Cytokines in chronic inflammatory arthritis. II. Granulocyte-macrophage colony-stimulating factor in rheumatoid synovial effusions

Nathan Zvaifler

Nathan Zvaifler was one of the most original thinkers in the field of rheumatology contributing to modern understanding of the role of complement in mediating inflammation and the role of synoviocytes in the pathogenesis of the destructive changes of rheumatoid arthritis. His clinical acumen was unparalleled and his students are still in awe of the breadth of his knowledge.

Anti-GM-CSF otilimab versus tofacitinib or placebo in patients with active rheumatoid arthritis and an inadequate response to conventional or biologic DMARDs: two phase 3 randomised trials (contRAst 1 and contRAst 2)

OBJECTIVES

To investigate the efficacy and safety of otilimab, an antigranulocyte-macrophage colony-stimulating factor antibody, in patients with active rheumatoid arthritis.

METHODS

Two phase 3, double-blind randomised controlled trials including patients with inadequate responses to methotrexate (contRAst 1) or conventional synthetic/biologic disease-modifying antirheumatic drugs (cs/bDMARDs; contRAst 2). Patients received background csDMARDs. Through a testing hierarchy, subcutaneous otilimab (90/150 mg once weekly) was compared with placebo for week 12 endpoints (after which, patients receiving placebo switched to active interventions) or oral tofacitinib (5 mg two times per day) for week 24 endpoints.

PRIMARY ENDPOINT

proportion of patients achieving an American College of Rheumatology response ≥20% (ACR20) at week 12.

RESULTS

The intention-to-treat populations comprised 1537 (contRAst 1) and 1625 (contRAst 2) patients.

PRIMARY ENDPOINT

proportions of ACR20 responders were statistically significantly greater with otilimab 90 mg and 150 mg vs placebo in contRAst 1 (54.7% (p=0.0023) and 50.9% (p=0.0362) vs 41.7%) and contRAst 2 (54.9% (p<0.0001) and 54.5% (p<0.0001) vs 32.5%). Secondary endpoints: in both trials, compared with placebo, otilimab increased the proportion of Clinical Disease Activity Index (CDAI) low disease activity (LDA) responders (not significant for otilimab 150 mg in contRAst 1), and reduced Health Assessment Questionnaire-Disability Index (HAQ-DI) scores. Benefits with tofacitinib were consistently greater than with otilimab across multiple endpoints. Safety outcomes were similar across treatment groups.

CONCLUSIONS

Although otilimab demonstrated superiority to placebo in ACR20, CDAI LDA and HAQ-DI, improved symptoms, and had an acceptable safety profile, it was inferior to tofacitinib.

TRIAL REGISTRATION NUMBERS

NCT03980483, NCT03970837.

Emerging aspects of cytokine storm in COVID-19: The role of proinflammatory cytokines and therapeutic prospects

COVID-19 has claimed millions of lives during the last 3 years since initial cases were reported in Wuhan, China, in 2019. Patients with COVID-19 suffer from severe pneumonia, high fever, acute respiratory distress syndrome (ARDS), and multiple-organ dysfunction, which may also result in fatality in extreme cases. Cytokine storm (CS) is hyperactivation of the immune system, wherein the dysregulated production of proinflammatory cytokines could result in excessive immune cell infiltrations in the pulmonary tissues, resulting in tissue damage. The immune cell infiltration could also occur in other tissues and organs and result in multiple organs' dysfunction. The key cytokines implicated in the onset of disease severity include TNF-α, IFN-γ, IL-6, IL-1β, GM-CSF, and G-CSF. Controlling the CS is critical in treating COVID-19 disease. Therefore, different strategies are employed to mitigate the effects of CS. These include using monoclonal antibodies directed against soluble cytokines or the cytokine receptors, combination therapies, mesenchymal stem cell therapy, therapeutic plasma exchange, and some non-conventional treatment methods to improve patient immunity. The current review describes the role/s of critical cytokines in COVID-19-mediated CS and the respective treatment modalities.

