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CD55 deficiency with hyperactivation of complement, angiopathic thrombosis, and protein-losing enteropathy (CHAPLE) is an ultra-rare genetic disorder characterised by intestinal lymphatic damage, lymphangiectasia, and protein-losing enteropathy caused by overactivation of the complement system. We assessed the efficacy and safety of pozelimab, an antibody blocking complement component 5.

Complement hyperactivation, angiopathic thrombosis and protein-losing enteropathy (CHAPLE disease) is a lethal disease caused by genetic loss of the complement regulatory protein CD55, leading to overactivation of complement and innate immunity together with immunodeficiency due to immunoglobulin wasting in the intestine. We report in vivo human data accumulated using the complement C5 inhibitor eculizumab for the medical treatment of patients with CHAPLE disease. We observed cessation of gastrointestinal pathology together with restoration of normal immunity and metabolism. We found that patients rapidly renormalized immunoglobulin concentrations and other serum proteins as revealed by aptamer profiling, re-established a healthy gut microbiome, discontinued immunoglobulin replacement and other treatments and exhibited catch-up growth. Thus, we show that blockade of C5 by eculizumab effectively re-establishes regulation of the innate immune complement system to substantially reduce the pathophysiological manifestations of CD55 deficiency in humans.

Immunoglobulin E (IgE) is a key driver of type 1 hypersensitivity reactions and allergic disorders, which are globally increasing in number and severity. Although eliminating pathogenic IgE may be a powerful way to treat allergy, no therapeutic strategy reported to date can fully ablate IgE production. Interleukin-4 receptor α (IL-4Rα) signaling is required for IgE class switching, and IL-4Rα blockade gradually reduces, but does not eliminate, IgE. The persistence of IgE after IL-4Rα blockade may be due to long-lived IgE+plasma cells that maintain serological memory to allergens and thus may be susceptible to plasma cell–targeted therapeutics. We demonstrate that transient administration of a B cell maturation antigen x CD3 (BCMAxCD3) bispecific antibody markedly depletes IgE, as well as other immunoglobulins, by ablating long-lived plasma cells, although IgE and other immunoglobulins rapidly rebound after treatment. Concomitant IL-4Rα blockade specifically and durably prevents the reemergence of IgE by blocking IgE class switching while allowing the restoration of other immunoglobulins. Moreover, this combination treatment prevented anaphylaxis in mice. Together with additional cynomolgus monkey and human data, our studies demonstrate that allergic memory is primarily maintained by both non-IgE+memory B cells that require class switching and long-lived IgE+plasma cells. Our combination approach to durably eliminate pathogenic IgE has potential to benefit allergy in humans while preserving antibody-mediated immunity.

Background: Iron overload (IOL) develops in dyserythropoieses such as beta-thalassemia and myelodysplastic syndromes due both to red blood cell transfusions as well as inappropriate regulation of the hormone hepcidin, a key regulator of iron homeostasis. Hepcidin, produced in the liver, sequesters iron mainly in enterocytes and macrophages. In the setting of hepcidin down-regulation, toxic levels of labile iron can accumulate in organs such as the heart, liver, bone marrow, pancreas, and pituitary gland. The current standard-of-care for the treatment of IOL is iron chelation. Chelation solubilizes iron for renal excretion, but is associated with toxicities and limited patient satisfaction, severely limiting adoption and efficacy in certain disorders of IOL. There is a high unmet need for novel therapies which can safely reduce, and even prevent, toxic iron accumulation in organs in patients with IOL. Transmembrane serine protease 6 (TMPRSS6) is a membrane-bound serine protease whose expression is highly restricted to hepatocytes, where its only known role is inhibiting hepcidin transcription by cleaving the hemojuvelin co-receptor and thus reducing the bone morphogenetic protein (BMP) signaling pathway driving hepcidin production.

