Anti-Tumor Necrosis Factor With a Glyco-Engineered Fc-Region Has Increased Efficacy in Mice With Colitis

Granzyme B PET Imaging for Assessment of Disease Activity in Inflammatory Bowel Disease

Developing a noninvasive imaging method to detect immune system activation with a high temporal resolution is key to improving inflammatory bowel disease (IBD) management. In this study, granzyme B (GZMB), typically released from cytotoxic T and natural killer cells, was targeted using PET with 68Ga-NOTA-GZP (where GZP is β-Ala-Gly-Gly-Ile-Glu-Phe-Asp-CHO) to detect early intestinal inflammation in murine models of colitis. Methods: Bioinformatic analysis was used to assess the potential of GZMB as a biomarker for detecting IBD and predicting response to treatment. Human active and quiescent Crohn disease and ulcerative colitis tissues were stained for GZMB. We used IL-10-/- mice treated with dextran sulfate sodium (DSS) as an IBD model, wild-type C57BL/6J mice as a control, and anti-tumor necrosis factor as therapy. We used a murine GZMB-binding peptide conjugated to a NOTA chelator (NOTA-GZP) labeled with 68Ga as the PET tracer. PET imaging was conducted at 1, 3, and 4 wk after colitis induction to evaluate temporal changes. Results: Bioinformatic analysis showed that GZMB gene expression is significantly upregulated in human ulcerative colitis and Crohn disease compared with the noninflamed bowel by 2.98-fold and 1.92-fold, respectively; its expression is lower by 2.16-fold in treatment responders than in nonresponders. Immunofluorescence staining of human tissues demonstrated a significantly higher GZMB in patients with active than with quiescent IBD (P = 0.032).68Ga-NOTA-GZP PET imaging showed significantly increased bowel uptake in IL-10-/- mice with DSS-induced colitis compared with vehicle-treated IL-10-/- mice (SUVmean, 0.75 vs. 0.24; P < 0.001) and both vehicle- and DSS-treated wild-type mice (SUVmean, 0.26 and 0.37; P < 0.001). In the IL-10-/- DSS-induced colitis model, the bowel PET probe uptake decreased in response to treatment with tumor necrosis factor-α (SUVmean, 0.32; P < 0.001). There was a 4-fold increase in colonic uptake of 68Ga-NOTA-GZP in the colitis model compared with the control 1 wk after colitis induction. The uptake gradually decreased to approximately 2-fold by 4 wk after IBD induction; however, the inflamed bowel uptake remained significantly higher than control at all time points (week 4 SUVmean, 0.23 vs. 0.08; P = 0.001). Conclusion: GZMB is a promising biomarker to detect active IBD and predict response to treatment. This study provides compelling evidence to translate GZMB PET for imaging IBD activity in clinical settings.

Macrophage polarization in inflammatory bowel disease

The growing prevalence of inflammatory bowel disease (IBD) has encouraged research efforts, which have contributed to gradual improvements in our understanding of IBD diagnosis and therapeutic approaches. The pathogenesis of IBD has not been fully elucidated; however, the combined actions of environmental, genetic, immune factors, and microbial organisms are believed to cause IBD. In the innate immune system, macrophages play important roles in maintaining intestinal health and in the development of IBD. Macrophages can be polarized from M0 into several phenotypes, among which M1 and M2 play critical roles in IBD development and the repair of intestinal homeostasis and damage. Certain macrophage-related IBD studies already exist; however, the functions of each phenotype have not been fully elucidated. As technology develops, understanding the link between macrophages and IBD has increased, including the growing knowledge of the developmental origins of intestinal macrophages and their performance of comprehensive functions. This review describes macrophage polarization in IBD from the perspectives of macrophage development and polarization, macrophage changes in homeostasis and IBD, metabolic changes, and the mechanisms of macrophage polarization in IBD. The discussion of these topics provides new insights into immunotherapy strategies for IBD. Video Abstract.

