strategy in transplantation: (1) Design of locally-acting coagulation inhibitors for use with anti-complement therapeutics

Integrating cytotopic strategy in transplantation: (1) Design of locally-acting coagulation inhibitors for use with anti-complement therapeutics

Tailoring anti-complement therapeutics.

Complement is a core component of the immune system, which performs vital roles in immune surveillance. However, the active products that enable complement to perform its physiological roles can inappropriately target self tissues and cause pathology. Complement-mediated inflammation and tissue destruction is an important drive to pathology in diseases as diverse as rheumatoid arthritis and dementia. Two decades ago there were no agents that could be used therapeutically to inhibit the activation of complement, but increased understanding of the natural control of complement in vivo has markedly changed this situation. The realization that drugs mimicking the action of the complement regulatory proteins present on self cells, and in plasma, could effectively control pathological activation of complement has opened the door to the use of anticomplement therapy in disease. Here we will review the development of anticomplement therapeutics from the first generation agents, which are unmodified recombinant forms of natural regulators, to recent strategies for making better drugs. We will describe strategies for targeting the anticomplement activity to the site of disease, and for extending the plasma half-life of the agent. Finally, we will illustrate a novel approach to the delivery of anticomplement agents, making prodrugs that are activated only at disease sites thus minimizing the deleterious effects of systemic complement inhibition.