High amounts of circulating interleukin (IL)-6 in the form of monomeric immune complexes during anti-IL-6 therapy. Towards a new methodology for measuring overall cytokine production in human in vivo

Nonclinical Investigation of Cytokine Mitigation Strategies for T-cell-Engaging Bispecifics in the Cynomolgus Macaque

SUMMARY

T-cell-directed cancer therapies such as T-cell-engaging bispecifics (TCBs) are commonly associated with cytokine release syndrome and associated clinical signs that can limit their tolerability and therapeutic benefit. Strategies for reducing cytokine release are therefore needed. Here, we report on studies performed in cynomolgus monkeys to test different approaches for mitigating cytokine release with TCBs. A "priming dose" as well as subcutaneous dosing reduced cytokine release compared with intravenous dosing but did not affect the intended T-cell response to the bispecific. As another strategy, cytokines or cytokine responses were blocked with an anti-IL-6 antibody, dexamethasone, or a JAK1/TYK2-selective inhibitor, and the effects on toxicity as well as T-cell responses to a TCB were evaluated. The JAK1/TYK2 inhibitor and dexamethasone prevented CRS-associated clinical signs on the day of TCB administration, but the anti-IL-6 had little effect. All interventions allowed for functional T-cell responses and expected damage to target-bearing tissues, but the JAK1/TYK2 inhibitor prevented the upregulation of activation markers on T cells, suggesting the potential for suppression of T-cell responses. Our results suggest that short-term prophylactic dexamethasone treatment may be an effective option for blocking cytokine responses without affecting desired T-cell responses to TCBs.

Targeting inflammation as cancer therapy

Inflammation has accompanied human beings since the emergence of wounds and infections. In the past decades, numerous efforts have been undertaken to explore the potential role of inflammation in cancer, from tumor development, invasion, and metastasis to the resistance of tumors to treatment. Inflammation-targeted agents not only demonstrate the potential to suppress cancer development, but also to improve the efficacy of other therapeutic modalities. In this review, we describe the highly dynamic and complex inflammatory tumor microenvironment, with discussion on key inflammation mediators in cancer including inflammatory cells, inflammatory cytokines, and their downstream intracellular pathways. In addition, we especially address the role of inflammation in cancer development and highlight the action mechanisms of inflammation-targeted therapies in antitumor response. Finally, we summarize the results from both preclinical and clinical studies up to date to illustrate the translation potential of inflammation-targeted therapies.

Engineering Anticytokine Antibodies for Immune Modulation

The delicate balance of immune homeostasis is regulated by the interactions between cytokines and their cognate cell surface signaling receptors. There is intensive interest in harnessing cytokines as drugs for diseases such as cancer and autoimmune disorders. However, the multifarious and often contradictory activities of cytokines, coupled with their short serum half-lives, limit clinical performance and result in dangerous toxicities. There is thus growing emphasis on manipulating natural cytokines to enhance their selectivity, safety, and durability through various strategies. One strategy that has gained traction in recent years is the development of anticytokine Abs that not only extend the circulation half-life of cytokines but also specifically bias their immune activities through multilayered molecular mechanisms. Although Abs are notorious for their antagonistic activities, this review focuses on anticytokine Abs that selectively agonize the activity of the target protein. This approach has potential to help realize the clinical promise of cytokine-based therapies.

Targeting IL-6 trans-signalling: past, present and future prospects

Interleukin-6 (IL-6) is a key immunomodulatory cytokine that affects the pathogenesis of diverse diseases, including autoimmune diseases, chronic inflammatory conditions and cancer. Classical IL-6 signalling involves the binding of IL-6 to the membrane-bound IL-6 receptor α-subunit (hereafter termed 'mIL-6R') and glycoprotein 130 (gp130) signal-transducing subunit. By contrast, in IL-6 trans-signalling, complexes of IL-6 and the soluble form of IL-6 receptor (sIL-6R) signal via membrane-bound gp130. A third mode of IL-6 signalling - known as cluster signalling - involves preformed complexes of membrane-bound IL-6-mIL-6R on one cell activating gp130 subunits on target cells. Antibodies and small molecules have been developed that block all three forms of IL-6 signalling, but in the past decade, IL-6 trans-signalling has emerged as the predominant pathway by which IL-6 promotes disease pathogenesis. The first selective inhibitor of IL-6 trans-signalling, sgp130, has shown therapeutic potential in various preclinical models of disease and olamkicept, a sgp130Fc variant, had promising results in phase II clinical studies for inflammatory bowel disease. Technological developments have already led to next-generation sgp130 variants with increased affinity and selectivity towards IL-6 trans-signalling, along with indirect strategies to block IL-6 trans-signalling. Here, we summarize our current understanding of the biological outcomes of IL-6-mediated signalling and the potential for targeting this pathway in the clinic.

Role of Interleukin-6 Family Cytokines in Organ Fibrosis

Background

Organ fibrosis remains an important cause of high incidence rate and mortality worldwide. The prominent role of interleukin-6 (IL-6) family members represented by IL-6 in inflammation has been extensively studied, and drugs targeting IL-6 have been used clinically. Because of the close relationship between inflammation and fibrosis, researches on the role of IL-6 family members in organ fibrosis are also gradually emerging.

Summary

In this review, we systematically reviewed the role of IL-6 family members in fibrosis and their possible mechanisms. We listed the role of IL-6 family members in organ fibrosis and drew two diagrams to illustrate the downstream signal transductions of IL-6 family members. We also summarized the effect of some IL-6 family members' antagonists in a table.

Key Messages

Fibrosis contributes to organ structure damage, organ dysfunction, and eventually organ failure. Although IL-6 family cytokines have similar downstream signal pathways, different members play various roles in an organ-specific manner which might be partly due to their different target cell populations. The pathogenic role of individual member in various diseases needs to be deciphered carefully.

Anti-interleukin-6 Antibody Clazakizumab in Antibody-mediated Renal Allograft Rejection: Accumulation of Antibody-neutralized Interleukin-6 Without Signs of Proinflammatory Rebound Phenomena

BACKGROUND

Blockade of interleukin-6 (IL-6) has emerged as a promising therapeutic option for antibody-mediated rejection. Subtherapeutic anti-IL-6 antibody level or treatment cessation following prolonged cytokine neutralization may result in proinflammatory rebound phenomena via accumulation of IL-6 and/or modulated gene expression of major components of the IL-6/IL-6 receptor (IL-6R) axis.