Notch signaling promotes T cell pathogenicity and graft-versus-host disease (GVHD) after allogeneic hematopoietic cell transplantation (allo-HCT) in mice, with a dominant role for the Delta-like Notch ligand DLL4. To assess whether Notch’s effects are evolutionarily conserved and to identify the mechanisms of Notch signaling inhibition, we studied antibody-mediated DLL4 blockade in a nonhuman primate (NHP) model similar to human allo-HCT. Short-term DLL4 blockade improved posttransplant survival with durable protection from gastrointestinal GVHD in particular. Unlike prior immunosuppressive strategies tested in the NHP GVHD model, anti-DLL4 interfered with a T cell transcriptional program associated with intestinal infiltration. In cross-species investigations, Notch inhibition decreased surface abundance of the gut-homing integrin α4β7 in conventional T cells while preserving α4β7 in regulatory T cells, with findings suggesting increased β1 competition for α4 binding in conventional T cells. Secondary lymphoid organ fibroblastic reticular cells emerged as the critical cellular source of Delta-like Notch ligands for Notch-mediated up-regulation of α4β7 integrin in T cells after allo-HCT. Together, DLL4-Notch blockade decreased effector T cell infiltration into the gut, with increased regulatory to conventional T cell ratios early after allo-HCT. Our results identify a conserved, biologically unique, and targetable role of DLL4-Notch signaling in intestinal GVHD.

Palmoplantar pustular psoriasis (PPPP) and non‒pustular palmoplantar psoriasis (NPPP) are localized, debilitating forms of psoriasis. The inflammatory circuits involved in PPPP and NPPP are not well-understood. To compare the cellular and immunological features that differentiate PPPP and NPPP, skin biopsies were collected from a total of 30 participants with PPPP, NPPP, and psoriasis vulgaris (PV) and from 10 healthy participants. A subset consented to a second biopsy after 3 additional weeks off medication. Histologic staining of lesional and nonlesional skin showed higher neutrophil counts in PPPP than in NPPP and PV and higher CD8+T-cell counts in NPPP. RNA sequencing and transcriptional analysis of skin biopsies showed enhanced IFN-γ pathway activation in NPPP lesions but stronger signatures of IL-17 pathway and neutrophil-related genes (e.g., IL36A) in PPPP lesional skin. Serum analysis on the Olink platform detected higher concentrations of T helper type 1, IFN-γ‒inducible chemokines in NPPP, and higher neutrophil-associated cytokines in PPPP. Taken together, this evidence suggests more pronounced T helper 1‒mediated inflammation in NPPP than in PV and PPPP and stronger neutrophil-associated activity in PPPP than in NPPP and PV. These data support targeting inflammatory pathways associated with neutrophilic inflammation (e.g., IL-36 signaling) for therapeutic development in PPPP.

CD40 ligand (CD40L) blockade has demonstrated efficacy in experimental autoimmune models. However, clinical trials of hu5c8, an anti-human CD40L IgG1antibody, in systemic lupus erythematosus (SLE) were halted due to an increased incidence of thrombotic events. This study evaluated CDP7657, a high affinity PEGylated monovalent Fab' anti-CD40L antibody fragment, to assess whether an Fc-deficient molecule retains efficacy while avoiding the increased risk of thrombotic events observed with hu5c8. The potency and cross-reactivity of CDP7657 was assessed in in vitroassays employing human and non-human primate leukocytes, and the capacity of different antibody formats to activate platelets in vitrowas assessed using aggregometry and dense granule release assays. Given the important role CD40L plays in regulating humoral immunity, in vivoefficacy was assessed by investigating the capacity of Cynomolgus monkeys to generate immune responses to the tetanus toxoid antigen while the potential to induce thrombotic events in vivowas evaluated after repeat dosing of antibodies to Rhesus monkeys. A PEGylated anti-mouse CD40L was generated to assess efficacy in the New Zealand Black/White (NZB/W) mouse model of SLE. CDP7657 dose-dependently inhibited antigen-specific immune responses to tetanus toxoid in Cynomolgus monkeys, and in contrast to hu5c8, there was no evidence of pulmonary thrombovasculopathy in Rhesus monkeys. Aglycosyl hu5c8, which lacks Fc receptor binding function, also failed to induce thrombotic events in Rhesus monkeys. In vitroexperiments confirmed that antibody constructs lacking an Fc, including CDP7657, did not induce human or monkey platelet activation. A PEGylated monovalent Fab' anti-mouse CD40L antibody also inhibited disease activity in the NZB/W mouse model of SLE after administration using a therapeutic dosing regimen where mice received antibodies only after they had displayed severe proteinuria. These findings demonstrate for the first time that anti-CD40L antibodies lacking a functional Fc region do not induce thrombotic events in Rhesus monkeys and fail to activate platelets in vitrobut, nevertheless retain pharmacological activity and support the investigation of CDP7657 as a potential therapy for systemic lupus erythematosus and other autoimmune diseases.