Signaling pathways in macrophages: molecular mechanisms and therapeutic targets

Macrophages play diverse roles in development, homeostasis, and immunity. Accordingly, the dysfunction of macrophages is involved in the occurrence and progression of various diseases, such as coronavirus disease 2019 and atherosclerosis. The protective or pathogenic effect that macrophages exert in different conditions largely depends on their functional plasticity, which is regulated via signal transduction such as Janus kinase-signal transducer and activator of transcription, Wnt and Notch pathways, stimulated by environmental cues. Over the past few decades, the molecular mechanisms of signaling pathways in macrophages have been gradually elucidated, providing more alternative therapeutic targets for diseases treatment. Here, we provide an overview of the basic physiology of macrophages and expound the regulatory pathways within them. We also address the crucial role macrophages play in the pathogenesis of diseases, including autoimmune, neurodegenerative, metabolic, infectious diseases, and cancer, with a focus on advances in macrophage-targeted strategies exploring modulation of components and regulators of signaling pathways. Last, we discuss the challenges and possible solutions of macrophage-targeted therapy in clinical applications. We hope that this comprehensive review will provide directions for further research on therapeutic strategies targeting macrophage signaling pathways, which are promising to improve the efficacy of disease treatment.

In vivo self-assembled siRNA as a modality for combination therapy of ulcerative colitis

Given the complex nature of ulcerative colitis, combination therapy targeting multiple pathogenic genes and pathways of ulcerative colitis may be required. Unfortunately, current therapeutic strategies are usually based on independent chemical compounds or monoclonal antibodies, and the full potential of combination therapy has not yet been realized for the treatment of ulcerative colitis. Here, we develop a synthetic biology strategy that integrates the naturally existing circulating system of small extracellular vesicles with artificial genetic circuits to reprogram the liver of male mice to self-assemble multiple siRNAs into secretory small extracellular vesicles and facilitate in vivo delivery siRNAs through circulating small extracellular vesicles for the combination therapy of mouse models of ulcerative colitis. Particularly, repeated injection of the multi-targeted genetic circuit designed for simultaneous inhibition of TNF-α, B7-1 and integrin α4 rapidly relieves intestinal inflammation and exerts a synergistic therapeutic effect against ulcerative colitis through suppressing the pro-inflammatory cascade in colonic macrophages, inhibiting the costimulatory signal to T cells and blocking T cell homing to sites of inflammation. More importantly, we design an AAV-driven genetic circuit to induce substantial and lasting inhibition of TNF-α, B7-1 and integrin α4 through only a single injection. Overall, this study establishes a feasible combination therapeutic strategy for ulcerative colitis, which may offer an alternative to conventional biological therapies requiring two or more independent compounds or antibodies.

Glycosylation of immunoglobin G in tumors: Function, regulation and clinical implications

Immunoglobulin G (IgG) is the predominant component in humoral immunity and the major effector of neutralizing heterogeneous antigens. Glycosylation, as excessive posttranscriptional modification, can modulate IgG immune function. Glycosylated IgG has been reported to correlate with tumor progression, presenting several characteristic modifications, including the core fucose, galactose, sialic acid, and the bisect N-acetylglucosamine (GlcNAc). Meanwhile, IgG glycosylation regulates tumor immunity involved in tumor progression and is thus a potential target. Herein, we summarized the research progression to provide novel insight into the application of IgG glycosylation in tumor diagnosis and treatment.

Mechanisms of action of anti-inflammatory proteins and peptides with anti-TNF-alpha activity and their effects on the intestinal barrier: A systematic review