METHODS

We evaluated biologic material obtained from a randomized controlled, double-blind phase 2 trial designed to evaluate the safety and efficacy of the anti-IL-6 monoclonal antibody clazakizumab in late antibody-mediated rejection. Twenty kidney transplant recipients, allocated to clazakizumab or placebo, received 4-weekly doses over 12 wks, followed by a 40-wk extension where all recipients received clazakizumab. Serum proteins were detected using bead-based immunoassays and RNA transcripts using quantitative real-time polymerase chain reaction (peripheral blood) or microarray analysis (serial allograft biopsies).

RESULTS

Clazakizumab treatment resulted in a substantial increase in median total (bound and unbound to drug) serum IL-6 level (1.4, 8015, and 13 600 pg/mL at 0, 12, and 52 wks), but median level of free (unbound to drug) IL-6 did not increase (3.0, 2.3, and 2.3 pg/mL, respectively). Neutralization of IL-6 did not boost soluble IL-6R or leukocyte or allograft expression of IL-6, IL-6R, and glycoprotein 130 mRNA. Cessation of treatment at the end of the trial did not result in a meaningful increase in C-reactive protein or accelerated progression of graft dysfunction during 12 mo of follow-up.

CONCLUSION

Our results argue against clinically relevant rebound phenomena and modulation of major components of the IL-6/IL-6R axis following prolonged IL-6 neutralization with clazakizumab.

Pharmacokinetics, pharmacodynamics, safety, and immunogenicity of Gerilimzumab (GB224), a recombinant humanized interleukin-6 monoclonal antibody, in healthy Chinese adults: A randomized controlled dose-escalation study

OBJECTIVES

This study aimed to investigate the safety, pharmacokinetics (PK), pharmacodynamics (PD), and immunogenicity of Gerilimzumab (GB224), a recombinant humanized IgG1λ monoclonal antibody against interleukin-6, in healthy Chinese adults.

METHODS

Fifty-eight subjects were randomly assigned to receive a single subcutaneous dose of 2, 5, 10, 15, 20, 30 mg GB224 or placebo. Safety assessments were performed, and blood samples were collected for PK, PD, and immunogenicity analyses during a follow-up of 112 days.

RESULTS

The most frequent adverse event was decreased fibrinogen (43.1%). GB224 was absorbed relatively fast with a median T_max of 48 h (24-168 h) but eliminated slowly with a long mean half-life (839.38-981.63 h). Dose proportionality was shown to be in the dose range of 10-30 mg. A dose-dependent increase in serum interleukin-6 concentration from baseline was observed in the subjects receiving GB224. Only two subjects tested positive for antidrug antibodies after administration of GB224.

CONCLUSION

GB224 had a well-tolerated safety profile, desirable PK, and a low immunogenicity following a single-dose subcutaneous administration in healthy Chinese subjects. These findings warrant further investigation.

Restriction of interleukin-6 alters endothelial cell immunogenicity in an allogenic environment

The microvascular endothelium of the renal transplant is the first site of graft interaction with the host immune system and is often injured in chronic Antibody Mediated Rejection (AMR). Microvascular inflammation is an independent determinant of AMR and heightens endothelial expression of human leukocyte antigen (HLA) molecules thereby increasing the possibility of Donor Specific Antibody (DSA) binding. Endothelial cells (ECs) produce IL-6 in the steady-state that is increased by inflammation or by HLA-DR antibody binding in an allogeneic setting. Because IL-6 has been implicated in AMR, IL-6 blockade is currently under investigation as a therapeutic target. To further understand the role of IL-6 in EC immunogenicity, we have examined whether humanized antibody blockade of IL-6 altered EC interactions with allogeneic PBMC and after anti-HLA or DSA binding to ECs in an in vitro human experimental model. Soluble factors, endothelial phenotype, Stat-3 activation, CD4⁺ -T differentiation and C4d deposition were examined. Blockade of IL-6 reduced EC secretion of IL-6 and of the monocyte chemoattractant MCP-1. Pre-activation of ECs by anti-HLA or DSA binding increased IL-6 secretion, that was further increased by concurrent binding of both antibodies and this was inhibited by IL-6 blockade. Activation of Stat-3 in CD4⁺ -T mediated by soluble factors produced in endothelial-PBMC interactions, and endothelial differentiation of CD4⁺ -T cell subsets (Th1, Treg), were impaired whereas activation of Complement by anti-HLA antibody binding remained unchanged by IL-6 blockade. Together, these data identify EC-mediated pro-inflammatory responses (T cell expansion, EC auto-activation, chemokine secretion) targeted by IL-6 blockade.

IL-6 and its role in IgA nephropathy development

IL-6 is considered one of the well characterized cytokines exhibiting homeostatic, pro- and anti-inflammatory activities, depending on the receptor variant and the induced intracellular cis- or trans-signaling responses. IL-6-activated pathways are involved in the regulation of cell proliferation, survival, differentiation, and cell metabolism changes. Deviations in IL-6 levels or abnormal response to IL-6 signaling are associated with several autoimmune diseases including IgA nephropathy (IgAN), one of most frequent primary glomerulonephritis worldwide. IgAN is associated with increased plasma concentration of IL-6 and increased plasma concentration of aberrantly galactosylated IgA1 immunoglobulin (Gd-IgA1). Gd-IgA1 is specifically recognized by autoantibodies, leading to the formation of circulating immune complexes (CIC) with nephritogenic potential, since CIC deposited in the glomerular mesangium induce mesangial cells proliferation and glomerular injury. Infection of the upper respiratory or digestive tract enhances IL-6 production and in IgAN patients is often followed by the macroscopic hematuria. This review recapitulates general aspects of IL-6 signaling and summarizes experimental evidences about IL-6 involvement in the etiopathogenesis of IgA nephropathy through the production of Gd-IgA1 and regulation of mesangial cell proliferation.

Evaluation of Clazakizumab (anti-IL-6) in Patients with Treatment-Resistant Chronic Active Antibody Mediated Rejection of Kidney Allografts

Introduction

Interleukin-6 (IL-6) is an important mediator of inflammation and activation of T cells, B cells, and plasma cells. Excessive IL-6 production is linked to human diseases characterized by unregulated antibody production, including alloimmunity, where persistence of donor-specific antibodies (DSAs), chronic active antibody-mediated rejection (cAMR), and graft loss are noted. Here, we report our experience investigating clazakizumab, a novel IL-6 inhibitor, in treating human leukocyte antigen (HLA)-sensitized patients with cAMR.

Methods

Between February 2018 and January 2019, 10 adults with biopsy-proven cAMR were enrolled in a phase 2, single-center, open-label study. Patients received clazakizumab 25 mg subcutaneously (s.c.) monthly for 12 months, with a 6-month protocol biopsy. Primary end points included patient survival, graft survival, estimated glomerular filtration rate (eGFR), and safety. Secondary end points assessed immune markers (DSAs, IgG, T-regulatory [Treg] cells). At 12 months, stable patients entered a long-term extension (LTE).