Translating the biology of β common receptor-engaging cytokines into clinical medicine

The family of cytokines that comprises IL-3, IL-5, and GM-CSF was discovered over 30 years ago, and their biological activities and resulting impact in clinical medicine has continued to expand ever since. Originally identified as bone marrow growth factors capable of acting on hemopoietic progenitor cells to induce their proliferation and differentiation into mature blood cells, these cytokines are also recognized as key mediators of inflammation and the pathobiology of diverse immunologic diseases. This increased understanding of the functional repertoire of IL-3, IL-5, and GM-CSF has led to an explosion of interest in modulating their functions for clinical management. Key to the successful clinical translation of this knowledge is the recognition that these cytokines act by engaging distinct dimeric receptors and that they share a common signaling subunit called β-common or βc. The structural determination of how IL-3, IL-5, and GM-CSF interact with their receptors and linking this to their differential biological functions on effector cells has unveiled new paradigms of cell signaling. This knowledge has paved the way for novel mAbs and other molecules as selective or pan inhibitors for use in different clinical settings.

The monocyte-to-osteoclast transition in rheumatoid arthritis: Recent findings

Rheumatoid arthritis (RA) is an autoimmune disease characterized by joint inflammation leading to joint destruction and deformity. The crucial role of osteoclasts in the bone erosion in RA has been demonstrated. Deregulated osteoclastogenesis which is affected by environmental factors including the inflammatory state, as well as genetic and epigenetic factors, is one of hallmarks of RA pathogenesis. An enhanced-monocyte-to-osteoclast transition plays an important role in osteoclast upregulation in RA because under specific stimuli, circulating monocytes might migrate to a specific location in the bones and fuse with each other to become mature multinucleated osteoclasts. To understand the mechanism of bone damage in RA and to develop novel treatments targeting osteoclast upregulation, it is important to clarify our understanding of the monocyte-to-osteoclast transition in RA. Several potential targets which inhibit both inflammation and osteoclastogenesis, as well as regulators that affect the monocyte-to-osteoclast transition have been revealed by recent studies. Here, we review the factors affecting osteoclastogenesis in RA, summarize the anti-osteoclastogenic effects of current RA treatments, and identify promising therapeutic targets relating to both inflammation and osteoclastogenesis.

Pathway Phenotypes Underpinning Depression, Anxiety, and Chronic Fatigue Symptoms Due to Acute Rheumatoid Arthritis: A Precision Nomothetic Psychiatry Analysis

Rheumatoid arthritis (RA) is a chronic inflammatory and autoimmune disorder which affects the joints in the wrists, fingers, and knees. RA is often associated with depressive and anxiety symptoms as well as chronic fatigue syndrome (CFS)-like symptoms. This paper examines the association between depressive symptoms (measured with the Beck Depression Inventory, BDI), anxiety (Hamilton Anxiety Rating Scale, HAMA), CFS-like (Fibro-fatigue Scale) symptoms and immune–inflammatory, autoimmune, and endogenous opioid system (EOS) markers, and lactosylcer-amide (CD17) in RA. The serum biomarkers were assayed in 118 RA and 50 healthy controls. Results were analyzed using the new precision nomothetic psychiatry approach. We found significant correlations between the BDI, FF, and HAMA scores and severity of RA, as assessed with the DAS28-4, clinical and disease activity indices, the number of tender and swollen joints, and patient and evaluator global assessment scores. Partial least squares analysis showed that 69.7% of the variance in this common core underpinning psychopathology and RA symptoms was explained by immune–inflammatory pathways, rheumatoid factor, anti-citrullinated protein antibodies, CD17, and mu-opioid receptor levels. We constructed a new endophenotype class comprising patients with very high immune–inflammatory markers, CD17, RA, affective and CF-like symptoms, and tobacco use disorder. We extracted a reliable and replicable latent vector (pathway phenotype) from immune data, psychopathology, and RA-severity scales. Depression, anxiety, and CFS-like symptoms due to RA are manifestations of the phenome of RA and are mediated by the effects of the same immune–inflammatory, autoimmune, and other pathways that underpin the pathophysiology of RA.