Several studies in animal models of intestinal inflammation have been performed with the aim of understanding the mechanisms of action of anti-inflammatory proteins and peptides that reduce TNF-α. In order to present the best targets, effects and strategies for the treatment of intestinal inflammation in experimental models, this systematic review (SR) aimed to answer the following question: what are the mechanisms of action of molecules with anti-TNF-α activity on the intestinal barrier? The SR protocol was registered in the International Prospective Register of Systematic Reviews (PROSPERO, number CRD42019131862) and guided by the methodological procedures used for the elaboration of the SR. Articles that were part of the SR were selected considering the eligibility criteria according to the PICO (Population, Intervention, Comparison/Control and Outcomes) and were searched in the PubMed, Scopus, Web of Science, Excerpta Medica Database (EMBASE) and ScienceDirect databases. Twenty-five articles reporting studies in rats and mice were selected and the risk of bias was assessed using the tool from the SYstematic Review Center for Laboratory Animal Experimentation (SYRCLE). A descriptive synthesis of the results obtained was carried out. Based on the results, the anti-inflammatory molecules that reduced TNF-α acted mainly on the TNF-TNFR1/TNFR2 and TLR4/MD2 complex signaling pathways, and consequently on the NF-κB pathway. This improved the aspects of the inflammatory diseases studied. In addition, these mechanisms also improved the macroscopic, histological and permeability aspects in the intestine of the animals. These findings point to the potential of protein and peptide molecules that act on inflammatory pathways for medical applications with specific and promising strategic targets, aiming to improve inflammatory diseases that affect the intestine. This systematic review also highlights the need for more details during the methodological description of preclinical studies, since this was a limitation found.

The Role of Tissue-Resident Macrophages in the Development and Treatment of Inflammatory Bowel Disease

Inflammatory bowel disease (IBD), comprising Crohn’s disease and ulcerative colitis, is a refractory disease with many immune abnormalities and pathologies in the gastrointestinal tract. Because macrophages can distinguish innocuous antigens from potential pathogens to maintain mucosa barrier functions, they are essential cells in the intestinal immune system. With numerous numbers in the intestinal tract, tissue-resident macrophages have a significant effect on the constant regeneration of intestinal epithelial cells and maintaining the immune homeostasis of the intestinal mucosa. They also have a significant influence on IBD through regulating pro-(M1) or anti-inflammatory (M2) phenotype polarization according to different environmental cues. The disequilibrium of the phenotypes and functions of macrophages, disturbed by intracellular or extracellular stimuli, influences the progression of disease. Further investigation of macrophages’ role in the progression of IBD will facilitate deciphering the pathogenesis of disease and exploring novel targets to develop novel medications. In this review, we shed light on the origin and maintenance of intestinal macrophages, as well as the role of macrophages in the occurrence and development of IBD. In addition, we summarize the interaction between gut microbiota and intestinal macrophages, and the role of the macrophage-derived exosome. Furthermore, we discuss the molecular and cellular mechanisms participating in the polarization and functions of gut macrophages, the potential targeted strategies, and current clinical trials for IBD.

How Do We Predict a Patient's Disease Course and Whether They Will Respond to Specific Treatments?

Gastroenterologists will be all too familiar with the difficult decisions that managing inflammatory bowel disease often presents. How aggressively should I treat this patient? Do I expect them to have a mild or aggressive form of disease? Do they need a biologic? If so, which one? And when should I start it? The reality is that the answers that would be right for one patient might be disastrous for another. The growing therapeutic armamentarium will only make these decisions more difficult, and yet, we have seen how other specialties have begun to use the molecular heterogeneity in their diseases to provide some answers. Here, we review the progress that has been made in predicting the future for any given patient with inflammatory bowel disease-whether that is the course of disease that they will experience or whether or not they will respond to, or indeed tolerate, a particular therapy.

Long-term exposure to monoclonal anti-TNF is associated with an increased risk of lymphoma in BAFF-transgenic mice

The impact of treatment on the risk of lymphoma in patients with rheumatoid arthritis (RA) is unclear. Here, we aimed to assess if the risk of lymphoma differs according to the type of tumor necrosis factor inhibitor (TNFi), comparing monoclonal anti-TNF antibodies to the soluble TNF receptor. We used B cell activating factor belonging to the TNF family (BAFF)-transgenic (Tg) mice as a model of autoimmunity-associated lymphoma. Six-month-old BAFF-Tg mice were treated with TNFi for 12 months. Histological examination of the spleen, assessment of the cellular composition of the spleen by flow cytometry and assessment of B cell clonality were performed at euthanasia. Crude mortality and incidence of lymphoma were significantly higher in mice treated with monoclonal anti-TNF antibodies compared to both controls and mice treated with the soluble TNF receptor, even at a high dose. Flow cytometry analysis revealed decreased splenic macrophage infiltration in mice treated with monoclonal anti-TNF antibodies. Overall, this study demonstrates, for the first time, that a very prolonged treatment with monoclonal anti-TNF antibodies increase the risk of lymphoma in B cell-driven autoimmunity. These data suggest a closer monitoring for lymphoma development in patients suffering from B cell-driven autoimmune disease with long-term exposure to monoclonal anti-TNF antibodies.