Results

LTE patients received clazakizumab for >2.5 years. Mean eGFRs showed significant declines from −24 months to study initiation (0 months) (52.8 ± 14.6 to 38.11 ± 12.23 ml/min per 1.73 m², P = 0.03). However, after initiation of clazakizumab, eGFR stabilized at (41.6 ± 14.2 and 38.1 ± 20.3 ml/min per 1.73 m², at 12 and 24 months, respectively). Banff 2017 analysis of pre- and post-treatment biopsies showed reductions in g+ptc and C4d scores. DSA reductions were seen in most patients. Adverse events (AEs) were minimal, and 2 graft losses occurred, both in patients who discontinued clazakizumab therapy at 6 months and 12 months after study initiation.

Conclusion

In this small cohort of patients with cAMR, clazakizumab treatment showed a trend toward stabilization of eGFR and reductions in DSA and graft inflammation. No significant safety issues were observed. A randomized, placebo-controlled clinical trial (IMAGINE) of clazakizumab in cAMR treatment is underway (NCT03744910).

A Novel Humanized Anti-Interleukin-6 Antibody HZ0408b With Anti-Rheumatoid Arthritis Therapeutic Potential

Interleukin-6 (IL-6), a pleiotropic cytokine that regulates immune responses and inflammatory reactions, plays a pivotal role in the development of rheumatoid arthritis (RA). Blockade of IL-6 signaling with the monoclonal antibody (mAb) represents an important advancement in RA treatment. Although two IL-6 receptor antibodies are already available in the clinic, there is no mAb specifically targeting the human IL-6 to block IL-6 signaling for RA treatment. In this study, we have developed a novel humanized anti-IL-6 mAb HZ-0408b with potent binding and neutralizing activity to human IL-6. We demonstrated that HZ-0408b has a high species specificity and low cross-reactivity. Moreover, HZ-0408b showed a more potent inhibitory effect on IL-6 signaling than Siltuximab, an FDA-approved anti-IL-6 chimeric mAb. HZ-0408b is comparable to Olokizumab, a humanized mAb against IL-6 that is already in phase III studies. We observed that HZ-0408b is well tolerated at doses that can achieve therapeutic serum levels in cynomolgus monkey. Most importantly, we proved that HZ-0408b treatment significantly ameliorated joint swelling after the onset of arthritis and dramatically reduced plasma C-reactive protein (CRP) levels in a monkey collagen-induced arthritis (CIA) model. Collectively, our findings using non-human primates indicate that humanized anti-IL-6 mAb HZ-0408b has excellent safety and efficacy profiles for RA therapy.

Anti-Interleukin 6 Therapeutics for Chronic Antibody-Mediated Rejection In Kidney Transplant Recipients

Chronic antibody-mediated rejection is the predominant cause for late renal allograft loss for which there is, as yet, no treatment approved by the US Food and Drug Administration, although there are clinical trials in progress to evaluate novel treatment strategies. The current standard of care treatment is based on expert consensus, rather than scientific evidence, and includes glucocorticoids, plasma exchange, and intravenous immunoglobulin, with or without rituximab or bortezomib. The low success rate with presently established management protocols represents a conspicuous exigency in the field of kidney transplantation. This review focuses on the biologic basis for interleukin 6 inhibitors, specifically tocilizumab and clazakizumab, and the safety and efficacy profiles of these agents for treatment of chronic antibodymediated rejection in kidney transplant recipients.

Unravelling the broader complexity of IL-6 involvement in health and disease

The classification of interleukin-6 (IL-6) as a pro-inflammatory cytokine undervalues the biological impact of this cytokine in health and disease. With broad activities affecting the immune system, tissue homeostasis and metabolic processes, IL-6 displays complex biology. The significance of these involvements has become increasingly important in clinical settings where IL-6 is identified as a prominent target for therapy. Here, clinical experience with IL-6 antagonists emphasises the need to understand the context-dependent properties of IL-6 within an inflammatory environment and the anticipated or unexpected consequences of IL-6 blockade. In this review, we will describe the immunobiology of IL-6 and explore the gamut of IL-6 bioactivity affecting the clinical response to biological drugs targeting this cytokine pathway.

Bazedoxifene, a GP130 Inhibitor, Modulates EMT Signaling and Exhibits Antitumor Effects in HPV-Positive Cervical Cancer

Persistent HPV (Human Papillomavirus) infection is the primary cause of cervical cancer. Despite the development of the HPV vaccine to prevent infections, cervical cancer is still a fatal malignant tumor and metastatic disease, and it is often difficult to treat, so a new treatment strategy is needed. The FDA-approved drug Bazedoxifene is a novel inhibitor of protein–protein interactions between IL-6 and GP130. Multiple ligand simultaneous docking and drug repositioning approaches have demonstrated that an IL-6/GP130 inhibitor can act as a selective estrogen modulator. However, the molecular basis for GP130 activation in cervical cancer remains unclear. In this study, we investigated the anticancer properties of Bazedoxifene in HPV-positive cervical cancer cells. In vitro and in vivo experiments showed that Bazedoxifene inhibited cell invasion, migration, colony formation, and tumor growth in cervical cancer cells. We also confirmed that Bazedoxifene inhibits the GP130/STAT3 pathway and suppresses the EMT (Epithelial-mesenchymal transition) sub-signal. Thus, these data not only suggest a molecular mechanism by which the GP130/STAT3 pathway may promote cancer, but also may provide a basis for cervical cancer replacement therapy.

Anti-interleukin-6 antibody clazakizumab in late antibody-mediated kidney transplant rejection: effect on cytochrome P450 drug metabolism

Targeting interleukin-6 (IL-6) is a promising strategy to counteract antibody-mediated rejection (ABMR). In inflammatory states, IL-6 antagonism was shown to modulate cytochrome P450 (CYP), but its impact on drug metabolism in ABMR treatment was not addressed so far. We report a sub-study of a phase 2 trial of anti-IL-6 antibody clazakizumab in late ABMR (ClinicalTrials.gov, NCT03444103). Twenty kidney transplant recipients were randomized to clazakizumab versus placebo (4-weekly doses; 12 weeks), followed by a 9-month extension where all recipients received clazakizumab. To study CYP2C19/CYP3A4 metabolism, we administered pantoprazole (20 mg intravenously) at prespecified time points. Dose-adjusted C₀ levels (C₀ /D ratio) of tacrolimus (n = 13) and cyclosporin A (CyA, n = 6) were monitored at 4-weekly intervals. IL-6 and C-reactive protein were not elevated at baseline, the latter was then suppressed to undetectable levels under clazakizumab. IL-6 blockade had no clinically meaningful impact on pantoprazole pharmacokinetics (area under the curve; baseline versus week 52: 3.16 [2.21-7.84] versus 4.22 [1.99-8.18] μg/ml*h, P = 0.36) or calcineurin inhibitor C₀ /D ratios (tacrolimus: 1.49 [1.17-3.20] versus 1.37 [0.98-2.42] ng/ml/mg, P = 0.21; CyA: 0.69 [0.57-0.85] versus 1.08 [0.52-1.38] ng/ml/mg, P = 0.47). We conclude that IL-6 blockade in ABMR - in absence of systemic inflammation - may have no meaningful effect on CYP metabolism.