Targeting GM-CSF in inflammatory and autoimmune disorders

Granulocyte macrophage-colony stimulating factor (GM-CSF) was originally identified as a growth factor for its ability to promote the proliferation and differentiation in vitro of bone marrow progenitor cells into granulocytes and macrophages. Many preclinical studies, using GM-CSF deletion or depletion approaches, have demonstrated that GM-CSF has a wide range of biological functions, including the mediation of inflammation and pain, indicating that it can be a potential target in many inflammatory and autoimmune conditions. This review provides a brief overview of GM-CSF biology and signaling, and summarizes the findings from preclinical models of a range of inflammatory and autoimmune disorders and the latest clinical trials targeting GM-CSF or its receptor in these disorders.

JTE-952 Suppresses Bone Destruction in Collagen-Induced Arthritis in Mice by Inhibiting Colony Stimulating Factor 1 Receptor

Rheumatoid arthritis (RA) is a chronic autoimmune disease characterized by synovial inflammation and structural destruction of the joints. Bone damage occurs in an early stage after onset and osteoclast activation plays a substantial role in its progression. Colony stimulating factor 1 receptor (CSF1R) is a receptor protein tyrosine kinase specifically expressed in monocytic-lineage cells such as macrophages and osteoclasts. Here, we investigated the effect of JTE-952, a novel CSF1R tyrosine kinase inhibitor, on osteoclast formation in vitro and on bone destruction in a mouse model of collagen-induced arthritis. JTE-952 completely inhibited osteoclast differentiation from human monocytes, with an IC₅₀ of 2.8 nmol/L, and reduced osteoclast formation from the synovial cells of RA patients. Detectable levels of colony stimulating factor 1 (CSF1), a ligand of CSF1R, were observed in the synovial tissues of the arthritis model, similar to those observed in the pathology of human RA. JTE-952 significantly suppressed increases in the bone destruction score, the number of tartrate-resistant-acid-phosphatase-positive cells, and the severity of arthritis in the model mice. We also examined the efficacy of JTE-952 combined with methotrexate. This combination therapy more effectively reduced the severity of bone destruction and arthritis than monotherapy with either agent alone. In summary, JTE-952 potently inhibited human osteoclast formation in vitro and suppressed bone destruction in an experimental arthritis model, especially when combined with methotrexate. These results indicate that JTE-952 should strongly inhibit bone destruction and joint inflammation in RA patients and effectively prevent the progression of the structural destruction of joints.

Amelioration of Graft-versus-Host Disease by Exopolysaccharide from a Commensal Bacterium

Acute graft-versus-host disease (aGvHD) is a severe, often lethal, complication of hematopoietic stem cell transplantation, and although prophylactic regimens are given as standard pretransplantation therapy, up to 60% of these patients develop aGvHD, and require additional immunosuppressive intervention. We treated mice with a purified probiotic molecule, exopolysaccharide (EPS) from Bacillus subtilis, shortly before and after induction of aGvHD and found that, whereas only 10% of control mice survived to day 80, 70% of EPS-treated mice survived to 80 d. EPS treatment of donor-only mice resulted in ∼60% survival. Using a biosensor mouse model to assess inflammation in live mice during aGvHD, we found that EPS prevented the activation of alloreactive donor T cells. In vitro, EPS did not affect T cells directly but, instead, induced bone marrow-derived dendritic cells (BMDCs) that displayed characteristics of inhibitory dendritic cells (DCs). Development of these BMDCs required TLR4 signaling through both MyD88 and TRIF pathways. Using BMDCs derived from IDO knockout mice, we showed that T cell inhibition by EPS-treated BMDCs was mediated through the suppressive effects of IDO. These studies describe a bacterial molecule that modulates immune responses by inducing inhibitory DCs in a TLR4-dependent manner, and these cells have the capacity to inhibit T cell activation through IDO. We suggest that EPS or EPS-treated DCs can serve as novel agents for preventing aGvHD.