Transmembrane TNF and Its Receptors TNFR1 and TNFR2 in Mycobacterial Infections

Tumor necrosis factor (TNF) is one of the main cytokines regulating a pro-inflammatory environment. It has been related to several cell functions, for instance, phagocytosis, apoptosis, proliferation, mitochondrial dynamic. Moreover, during mycobacterial infections, TNF plays an essential role to maintain granuloma formation. Several effector mechanisms have been implicated according to the interactions of the two active forms, soluble TNF (solTNF) and transmembrane TNF (tmTNF), with their receptors TNFR1 and TNFR2. We review the impact of these interactions in the context of mycobacterial infections. TNF is tightly regulated by binding to receptors, however, during mycobacterial infections, upstream activation signalling pathways may be influenced by key regulatory factors either at the membrane or cytosol level. Detailing the structure and activation pathways used by TNF and its receptors, such as its interaction with solTNF/TNFRs versus tmTNF/TNFRs, may bring a better understanding of the molecular mechanisms involved in activation pathways which can be helpful for the development of new therapies aimed at being more efficient against mycobacterial infections.

Macrophage polarization: an effective approach to targeted therapy of inflammatory bowel disease

Introduction: Inflammatory bowel disease (IBD) is a systemic disease with immune abnormalities that can affect the entire digestive tract. A high percentage of patients with IBD are unresponsive to current pharmacological agents, hence the need exists for novel therapeutic approaches. There is compelling evidence that macrophage polarization plays a key role in the remission of IBD patients and that it could open up future treatment options for patients.Areas covered: This paper highlights the crucial role of macrophage polarization in IBD. The authors shed light on the phenotype and function of macrophages and potential drug targets for polarization regulation. Existing approaches for regulating macrophage polarization are discussed and potential solutions for safety concerns are considered. We performed a literature search on the IBD and macrophage polarization mainly published in PubMed January 2010-July 2020.Expert opinion: Evidence indicates that there are fewer M2 macrophages and a high proportion of M1 macrophages in the intestinal tissues of individuals who are non- responsive to treatment. Regulating macrophage polarization is a potential novel targeted option for IBD treatment. Improved mechanistic insights are required to uncover more precise and effective targets for skewing macrophages into a proper phenotype.

Monocyte TREM-1 Levels Associate With Anti-TNF Responsiveness in IBD Through Autophagy and Fcγ-Receptor Signaling Pathways

The expression of Triggering Receptor Expressed on Myeloid cells (TREM)-1 has been described as a predictive marker for anti-Tumor Necrosis Factor (TNF)-α monoclonal antibody (mAb) therapy responsiveness in patients with inflammatory bowel disease (IBD). Here we investigated expression of TREM-1 specifically in CD14+ monocytes in relation to anti-TNF response. The pretreatment TREM-1 expression levels of CD14+ monocytes of Crohn's disease (CD) patients were predictive of outcome to anti-TNF mAb therapy, with low TREM-1 expression associated with response to anti-TNF. FACSorting of CD14+ monocytes with different TREM-1 levels showed that differentiation towards regulatory CD206+ M2 type macrophages by anti-TNF was suppressed in CD14+ monocytes with high TREM-1 expression. Activity of the Fcγ-Receptor and autophagy pathway, both necessary for M2 type differentiation and the response to anti-TNF, were decreased in CD14+ monocytes with high expression of TREM-1. We confirmed that the activity of the Fcγ-Receptor pathway was decreased in the CD patients that did not respond to anti-TNF therapy and that it was negatively correlated with TREM-1 expression levels in the CD patient cohort. In conclusion, our results indicate that TREM-1 expression levels in CD14+ monocytes associate with decreased autophagy and FcγR activity resulting in decreased differentiation to M2 type regulatory macrophages upon anti-TNF mAb treatment, which may explain anti-TNF non-response in IBD patients with high expression levels of TREM-1.