Endosomes as Signaling Platforms for IL-6 Family Cytokine Receptors

Interleukin-6 (IL-6) is the name-giving cytokine of a family of eleven members, including IL-6, CNTF, LIF, and IL-27. IL-6 was first recognized as a B-cell stimulating factor but we now know that the cytokine plays a pivotal role in the orchestration of inflammatory processes as well as in inflammation associated cancer. Moreover, IL-6 is involved in metabolic regulation and it has been shown to be involved in major neural activities such as neuroprotection, which can help to repair and to reduce brain damage. Receptor complexes of all members formed at the plasma membrane contain one or two molecules of the signaling receptor subunit GP130 and the mechanisms of signal transduction are well understood. IL-6 type cytokines can also signal from endomembranes, in particular the endosome, and situations have been reported in which endocytosis of receptor complexes are a prerequisite of intracellular signaling. Moreover, pathogenic GP130 variants were shown to interfere with spatial activation of downstream signals. We here summarize the molecular mechanisms underlying spatial regulation of IL-6 family cytokine signaling and discuss its relevance for pathogenic processes.

Therapeutic targeting of IL-6 trans-signaling

Interleukin-6 (IL-6) is a cytokine, which is involved in innate and acquired immunity, in neural cell maintenance and in metabolism. IL-6 can be synthesized by many different cells including myeloid cells, fibroblasts, endothelial cells and lymphocytes. The synthesis of IL-6 is strongly stimulated by Toll like receptors and by IL-1. Therefore, IL-6 levels in the body are high during infection and inflammatory processes. Moreover, IL-6 is a prominent growth factor of tumor cells and plays a major role in inflammation associated cancer. On target cells, IL-6 binds to an IL-6 receptor, which is not signaling competent. The complex of IL-6 and IL-6 receptor associate with a second receptor subunit, glycoprotein gp130, which dimerizes and initiates intracellular signaling. Cells, which do not express the IL-6 receptor are not responsive to IL-6. They can, however, be stimulated by the complex of IL-6 and a soluble form of the IL-6 receptor, which is generated by limited proteolysis and to a lesser extent by translation from an alternatively spliced mRNA. This process has been named IL-6 trans-signaling. This review article will explain the biology of IL-6 trans-signaling and the specific inhibition of this mode of signaling, which has been recognized to be fundamental in inflammation and cancer.

Androgen Receptor-Dependent Mechanisms Mediating Drug Resistance in Prostate Cancer

Androgen receptor (AR) is a main driver of prostate cancer (PCa) growth and progression as well as the key drug target. Appropriate PCa treatments differ depending on the stage of cancer at diagnosis. Although androgen deprivation therapy (ADT) of PCa is initially effective, eventually tumors develop resistance to the drug within 2-3 years of treatment onset leading to castration resistant PCa (CRPC). Castration resistance is usually mediated by reactivation of AR signaling. Eventually, PCa develops additional resistance towards treatment with AR antagonists that occur regularly, also mostly due to bypass mechanisms that activate AR signaling. This tumor evolution with selection upon therapy is presumably based on a high degree of tumor heterogenicity and plasticity that allows PCa cells to proliferate and develop adaptive signaling to the treatment and evolve pathways in therapy resistance, including resistance to chemotherapy. The therapy-resistant PCa phenotype is associated with more aggressiveness and increased metastatic ability. By far, drug resistance remains a major cause of PCa treatment failure and lethality. In this review, various acquired and intrinsic mechanisms that are AR‑dependent and contribute to PCa drug resistance will be discussed.

Historical overview of the interleukin-6 family cytokine

Interleukin-6 (IL-6) has been identified as a 26-kD secreted protein that stimulates B cells to produce antibodies. Later, IL-6 was revealed to have various functions that overlap with other IL-6 family cytokines and use the common IL-6 signal transducer gp130. IL-6 stimulates cells through multiple pathways, using both membrane and soluble IL-6 receptors. As indicated by the expanding market for IL-6 inhibitors, it has become a primary therapeutic target among IL-6 family cytokines. Here, we revisit the discovery of IL-6; discuss insights regarding the roles of this family of cytokines; and highlight recent advances in our understanding of regulation of IL-6 expression.

Lack of Interleukin-6 Affects IFN-γ and TNF-α Production and Early In Vivo Control of Brucella abortus Infection

Interleukin-6 (IL-6) is a pleiotropic cytokine promptly produced in response to infections, which contributes to host defense through the stimulation of acute phase immune responses. Brucella abortus is an intracellular bacterium that causes chronic disease in humans and domestic animals and triggers a robust immune response, characterized by the production of inflammatory cytokines. However, the mechanisms of IL-6-related immune responses in the context of Brucella infections are not completely understood. In this report, we describe an increased susceptibility of IL-6 knockout (KO) mice in the early phase of Brucella infection. Furthermore, we demonstrate that IL-6 is required for interferon (IFN)-γ and tumor necrosis factor (TNF)-α induction by infected splenocytes, indicating a protective role for IL-6 against B. abortus that parallels with Th1 type of immune response. Additionally, IL-6 KO mice exhibited reduced splenomegaly during the early phase of the infection. Corroborating this result, IL-6 KO mice displayed reduced numbers of macrophages, dendritic cells, and neutrophils in the spleen and reduced myeloperoxidase activity in the liver compared to wild-type infected mice. However, we demonstrate that IL-6 is not involved in B. abortus intracellular restriction in mouse macrophages. Taken together, our findings demonstrate that IL-6 contributes to host resistance during the early phase of B. abortus infection in vivo, and suggest that its protective role maybe partially mediated by proinflammatory immune responses and immune cell recruitment.