MHC class II molecules are expressed on the surface of antigen presenting cells and are loaded with peptides processed from the phagosomal compartment of these cells. Such complexes interact with the CD4 positive T lymphocyte receptor for antigen and a strong interaction is followed by T cell activation and proliferation. As class II expression is critical for antigen specific immunity its expression mostly restricted to a few cell types but can be induced on others in response to interferon . This expansion of antigen presenting ability plays a role in increasing the duration and intensity of the immune response. Nitric oxide and antioxidants attenuate this class II induction through negative effects on the induction of class II transactivator protein expression and on the binding of transcription factor NF-Y to the class II promoter.

INTRODUCTION

Introduction.Pozelimab (REGN3918) and cemdisiran (ALN-CC5) are C5 inhibitors under development for the treatment of paroxysmal nocturnal hemoglobinuria (PNH), myasthenia gravis (MG), and other diseases in which tissue damage is mediated by terminal complement pathway activity. Pozelimab is a fully human monoclonal immunoglobulin G4P (IgG4P) antibody directed against C5, and cemdisiran is a synthetic small interfering RNA (siRNA) targeting C5 mRNA. Both agents can be administered via subcutaneous (SC) injection. Pharmacokinetic (PK)/pharmacodynamic (PD) modeling based on observed data from both pozelimab and cemdisiran healthy volunteer studies (NCT03115996, NCT02352493) suggests that, by combining cemdisiran and pozelimab, the dose of both agents may be significantly reduced and the interval for SC dosing of pozelimab may be significantly increased.

Weyne: Regeneron Pharmaceuticals, Inc.: Current Employment, Current holder of stock options in a privately-held company. Chaudhari: Regeneron Pharmaceuticals, Inc.: Current Employment, Current holder of stock options in a privately-held company. Harari: Regeneron Pharmaceuticals, Inc.: Current Employment, Current holder of stock options in a privately-held company. Miller: Regeneron Pharmaceuticals, Inc.: Current Employment, Current holder of stock options in a privately-held company. Dain: Regeneron Pharmaceuticals, Inc.: Other: Contractor. Meagher: Regeneron Pharmaceuticals, Inc.: Current Employment, Current holder of stock options in a privately-held company. Rodgers: Regeneron Pharmaceuticals, Inc.: Current Employment, Current holder of stock options in a privately-held company. Perlee: Regeneron Pharmaceuticals, Inc.: Current Employment, Current holder of stock options in a privately-held company. Morton: Regeneron Pharmaceuticals, Inc.: Current Employment, Current holder of stock options in a privately-held company. Weinreich: Regeneron Pharmaceuticals, Inc.: Current Employment, Current holder of stock options in a privately-held company. Yancopoulos: Regeneron Pharmaceuticals, Inc.: Current Employment, Current holder of stock options in a privately-held company. Griffin: Alexion, AstraZeneca Rare Disease: Honoraria, Membership on an entity's Board of Directors or advisory committees; BioCryst Pharmaceuticals: Consultancy, Membership on an entity's Board of Directors or advisory committees; Sobi Pharmaceuticals: Honoraria, Membership on an entity's Board of Directors or advisory committees; Apellis: Other: Educational grant support.