Fucosylation in the intestinal mucosa and inflammatory bowel disease

Inflammatory bowel disease (IBD) is an unexplained, abnormal immune mediated chronic and recurrent inflammatory disorder of the intestine. Fucosylation in the intestinal mucosal is the process of transferring fucose to intestinal mucosal protein side chains under the control of fucosyltransferases to form fucosyl bonds. The mechanism of fucosylation in the intestinal mucosa in IBD has not been fully proved. In this paper, we will review the progress in understanding the relationship between fucosylation in the intestinal mucosa and IBD.

Evolution of infliximab biosimilar in inflammatory bowel disease: from intravenous to subcutaneous CT-P13

INTRODUCTION

Biologic drugs have significantly improved the treatment of ulcerative colitis (UC) and Crohn's disease (CD). However, the availability of these drugs is limited by their high cost. Infliximab was the first biologic to be approved for inflammatory bowel diseases (IBD). After its patent expired other manufactures developed biosimilar versions, among which CT-P13, and licensed them thorough an expedite process.

AREAS COVERED

The aim of this review is to summarize the available evidence on CT-P13 use in IBD, with particular interest in the phase II trials of a subcutaneous version of CT-P13.

EXPERT OPINION

Biosimilars, such as CT-P13, are an important resource for health-care systems. Although CT-P13 approval in IBD was based on extrapolation, subsequent studies confirmed its clinical equivalence to originator infliximab. A new subcutaneous formulation of CT-P13 showed promising results in phase I and II trials in both CD and UC. Clinical efficacy and safety were comparable and interestingly serum drug doses appeared to be more stable than conventional intravenous CT-P13. If these preliminary results will be confirmed, the first sub-cutaneous version of infliximab could soon be available for IBD.

Biological therapy in pediatric age

Biological therapies, especially blocking tumor necrosis factor-α (TNFα) agents have radically changed the therapeutic approach and disease course of pediatric inflammatory bowel disease (IBD). In particular, drugs such as infliximab (IFX) and adalimumab (ADA) have been demonstrated to be effective in inducing and maintaining corticosteroid-free remission in both adult and pediatric patients with Crohns Disease (CD) and Ulcerative colitis (UC). Biosimilar biological (BioS) therapy is increasingly being used in pediatric age even though most knowledge on the safety and efficacy of these agents is based on IFX in adult IBD data. Studies show high rates of clinical response and remission in both IFX naïve patients and in patients switched from originator to BioS with similar risks of adverse events (AEs) as those reported with IFX originator. In the present review indications, efficacy and AEs of biological therapy in pediatric IBD will be discussed, as well as the role of other biological agents such as Golimumab, Vedolizumab and Ustekinumab, the role of BioS biological therapy and utility of therapeutic drug monitoring in clinical practice.

Anti-TNF therapy in IBD exerts its therapeutic effect through macrophage IL-10 signalling

OBJECTIVE

Macrophage interleukin (IL)-10 signalling plays a critical role in the maintenance of a regulatory phenotype that prevents the development of IBD. We have previously found that anti-tumour necrosis factor (TNF) monoclonal antibodies act through Fcγ-receptor (FcγR) signalling to promote repolarisation of proinflammatory intestinal macrophages to a CD206+ regulatory phenotype. The role of IL-10 in anti-TNF-induced macrophage repolarisation has not been examined.

DESIGN

We used human peripheral blood monocytes and mouse bone marrow-derived macrophages to study IL-10 production and CD206+ regulatory macrophage differentiation. To determine whether the efficacy of anti-TNF was dependent on IL-10 signalling in vivo and in which cell type, we used the CD4+CD45Rb^high T-cell transfer model in combination with several genetic mouse models.

RESULTS

Anti-TNF therapy increased macrophage IL-10 production in an FcγR-dependent manner, which caused differentiation of macrophages to a more regulatory CD206+ phenotype in vitro. Pharmacological blockade of IL-10 signalling prevented the induction of these CD206+ regulatory macrophages and diminished the therapeutic efficacy of anti-TNF therapy in the CD4+CD45Rb^high T-cell transfer model of IBD. Using cell type-specific IL-10 receptor mutant mice, we found that IL-10 signalling in macrophages but not T cells was critical for the induction of CD206+ regulatory macrophages and therapeutic response to anti-TNF.