MAP kinase phosphatase-1, a gatekeeper of the acute innate immune response

Mitogen-activated protein kinase (MAPK)^§ cascades are crucial signaling pathways in the regulation of the host immune response to infection. MAPK phosphatase (MKP)-1, an archetypal member of the MKP family, plays a pivotal role in the down-regulation of p38 and JNK. Studies using cultured macrophages have demonstrated a pivotal role of MKP-1 in the restraint of the biosynthesis of both pro-inflammatory and anti-inflammatory cytokines as well as chemokines. Using MKP-1 knockout mice, several groups have not only confirmed the critical importance of MKP-1 in the regulation of the cytokine synthesis in vivo during the acute host response to bacterial infections, but also revealed novel functions of MKP-1 in maintaining bactericidal functions and host metabolic activities. RNA-seq analyses on livers of septic mice infected with E. coli have revealed that MKP-1 deficiency caused substantial perturbation in the expression of over 5000 genes, an impressive >20% of the entire murine genome. Among the genes whose expression are dramatically affected by MKP-1 deficiency are those encoding metabolic regulators and acute phase response proteins. These studies demonstrate that MKP-1 is an essential gate-keeper of the acute innate immune response, facilitating pathogen killing and regulating the metabolic response during pathogenic infection. In this review article, we will summarize the studies on the function of MKP-1 during acute innate immune response in the regulation of inflammation, metabolism, and acute phase response. We will also discuss the role of MKP-1 in the actions of numerous immunomodulatory agents.

Prediction of clinical effects of infliximab administered for inflammatory bowel disease based on pharmacokinetic and pharmacodynamic modeling

Infliximab (IFX) is used as a therapeutic agent for ulcerative colitis (UC) and Crohn's disease (CD). Although the dosage regimen has been established through clinical trial experience, it has yet to be assessed with a pharmacokinetic and pharmacodynamic model. The present study analysed sequential changes of clinical response in patients with ulcerative colitis and Crohn's disease following repeated administrations of infliximab using the pharmacokinetic/pharmacodynamic model. In addition, the dosage regimen presently used for patients with ulcerative colitis was evaluated, as well as the potential efficacy gained by increasing the dose and/or reducing the interval of administration for patients with Crohn's disease. Furthermore, the possibility of evaluating the difference between both diseases with regard to the efficacy of infliximab was investigated. Sequential changes in the clinical response values obtained with our model were in good agreement with the observed values following administration of infliximab in patients with ulcerative colitis and Crohn's disease. The results showed the importance of a loading dose for patients with ulcerative colitis, as well as the efficacy of increasing the dose and reducing the interval for patients with Crohn's disease. Also, the efficacy of infliximab for both diseases is suggested to be similar. In conclusion, our results show a possible modeling scenario that can accommodate the clinical response to infliximab administered for ulcerative colitis and Crohn's disease. Furthermore, it provides confirmation for the present dosage regimens given for these diseases.

Granulocyte-macrophage colony-stimulating factor (GM-CSF) as a therapeutic target in psoriasis: randomized, controlled investigation using namilumab, a specific human anti-GM-CSF monoclonal antibody

BACKGROUND

The relevance of granulocyte-macrophage colony-stimulating factor (GM-CSF) in the management of psoriasis has not been studied previously. GM-CSF is important in the initiation and maintenance of chronic inflammatory processes.

OBJECTIVES

To investigate the clinical use of GM-CSF neutralization by evaluating the efficacy and safety of namilumab (AMG203), a monoclonal antibody GM-CSF inhibitor, in patients with moderate-to-severe plaque psoriasis.

METHODS

A phase II, multicentre, randomized, double-blind, placebo-controlled, parallel-group, dose-finding, proof-of-concept study (NEPTUNE) was conducted. Four doses of namilumab (20, 50, 80 and 150 mg, via subcutaneous injection) were compared with placebo. Assessment of the primary end point - the proportion of patients achieving ≥ 75% reduction in Psoriasis Area and Severity Index (PASI 75 treatment response) - was performed at week 12. Exploratory investigation at the tissue level was conducted in a subset of the overall study population. The trial was registered with the number NCT02129777.

RESULTS

In total, 122 patients were enrolled and 106 (86·9%) completed the double-blind treatment; 16 (13·1%) prematurely discontinued study medication. Serum concentration-time profiles were as expected for subcutaneous delivery of an IgG1 monoclonal antibody, and exposure increased proportionally with dose elevation. The number of patients showing PASI 75 treatment response at week 12 was low in all groups; no significant difference was recorded in this end point between placebo and any namilumab group. Similar outcomes were recorded for other clinical study end points. Moreover, no significant treatment-related changes from baseline were observed in laboratory investigations of cell types or subpopulations, or cytokines relevant to inflammatory pathways in psoriasis.

CONCLUSIONS

GM-CSF blockade is not critical for suppression of key inflammatory pathways underlying psoriasis.

Interleukin-6: designing specific therapeutics for a complex cytokine

Interleukin-6 (IL-6) is a pivotal cytokine with a diverse repertoire of physiological functions that include regulation of immune cell proliferation and differentiation. Dysregulation of IL-6 signalling is associated with inflammatory and lymphoproliferative disorders such as rheumatoid arthritis and Castleman disease, and several classes of therapeutics have been developed that target components of the IL-6 signalling pathway. So far, monoclonal antibodies against IL-6 or IL-6 receptor (IL-6R) and Janus kinases (JAK) inhibitors have been successfully developed for the treatment of autoimmune diseases such as rheumatoid arthritis. However, clinical trials of agents targeting IL-6 signalling have also raised questions about the diseases and patient populations for which such agents have an appropriate benefit-risk profile. Knowledge from clinical trials and advances in our understanding of the complexities of IL-6 signalling, including the potential to target an IL-6 trans-signalling pathway, are now indicating novel opportunities for therapeutic intervention. In this Review, we overview the roles of IL-6 in health and disease and analyse progress with several approaches of inhibiting IL-6-signalling, with the aim of illuminating when and how to apply IL-6 blockade.

Smoking and pre-existing organ damage reduce the efficacy of belimumab in systemic lupus erythematosus

OBJECTIVES

Belimumab is the first biologic drug approved for Systemic Lupus Erythematosus (SLE). Here, we aimed to investigate the effects of belimumab on clinical and serologic outcomes, and sought to identify predictors of treatment response in three Swedish real-life settings.

METHODS

Fifty-eight patients were enrolled at initiation of belimumab and followed longitudinally for up to 53months. Surveillance outcomes included the SLE Disease Activity Index 2000 (SLEDAI-2K), 100mm Visual Analogue Scales for Physician's Global Assessment (PGA), fatigue, pain and general health, and the Systemic Lupus International Collaborating Clinics/American College of Rheumatology Damage Index (SDI). Assessment of treatment response included the SLE responder index (SRI). B lymphocyte stimulator (BLyS) levels were determined using ELISA.