The Jak/STAT pathway: A focus on pain in rheumatoid arthritis

Pain is a manifestation of rheumatoid arthritis (RA) that is mediated by inflammatory and non-inflammatory mechanisms and negatively affects quality of life. Recent findings from a Phase 3 clinical trial showed that patients with RA who were treated with a Janus kinase 1 (Jak1) and Janus kinase 2 (Jak2) inhibitor achieved significantly greater improvements in pain than those treated with a tumor necrosis factor blocker; both treatments resulted in similar changes in standard clinical measures and markers of inflammation. These findings suggest that Jak1 and Jak2 inhibition may relieve pain in RA caused by inflammatory and non-inflammatory mechanisms and are consistent with the overarching involvement of the Jak-signal transducer and activator of transcription (Jak/STAT) pathway in mediating the action, expression, and regulation of a multitude of pro- and anti-inflammatory cytokines. In this review, we provide an overview of pain in RA, the underlying importance of cytokines regulated directly or indirectly by the Jak/STAT pathway, and therapeutic targeting of the Jak/STAT pathway in RA. As highlighted herein, multiple cytokines directly or indirectly regulated by the Jak/STAT pathway play important roles in mediating various mechanisms underlying pain in RA. Having a better understanding of these mechanisms may help clinicians make treatment decisions that optimize the control of inflammation and pain.

Efficacy, patient-reported outcomes, and safety of the anti-granulocyte macrophage colony-stimulating factor antibody otilimab (GSK3196165) in patients with rheumatoid arthritis: a randomised, phase 2b, dose-ranging study

BACKGROUND

The human monoclonal antibody otilimab inhibits granulocyte-macrophage colony-stimulating factor (GM-CSF), a key driver in immune-mediated inflammatory conditions. We aimed to evaluate the efficacy, safety, and key patient-reported outcomes related to pain in patients with active rheumatoid arthritis receiving otilimab.

METHODS

This phase 2b, dose-ranging, multicentre, placebo-controlled study was done at 64 sites across 14 countries. Patients aged 18 years or older with rheumatoid arthritis who were receiving stable methotrexate were randomly assigned (1:1:1:1:1:1) to subcutaneous placebo or otilimab 22·5 mg, 45 mg, 90 mg, 135 mg, or 180 mg, plus methotrexate, once weekly for 5 weeks, then every other week until week 50. The randomisation schedule was generated by the sponsor, and patients were assigned to treatment by interactive response technology. Randomisation was blocked (block size of six) but was not stratified. Investigators, patients, and the sponsor were blinded to treatment. An unblinded administrator prepared and administered the study drug. The primary endpoint was the proportion of patients who achieved disease activity score for 28 joints with C-reactive protein (DAS28-CRP) <2·6 at week 24. Patients who were not in the otilimab 180 mg group, without a good or moderate European League Against Rheumatism response (week 12) or with DAS28-CRP >3·2 (week 24) escaped to otilimab 180 mg. Patients who escaped were treated as non-responders in their original assigned group. Safety endpoints were incidence of adverse events and serious adverse events, infections, and pulmonary events. Efficacy and safety outcomes were assessed in the intention-to-treat population. This study is registered with ClinicalTrials.gov, NCT02504671.

FINDINGS

Between July 23, 2015, and Dec 29, 2017, 222 patients were randomly assigned (37 to each group). 86 (49%) of 175 escaped to otilimab 180 mg at week 12 and 57 (69%) of 83 at week 24. At week 24, the proportion of patients with DAS28-CRP <2·6 was two (5%) of 37 in the otilimab 22·5 mg group, six (16%) of 37 in the 45 mg group, seven (19%) of 37 in the 90 mg group, five (14%) of 37 in the 135 mg group, five (14%) of 37 in the 180 mg, and one (3%) of 37 in the placebo group. The largest difference was achieved with otilimab 90 mg (16·2%; odds ratio [OR] 8·39, 95% CI 0·98-72·14; p=0·053). Adverse events were reported pre-escape in 19-24 (51-65%) patients and post escape in 10-17 (40-61%) patients across otilimab dose groups and in 18 (49%) of 37 and 22 (67%) of 33 in the placebo group. The most common adverse event was nasopharyngitis: 3-9 (8-24%) in otilimab groups and one (3%) in the placebo group pre-escape and 1-3 (4-10%) in otilimab groups and seven (21%) in the placebo group post escape. Pre-escape serious adverse events were foot fracture (otilimab 45 mg); arthralgia, myocardial infarction, dizziness (otilimab 90 mg); oesophageal spasm, acute pyelonephritis (otilimab 22·5 mg), and uterine leiomyoma (otilimab 135 mg). Post-escape serious adverse events were ankle fracture (placebo) and rheumatoid arthritis (otilimab 135 mg). There were no deaths or pulmonary events of clinical concern, and rates of serious infection were low.