CONCLUSION

The therapeutic efficacy of anti-TNF in resolving intestinal inflammation is critically dependent on IL-10 signalling in macrophages.

The Ligands for Human IgG and Their Effector Functions

Activation of the humoral immune system is initiated when antibodies recognize an antigen and trigger effector functions through the interaction with Fc engaging molecules. The most abundant immunoglobulin isotype in serum is Immunoglobulin G (IgG), which is involved in many humoral immune responses, strongly interacting with effector molecules. The IgG subclass, allotype, and glycosylation pattern, among other factors, determine the interaction strength of the IgG-Fc domain with these Fc engaging molecules, and thereby the potential strength of their effector potential. The molecules responsible for the effector phase include the classical IgG-Fc receptors (FcγR), the neonatal Fc-receptor (FcRn), the Tripartite motif-containing protein 21 (TRIM21), the first component of the classical complement cascade (C1), and possibly, the Fc-receptor-like receptors (FcRL4/5). Here we provide an overview of the interactions of IgG with effector molecules and discuss how natural variation on the antibody and effector molecule side shapes the biological activities of antibodies. The increasing knowledge on the Fc-mediated effector functions of antibodies drives the development of better therapeutic antibodies for cancer immunotherapy or treatment of autoimmune diseases.

A JAK1 Selective Kinase Inhibitor and Tofacitinib Affect Macrophage Activation and Function

BACKGROUND

Janus kinases (JAKs) mediate cytokine signaling involved in inflammatory bowel disease. The pan-JAK inhibitor tofacitinib has shown efficacy in the treatment of ulcerative colitis. However, concerns regarding adverse events due to their wide spectrum inhibition fueled efforts to develop selective JAK inhibitors. Given the crucial role of myeloid cells in intestinal immune homeostasis, we evaluated the effect of pan-JAK and selective JAK inhibitors on pro- and anti-inflammatory macrophage polarization and function (M1/M2) and in experimental colitis.

METHODS

Murine bone marrow-derived macrophages or human monocytes were treated using JAK1 and JAK3 selective inhibitors (JAK1i;JAK3i) and tofacitinib and were evaluated by transcriptional, functional, and metabolic analyses. In vivo, oral administration of JAK1i and tofacitinib (10 or 30 mg/kg) was tested in both acute and acute rescue dextran sodium sulfate (DSS) colitis.

RESULTS

Both tofacitinib and JAK1i but not JAK3i effectively inhibited STAT1 phosphorylation and interferon gamma-induced transcripts in M1 polarized macrophages. Strikingly, transcriptional profiling suggested a switch from M1 to M2 type macrophages, which was supported by increased protein expression of M2-associated markers. In addition, both inhibitors enhanced oxidative phosphorylation rates. In vivo, JAK1i and tofacitinib did not protect mice from acute DSS-induced colitis but ameliorated recovery from weight loss and disease activity during acute rescue DSS-induced colitis at the highest dose.

CONCLUSION

JAK1i and tofacitinib but not JAK3i induce phenotypical and functional characteristics of anti-inflammatory macrophages, suggesting JAK1 as the main effector pathway for tofacitinib in these cells. In vivo, JAK1i and tofacitinib modestly affect acute rescue DSS-induced colitis.

TNF-anti-TNF Immune Complexes Inhibit IL-12/IL-23 Secretion by Inflammatory Macrophages via an Fc-dependent Mechanism

BACKGROUND AND AIMS

We have recently shown that the mode of action of IgG1 anti-tumour necrosis factor [TNF] antibodies in inflammatory bowel disease [IBD] requires Fcγ-receptor [FcγR] engagement on macrophages. Here we examine the effect of Fcγ-receptor signalling by anti-TNF on macrophage IL-12/IL-23 secretion.

METHODS

Cytokine production by human inflammatory macrophages was assessed at the level of RNA and protein. TNF-anti-TNF immune complex formation was determined by size-exclusion chromatography and signalling visualized by immunofluorescence. IL-12/IL-23p40 was measured in CD14+ lamina propria cells from IBD patients.