RESULTS

SLEDAI-2K (median baseline score: 8.0; IQR: 4.0-13.8), PGA and corticosteroid use decreased during therapy, and patients reported improvements on fatigue, pain, and general health (p<0.0001 for all). SDI scores remained stable (p=0.08). Patients with baseline SDI scores >1 showed decreased probability and prolonged time to attain SRI response (HR: 0.449; 95% CI: 0.208-0.967), as did current smokers compared with non-smokers (HR: 0.103; 95% CI: 0.025-0.427). In contrast, baseline BLyS levels ≥1.2ng/mL predicted increased probability and shorter time to attain SRI response (HR: 2.566; 95% CI: 1.222-5.387).

CONCLUSIONS

Disease activity and corticosteroid usage decreased, patient-reported outcomes improved, and no significant organ damage was accrued during follow-up. Smoking and organ damage predicted reduced treatment efficacy. These findings might contribute to a better selection of patients who are likely to benefit from belimumab.

Bazedoxifene as a Novel GP130 Inhibitor for Pancreatic Cancer Therapy

The IL6/GP130/STAT3 pathway is crucial for tumorigenesis in multiple cancer types, including pancreatic cancer, and presents as a viable target for cancer therapy. We reported Bazedoxifene, which is approved as a selective estrogen modulator by FDA, as a novel inhibitor of IL6/GP130 protein-protein interactions using multiple ligand simultaneous docking and drug repositioning approaches. STAT3 is one of the major downstream effectors of IL6/GP130. Here, we observed Bazedoxifene inhibited STAT3 phosphorylation and STAT3 DNA binding, induced apoptosis, and suppressed tumor growth in pancreatic cancer cells with persistent IL6/GP130/STAT3 signaling in vitro and in vivo In addition, IL6, but not INFγ, rescued Bazedoxifene-mediated reduction of cell viability. Bazedoxifene also inhibited STAT3 phosphorylation induced by IL6 and IL11, but not by OSM or STAT1 phosphorylation induced by INFγ in pancreatic cancer cells, suggesting that Bazedoxifene inhibits the GP130/STAT3 pathway mediated by IL6 and IL11. Furthermore, Bazedoxifene combined with paclitaxel or gemcitabine synergistically inhibited cell viability and cell migration in pancreatic cancer cells. These results indicate that Bazedoxifene is a potential agent and can generate synergism when combined with conventional chemotherapy in human pancreatic cancer cells and tumor xenograft in mice. Therefore, our results support that Bazedoxifene as a novel inhibitor of GP130 signaling and may be a potential and safe therapeutic agent for human pancreatic cancer therapy. Mol Cancer Ther; 15(11); 2609-19. ©2016 AACR.

IL-6 pathway in the liver: From physiopathology to therapy

Interleukin 6 (IL-6) is a pleiotropic four-helix-bundle cytokine that exerts multiple functions in the body. In the liver, IL-6 is an important inducer of the acute phase response and infection defense. IL-6 is furthermore crucial for hepatocyte homeostasis and is a potent hepatocyte mitogen. It is not only implicated in liver regeneration, but also in metabolic function of the liver. However, persistent activation of the IL-6 signaling pathway is detrimental to the liver and might ultimately result in the development of liver tumors. On target cells IL-6 can bind to the signal transducing subunit gp130 either in complex with the membrane-bound or with the soluble IL-6 receptor to induce intracellular signaling. In this review we describe how these different pathways are involved in the physiology and pathophyiology of the liver. We furthermore discuss how IL-6 pathways can be selectively inhibited and therapeutically exploited for the treatment of liver pathologies.

The role of interleukin-6 signaling in nervous tissue

The cytokine interleukin-6 (IL-6) plays a critical role in the pathogenesis of inflammatory disorders and in the physiological homeostasis of neural tissue. Profound neuropathological changes, such as multiple sclerosis (MS), Parkinson's and Alzheimer's disease are associated with increased IL-6 expression in brain. Increased nocturnal concentrations of serum IL-6 are found in patients with impaired sleep whereas IL-6-deficient mice spend more time in rapid eye movement sleep associated with dreaming. IL-6 is crucial in the differentiation of oligodendrocytes, regeneration of peripheral nerves and acts as a neurotrophic factor. It exerts its cellular effects through two distinct pathways which include the anti-inflammatory pathway involving the membrane-bound IL-6 receptor (IL-6R) expressed on selective cells, including microglia, in a process known as classical signaling that is also critical for bacterial defense. In classical signaling binding of IL-6 to the membrane-bound IL-6R activates the β-receptor glycoprotein 130 (gp130) and subsequent down-stream signaling. The alternative, rather pro-inflammatory pathway, shown to mediate neurodegeneration in mice, termed trans-signaling, depends on a soluble form of the IL-6R that is capable of binding IL-6 to stimulate a response on distal cells that express gp130. A naturally occurring soluble form of gp130 (sgp130) has been identified that can specifically bind and neutralize the IL-6R/IL-6 complex. Thus, trans-signaling is blocked but classical signaling is completely unaffected. A modified, recombinant dimerized version of sgp130 (sgp130Fc) has successfully been used to block inflammatory processes in mice and may also be used in the clarification of IL-6 trans-signaling in neurological diseases.

From the bench to clinical practice: understanding the challenges and uncertainties in immunogenicity testing for biopharmaceuticals

Unlike conventional chemical drugs where immunogenicity typically does not occur, the development of anti-drug antibodies following treatment with biologics has led to concerns about their impact on clinical safety and efficacy. Hence the elucidation of the immunogenicity of biologics is required for drug approval by health regulatory authorities worldwide. Published ADA 'incidence' rates can vary greatly between same-class products and different patient populations. Such differences are due to disparate bioanalytical methods and interpretation approaches, as well as a plethora of product-specific and patient-specific factors that are not fully understood. Therefore, the incidence of ADA and their association with clinical consequences cannot be generalized across products. In this context, the intent of this review article is to discuss the complex nature of ADA and key nuances of the methodologies used for immunogenicity assessments, and to dispel some fallacies and myths.

A Novel Small-Molecule Inhibitor Targeting the IL-6 Receptor β Subunit, Glycoprotein 130

IL-6 is a major causative factor of inflammatory disease. Although IL-6 and its signaling pathways are promising targets, orally available small-molecule drugs specific for IL-6 have not been developed. To discover IL-6 antagonists, we screened our in-house chemical library and identified LMT-28, a novel synthetic compound, as a candidate IL-6 blocker. The activity, mechanism of action, and direct molecular target of LMT-28 were investigated. A reporter gene assay showed that LMT-28 suppressed activation of STAT3 induced by IL-6, but not activation induced by leukemia inhibitory factor. In addition, LMT-28 downregulated IL-6-stimulated phosphorylation of STAT3, gp130, and JAK2 protein and substantially inhibited IL-6-dependent TF-1 cell proliferation. LMT-28 antagonized IL-6-induced TNF-α production in vivo. In pathologic models, oral administration of LMT-28 alleviated collagen-induced arthritis and acute pancreatitis in mice. Based on the observation of upstream IL-6 signal inhibition by LMT-28, we hypothesized IL-6, IL-6Rα, or gp130 to be putative molecular targets. We subsequently demonstrated direct interaction of LMT-28 with gp130 and specific reduction of IL-6/IL-6Rα complex binding to gp130 in the presence of LMT-28, which was measured by surface plasmon resonance analysis. Taken together, our data suggest that LMT-28 is a novel synthetic IL-6 inhibitor that functions through direct binding to gp130.