van Zyl: Regeneron Pharmaceuticals, Inc.: Current Employment. Weyne: Regeneron Pharmaceuticals, Inc.: Current Employment, Current holder of stock options in a privately-held company. Chaudhari: Regeneron Pharmaceuticals, Inc.: Current Employment, Current holder of stock options in a privately-held company. Harari: Regeneron Pharmaceuticals, Inc.: Current Employment, Current holder of stock options in a privately-held company. Levy: Regeneron Pharmaceuticals, Inc.: Current Employment, Current holder of stock options in a privately-held company. Miller: Regeneron Pharmaceuticals, Inc.: Current Employment, Current holder of stock options in a privately-held company. Chen: Regeneron Pharmaceuticals, Inc.: Current Employment, Current holder of stock options in a privately-held company. Meagher: Regeneron Pharmaceuticals, Inc.: Current Employment, Current holder of stock options in a privately-held company. Rodgers: Regeneron Pharmaceuticals, Inc.: Current Employment, Current holder of stock options in a privately-held company. Perlee: Regeneron Pharmaceuticals, Inc.: Current Employment, Current holder of stock options in a privately-held company. Morton: Regeneron Pharmaceuticals, Inc.: Current Employment, Current holder of stock options in a privately-held company. Weinreich: Regeneron Pharmaceuticals, Inc.: Current Employment, Current holder of stock options in a privately-held company. Yancopoulos: Regeneron Pharmaceuticals, Inc.: Current Employment, Current holder of stock options in a privately-held company.

Devalaraja-Narashimha: Regeneron Pharmaceuticals, Inc.: Employment, Equity Ownership. Ni:Regeneron Pharmaceuticals, Inc.: Employment, Equity Ownership. Huang:Regeneron Pharmaceuticals, Inc.: Employment, Equity Ownership. Wang:Regeneron Pharmaceuticals, Inc.: Employment, Equity Ownership. Chaudhari:Regeneron Pharmaceuticals, Inc.: Employment, Equity Ownership. Prasad:Regeneron Pharmaceuticals, Inc.: Employment, Equity Ownership. Harari:Regeneron Pharmaceuticals, Inc.: Employment, Equity Ownership. Rankin:Regeneron Pharmaceuticals, Inc.: Employment, Equity Ownership. Morton:Regeneron Pharmaceuticals, Inc.: Employment, Equity Ownership. Weyne:Regeneron Pharmaceuticals, Inc.: Employment, Equity Ownership.The drug is pozelimab and it is a fully human anti-C5 IgG4 being tested a Phase 1 study in healthy volunteers.

INTRODUCTION:Blockade of complement factor C5 has demonstrated benefit in paroxysmal nocturnal hemoglobinuria, atypical hemolytic uremic syndrome, generalized myasthenia gravis and neuromyelitis optica. We have completed a Phase I study of pozelimab, a fully human anti-C5 IgG4, in healthy volunteers. Pozelimab was well tolerated and resulted in dose-dependent inhibition of hemolytic activity through the classical complement pathway in normal healthy volunteers. Complete inhibition of hemolytic activity was maintained over a 4-week dosing period by a weekly subcutaneous (SC) regimen following an intravenous (IV) loading dose (ASH2018 abstract).

The Notch signaling pathway is an evolutionarily conserved, cell-cell communication system with critical functions in organogenesis and tissue homeostasis, including hemato- and immuno-poiesis. Recent data have revealed important roles for Notch in the regulation of mature T cell differentiation and function. Studies in mouse models have identified Notch as a critical regulator of pathogenic T-cell responses during acute GVHD (aGVHD) (Zhang Y, 2011, Blood). However, the exact biological effects and the therapeutic potential of Notch pathway manipulation in clinical settings remains unclear.