RESULTS

Infliximab and adalimumab potently suppressed IL-12/IL-23 production by inflammatory macrophages, but Fab' fragment certolizumab did not. IL-12/IL-23 suppression depended on Syk activity and was mediated at the level of IL-12/IL-23p40 mRNA. Etanercept, a soluble TNF receptor fused to an Fc-region, did not inhibit IL-12/L-23 secretion, suggesting that the presence of an Fc-region was not sufficient. Infliximab and adalimumab formed immune complexes with soluble TNF whereas etanercept did not, suggesting that FcγR-mediated suppression of IL-12/IL-23 required the formation of immune complexes. Indeed, non-specific IgG1 immune complexes, but not uncomplexed IgG1, similarly suppressed IL-12/IL-23 secretion. Finally, infliximab significantly decreased IL-12/IL-23p40 production in myeloid cells isolated from the lamina propria of IBD patients.

CONCLUSIONS

TNF-anti-TNF antibody immune complexes potently inhibit IL-12/IL-23 expression by inflammatory macrophages. Our data suggest that anti-TNFs and antibodies against IL-12/IL-23 may therefore have partially overlapping modes of action in patients with IBD.

A New Venue of TNF Targeting

The first Food and Drug Administration-(FDA)-approved drugs were small, chemically-manufactured and highly active molecules with possible off-target effects, followed by protein-based medicines such as antibodies. Conventional antibodies bind a specific protein and are becoming increasingly important in the therapeutic landscape. A very prominent class of biologicals are the anti-tumor necrosis factor (TNF) drugs that are applied in several inflammatory diseases that are characterized by dysregulated TNF levels. Marketing of TNF inhibitors revolutionized the treatment of diseases such as Crohn’s disease. However, these inhibitors also have undesired effects, some of them directly associated with the inherent nature of this drug class, whereas others are linked with their mechanism of action, being pan-TNF inhibition. The effects of TNF can diverge at the level of TNF format or receptor, and we discuss the consequences of this in sepsis, autoimmunity and neurodegeneration. Recently, researchers tried to design drugs with reduced side effects. These include molecules with more specificity targeting one specific TNF format or receptor, or that neutralize TNF in specific cells. Alternatively, TNF-directed biologicals without the typical antibody structure are manufactured. Here, we review the complications related to the use of conventional TNF inhibitors, together with the anti-TNF alternatives and the benefits of selective approaches in different diseases.

Combination Immunosuppression in IBD

Whether to use biologic treatment for inflammatory bowel disease as monotherapy or in combination with immunosuppressives has been a matter of debate in the last 2 decades. Combination therapy was not superior in any of the registration trials for Crohn's disease and ulcerative colitis for TNF antagonists, vedolizumab, or ustekinumab. It needs to be mentioned, though, that none of these trials were powered to detect such differences, and that many patients entered the trial after having failed conventional immunosuppressives.Postmarketing studies revealed that patients on background immunosuppression have a lower risk of immunogenicity (often resulting in infusion/injection reactions) than patients on monotherapy. In the SONIC and UC-SUCCESS trials, superiority of the combination azathioprine-infliximab was demonstrated in Crohn's disease and ulcerative colitis, respectively. This trial design has not been used with any other biologic for IBD, so far. Meanwhile, it has also become clear that combination treatment with TNF antagonists is associated with increased toxicity, mainly infections, but also malignancy such as lymphoproliferative disease. This toxicity could perhaps be reduced by using lower doses of immunosuppressives, a strategy that has been shown to be equally potent in reducing immunogenicity. Additionally, combination treatment could be used for a limited period of time (12 months or even shorter) since most immunogenicity develops in the beginning of the biologic treatment. Patients who develop anti-drug-antibodies later on can often be rescued by reintroduction of thiopurines or methotrexate.In summary, combination treatment is certainly beneficial with infliximab, at least in the first 12 months of treatment. With other TNF antagonists, vedolizumab, and ustekinumab, the available data do not offer clear guidance. In patients without increased risk of toxicity, and certainly in those with limited treatment options, it may be wise to offer combination treatment with all biologics for the time being and at least during the initiation phase.