Interleukin-6 as a therapeutic target

Human IL6 is a cytokine produced by many cell types that has pleiotropic effects. In agreement, anti-IL6 therapy reduces inflammation, hepatic acute phase proteins, and anemia and has antiangiogenic effects. Blocking IL6 has demonstrated therapeutic efficacy with drug registration in Castleman disease and inflammatory diseases (rheumatoid arthritis) without major toxicity. Interestingly, the inhibition of C-reactive protein (CRP) production is a trustworthy surrogate marker of anti-IL6 therapy efficacy. Clinically registered IL6 inhibitors include siltuximab, an anti-IL6 mAb, and tocilizumab, an anti-IL6R mAb. In various cancers, in particular plasma cell cancers, large randomized trials showed no efficacy of IL6 inhibitors, despite a full inhibition of CRP production in treated patients in vivo, the numerous data showing an involvement of IL6 in these diseases, and initial short-term treatments demonstrating a dramatic inhibition of cancer cell proliferation in vivo. A likely explanation is the plasticity of cancer cells, with the presence of various subclones, making the outgrowth of cancer subclones possible using growth factors other than IL6. In addition, current therapeutic strategies used in these cancers already target IL6 activity. Thus, anti-IL6 therapeutics are able to neutralize IL6 production in vivo and are safe and useful in inflammatory diseases and Castleman disease.

The Th17 pathway as a therapeutic target in rheumatoid arthritis and other autoimmune and inflammatory disorders

Production of the pro-inflammatory cytokine interleukin (IL)-17 by Th17 cells and other cells of the immune system protects the host against bacterial and fungal infections, but also promotes the development of rheumatoid arthritis (RA) and other autoimmune and inflammatory disorders. Several biologicals targeting IL-17, the IL-17 receptor, or IL-17-related pathways are being tested in clinical trials, and might ultimately lead to better treatment for patients suffering from various IL-17-mediated disorders. In this review, we provide a clear overview of current knowledge on Th17 cell regulation and the main Th17 effector cytokines in relation to IL-17-mediated conditions, as well as on recent IL-17-related drug developments. We demonstrate that targeting the Th17 pathway is a promising treatment for rheumatoid arthritis and various other autoimmune and inflammatory diseases. However, improvements in technical developments assisting in the identification of patients suffering from IL-17-driven disease are needed to enable the application of tailor-made, personalized medicine.

A high-affinity protein binder that blocks the IL-6/STAT3 signaling pathway effectively suppresses non-small cell lung cancer

Interleukin-6 (IL-6) is a multifunctional cytokine that regulates immune responses for host defense and tumorigenic process. Upregulation of IL-6 is known to constitutively phosphorylate signal transducer and activator of transcription 3 (STAT3), leading to activation of multiple oncogene pathways and inflammatory cascade. Here, we present the development of a high-affinity protein binder, termed repebody, which effectively suppresses non-small cell lung cancer in vivo by blocking the IL-6/STAT3 signaling. We selected a repebody that prevents human IL-6 (hIL-6) from binding to its receptor by a competitive immunoassay, and modulated its binding affinity for hIL-6 up to a picomolar range by a modular approach that mimics the combinatorial assembly of diverse modules to form antigen-specific receptors in nature. The resulting repebody was highly specific for hIL-6, effectively inhibiting the STAT3 phosphorylation in a dose- and binding affinity-response manner in vitro. The repebody was shown to have a remarkable suppression effect on the growth of tumors and STAT3 phosphorylation in xenograft mice with non-small cell lung cancer by blocking the hIL-6/STAT3 signaling. Structural analysis of the repebody and IL-6 complex revealed that the repebody binds the site 2a of hIL-6, overlapping a number of epitope residues at site 2a with gp130, and consequently causes a steric hindrance to the formation of IL-6/IL-6Rα complex. Our results suggest that high-affinity repebody targeting the IL-6/STAT3 pathway can be developed as therapeutics for non-small cell lung cancer.

Clinical experience of IL-6 blockade in rheumatic diseases - implications on IL-6 biology and disease pathogenesis

Interleukin 6 (IL-6) plays a significant role in many rheumatological diseases and has been described as both a pro- and anti-inflammatory cytokine. IL-6 blockade has been investigated in various rheumatic diseases and a humanised anti-IL-6 receptor antibody has been licensed for use in rheumatoid arthritis, systemic and polyarticular juvenile idiopathic arthritis. The increasing clinical experience of IL-6 blockade in rheumatic diseases adds to the existing knowledge regarding the physiological and pathological roles of IL-6.

Current understanding of rheumatoid arthritis therapy

Progress in understanding the cellular and molecular mechanisms of rheumatoid arthritis (RA), together with the availability of new therapies, has changed the way we think about RA. The paradigm shift in RA therapy has been from controlling symptoms to controlling the disease process with the abrogation of inflammation. Challenges that are still unresolved include the issues in disease prevention, treatment specificity to restore tolerance, approaches to facilitate tissue repair, and treatment optimization to fit the individual patient's disease phenotype and comorbidity context. This review summarizes the pathogenesis-related rationales for the current therapeutic strategies in RA and for emerging therapies and potential approaches to restoring immune tolerance in RA.

Therapeutic strategies for the clinical blockade of IL-6/gp130 signaling

The successful treatment of certain autoimmune conditions with the humanized anti-IL-6 receptor (IL-6R) antibody tocilizumab has emphasized the clinical importance of cytokines that signal through the β-receptor subunit glycoprotein 130 (gp130). In this Review, we explore how gp130 signaling controls disease progression and examine why IL-6 has a special role among these cytokines as an inflammatory regulator. Attention will be given to the role of the soluble IL-6R, and we will provide a perspective into the clinical blockade of IL-6 activity in autoimmunity, inflammation, and cancer.