Tkachev: Regeneron Pharmaceuticals, Inc.: Research Funding. Kuhnert:Regeneron Pharmaceuticals, Inc.: Employment. Blazar:Kadmon Corporation, LLC: Consultancy, Research Funding. Carpenter:Regeneron Pharmaceuticals, Inc.: Employment. Harari:Regeneron Pharmaceuticals, Inc.: Employment. Thurston:Regeneron Pharmaceuticals, Inc.: Employment, Equity Ownership. Kean:Regeneron Pharmaceuticals, Inc.: Research Funding.

Weyne: Regeneron Pharmaceuticals: Employment, Equity Ownership. Ni:Regeneron Pharmaceuticals: Employment, Equity Ownership. DelGizzi:Regeneron Pharmaceuticals: Employment, Equity Ownership. Godin:Regeneron Pharmaceuticals: Employment. Morton:Regeneron Pharmaceuticals: Employment, Equity Ownership. Prasad:Regeneron Pharmaceuticals: Employment, Equity Ownership. Rankin:Regeneron Pharmaceuticals: Employment, Equity Ownership. Simek-Lemos:Regeneron Pharmaceuticals: Employment, Equity Ownership. Wang:Regeneron Pharmaceuticals: Employment, Equity Ownership. Rippley:Regeneron Pharmaceuticals: Employment, Equity Ownership. Harari:Regeneron Pharmaceuticals, Inc.: Employment.

INTRODUCTION:Blockade of complement factor C5 has demonstrated benefit in Paroxysmal Nocturnal Hemoglobinuria (PNH), atypical Hemolytic Uremic Syndrome and Generalized Myasthenia Gravis. We developed a human IgG4P antibody, REGN3918, that binds with high affinity to wild-type and variant (R885H/C) human C5. REGN3918 was well-tolerated in monkey toxicology studies with up to 26 weeks of dosing at up to 100 mg/kg/week. This finding was supportive of conducting this first-in-human study of REGN3918 in healthy volunteers.

Our objective was to determine the interrelationships of interleukin (IL)-6 receptor inhibition with haemoglobin, acute-phase reactants and iron metabolism markers (including hepcidin) in patients with rheumatoid arthritis (RA).

Hu5c8, a whole IgG1 anti-CD40L antibody, is known to cause thrombotic side effects in patients with Systemic Lupus Erythematosus (SLE). Anti-CD40L-mediated activation of platelets in vitro was shown to be FcγRIIa-dependent1, suggesting that the adverse effects of hu5c8 could be due to this mechanism, and that anti-CD40L antibodies lacking a functional Fc region would not activate platelets. CDP7657 is a monovalent Fab' PEG anti-CD40L antibody being developed for the treatment of SLE. The aim of the present work was to study a range of anti-CD40L antibody formats in isolated platelet assays and to evaluate the role of the Fc region and of valency.Isolated human platelets from healthy donors were used in the platelet aggregometry and serotonin release assay systems. Antibodies were added either alone, or pre-complexed with soluble CD40L trimer (sCD40L) at optimal stoichiometry. Antibody IV.3 was used to block FcγRIIa. The antibodies and antibody fragments tested included hu5c8 in IgG1, aglycosyl IgG, Fab′, & (Fab′)2 formats, CDP7657, and the CDP7657 variable regions in di-Fab' PEG, tri-Fab' PEG and aglycosyl formats.Hu5c8 in complex with sCD40L caused strong aggregation (in 2–3 minutes) and >85% serotonin release, both alone and in complex with sCD40L. This activation was completely abrogated by blocking FcγRIIa. In contrast, platelet activation did not occur with CDP7657 or other antibody formats, in any assay, regardless of the valency or presence of sCD40L.The data support the hypothesis that platelet activation by anti-CD40L antibodies is dependent on the presence of an active Fc moiety, via interactions with FcγRIIa, and indicate that CDP7657 has the potential to deliver the therapeutic effect of anti-CD40L blockade in SLE without thrombotic toxicity. References:(1) Langer F et al. 2005; Thromb Haemost 93: 1137.Amirkhosravi: UCB: Research Funding.

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