Increased inflammation and impaired resistance to Chlamydophila pneumoniae infection in Dusp1(-/-) mice: critical role of IL-6

The MAPK phosphatase DUSP1 is an essential negative regulator of TLR-triggered innate immune activation. Here, we have investigated the impact of DUSP1 on inflammatory and antimicrobial host responses to the intracellular pathogen Chlamydophila pneumoniae. Following nasal infection, DUSP1-deficient mice mounted an enhanced pulmonary cytokine (IL-1beta, IL-6) and chemokine response (CCL3, CCL4, CXCL1, CXCL2), leading to increased leukocyte infiltration. Of interest, the increased inflammatory response, in the absence of DUSP1, was associated with higher bacterial numbers in the lungs, although the expression of IFN-gamma and critical antichlamydial effector molecules, such as iNOS, was intact. Blockade of IL-6 trans-signaling by injection of a soluble gp130-Fc fusion protein corrected the overshooting chemokine production as well as the increased chlamydial load in Dusp1(-/-) mice. Furthermore, IL-6 enhanced the replication of C. pneumoniae in embryonic fibroblasts in vitro. These data show that DUSP1 is required to achieve a balanced response to chlamydial infection and identify IL-6 as critical for amplifying inflammation and benefiting chlamydial growth through direct effects on infected cells.

Impact of interleukin-6 classic- and trans-signaling on liver damage and regeneration

Interleukin-6 (IL-6) has been suggested to play a pivotal role in liver regeneration. IL-6 on target cells activates a receptor complex consisting of the IL-6 receptor (IL-6R) and the signal transducing receptor subunit gp130. Not all cells in the body express the IL-6R on the cell surface. IL-6 can signal via two different pathways: classical signaling via the membrane bound IL-6R and IL-6 trans-signaling via a naturally occurring soluble IL-6R (sIL-6R). This second pathway widens the scope of IL-6 signaling since also cells expressing no membrane bound IL-6R can be stimulated by the trans-signal pathway. Mimicking IL-6 trans-signaling via a designer molecule, Hyper-IL-6 has been shown to accelerate liver regeneration. Another designer molecule, sgp130Fc, specifically blocks IL-6 trans-signaling. Using these proteins we investigated the contribution of IL-6 classic- and trans-signaling in the liver. Here we review the role of IL-6 signaling in response to liver damage and during liver regeneration.

Immunodrugs: therapeutic VLP-based vaccines for chronic diseases

Worldwide, the prevalence of noncommunicable chronic diseases is increasing. The use of vaccines to induce autoantibodies that neutralize disease-related proteins offers a means to effectively and affordably treat such diseases. Twenty vaccines designed to induce therapeutic autoantibodies were clinically tested in the past 12 years. Immunodrugs are therapeutic vaccines comprising virus-like particles (VLPs) covalently conjugated with self-antigens that induce neutralizing autoantibody responses. Four such VLP-based vaccines have been clinically tested and one has achieved proof of principle: a reduction of blood pressure in hypertensive patients. To facilitate preliminary clinical testing, novel nonclinical study programs have been developed. Safety study designs have considered the underlying B and T cell immunology and have examined potential toxicities of vaccine components and primary and secondary pharmacodynamic action of the vaccines.

Differential capability of human cutaneous dendritic cell subsets to initiate Th17 responses

Human skin-migratory dendritic cells (DCs) have the ability to prime and bias Th1 and Th2 CD4+ T lymphocytes. However, whether human cutaneous DCs are capable of initiating proinflammatory Th17 responses remains undetermined. We report that skin-migratory DCs stimulate allogeneic naive CD4+ T cells that differentiate simultaneously into two distinct effector Th17 and Th1 populations capable of homing to the skin, where they induce severe cutaneous damage. Skin-migratory Langerhans cells (smiLCs) were the main cutaneous DC subset capable of inducing Th17 responses dependent on the combined effects of IL-15 and stabilized IL-6, which resulted in IL-6 trans-signaling of naive CD4+ T cells. Different from smiLCs, purified skin-migratory dermal DCs did not synthesize IL-15 and were unable to bias Th17 responses. Nevertheless, these dermal DCs were capable of differentiating Th17 cells in mixed leukocyte cultures supplemented with IL-15 and stabilized IL-6. Overall, our data demonstrate that human epidermal smiLCs induce Th17 responses by mechanisms different from those previously described and highlight the need to target clinical treatments based on these variations.

Identification of cyclic peptides able to mimic the functional epitope of IgG1-Fc for human Fc gammaRI

Identification of short, structured peptides able to mimic potently protein-protein interfaces remains a challenge in drug discovery. We report here the use of a naive cyclic peptide phage display library to identify peptide ligands able to recognize and mimic IgG1-Fc functions with FcγRI. Selection by competing off binders to FcγRI with IgG1 allowed the isolation of a family of peptides sharing the common consensus sequence TX₂CXXθPXLLGCΦXE (θ represents a hydrophobic residue, Φ is usually an acidic residue, and X is any residue) and able to inhibit IgG1 binding to FcγRI. In soluble form, these peptides antagonize superoxide generation mediated by IgG1. In complexed form, they trigger phagocytosis and a superoxide burst. Unlike IgG, these peptides are strictly FcγRI-specific among the FcγRs. Molecular modeling studies suggest that these peptides can adopt 2 distinct and complementary conformers, each able to mimic the discontinuous interface contacts constituted by the Cγ2-A and -B chains of Fc for FcγRI. In addition, by covalent homodimerization, we engineered a synthetic bivalent 37-mer peptide that retains the ability to trigger effector functions. We demonstrate here that it is feasible to maintain IgG-Fc function within a small structured peptide. These peptides represent a new format for modulation of effector functions.—Bonetto, S., Spadola, L., Buchanan, A. G., Jermutus, L. Lund, J. Identification of cyclic peptides able to mimic the functional epitope of IgG1-Fc for human FcγRI.

Vaccination with IL-6 analogues induces autoantibodies to IL-6 and influences experimentally induced inflammation

IL-6 is involved in inflammation and a therapeutic target. 0.1% of Danish blood donors have nanomolar plasma concentrations of polyclonal, picomolar affinity and in vitro as well as in vivo neutralizing IgG autoantibodies to IL-6 (aAb-IL-6). Such donors are assumed to be severely IL-6 deficient; yet they appear healthy and do not exhibit overt clinical or laboratory abnormalities. We induced comparable levels of aAb-IL-6 in different mouse strains by vaccination with immunogenic IL-6 analogues. We observed that the induced aAb-IL-6 protected against collagen-induced arthritis and experimental allergic encephalitis. Furthermore, aAb-IL-6 carrying mice displayed increased plasma TNFalpha concentrations upon challenge with LPS. Taken together, induction of IL-6 autoantibodies was possible in different mouse strains. The autoantibodies influenced experimental inflammation. This immunotherapeutic principle might be a viable alternative in immune competent humans suffering from disorders driven by IL-6.