INTERPRETATION

Otilimab plus methotrexate was well tolerated and, despite not achieving the primary endpoint of DAS28-CRP remission, there were improvements compared with placebo in disease activity scores. Of note, patients reported significant improvement in pain and physical function, supporting further clinical development of otilimab in rheumatoid arthritis.

FUNDING

GlaxoSmithKline.

MRI of the joint and evaluation of the granulocyte-macrophage colony-stimulating factor-CCL17 axis in patients with rheumatoid arthritis receiving otilimab: a phase 2a randomised mechanistic study

BACKGROUND

Otilimab is a human monoclonal antibody that inhibits granulocyte-macrophage colony-stimulating factor (GM-CSF), a driver in many immune-mediated inflammatory conditions. We evaluated the effect of otilimab on the GM-CSF-chemokine (C-C motif) ligand 17 (CCL17) axis and synovitis in patients with rheumatoid arthritis.

METHODS

This phase 2a, randomised, double-blind, multicentre, placebo-controlled, parallel-group study was done at nine sites across the USA, Poland, and Germany. Patients aged 18 years or older with rheumatoid arthritis per American College of Rheumatology-European League Against Rheumatism 2010 criteria and receiving stable methotrexate were randomly assigned (3:1) by an interactive response technology system to either subcutaneous otilimab 180 mg or placebo once weekly for 5 weeks, then every other week until week 10 (within a 12-week treatment period), followed by a 10-week safety follow-up. Randomisation was stratified by early rheumatoid arthritis (≤2 years since diagnosis) and established rheumatoid arthritis (>2 years since diagnosis). Patients and study personnel (except for an unblinded coordinator or nurse who prepared and administered the study drug) were blinded to treatment assignment; the syringe was shielded during administration. Patients were enrolled by study investigators and allocated to a treatment by central randomisation on the basis of a schedule generated by the sponsor. The primary endpoint was change over time (assessed at baseline and weeks 1, 2, 4, 6, 8, 12, and 22 of follow-up) in 112 biomarkers, including target engagement biomarkers and those that may be indicative of rheumatoid arthritis disease activity and response to otilimab. Secondary endpoints were change from baseline in synovitis, osteitis and erosion assessed by rheumatoid arthritis MRI scoring system (RAMRIS) and rheumatoid arthritis MRI quantitative score (RAMRIQ), and safety evaluation. The primary, secondary, and safety endpoints were assessed in the intention-to-treat population. Biomarker and MRI endpoints were analysed for differences between treatment groups using a repeated measures model. This study is registered with ClinicalTrials.gov, NCT02799472.

FINDINGS

Between Aug 9, 2016, and Oct 30, 2017, 39 patients were randomly assigned and included in the analysis (otilimab n=28; placebo n=11). In the otilimab group, mean serum concentrations of GM-CSF-otilimab complex peaked at week 4 (138·4 ng/L, 95% CI 90·0-212·9) but decreased from week 6-12. CCL17 concentrations decreased from baseline to week 1, remained stable to week 8, and returned to baseline at week 12; least-squares mean ratio to baseline was 0·65 (95% CI 0·49-0·86; coefficient of variation 13·60) at week 2, 0·68 (0·53-0·88; 12·51) at week 4, 0·78 (0·60-1·00; 12·48) at week 6, and 0·68 (0·54-0·85; 11·21) at week 8. No meaningful change in CCL17 concentrations was observed with placebo. In the otilimab group, the least-squares mean ratio to baseline in MMP-degraded type I collagen was 0·86-0·91 over weeks 1-8, returning to baseline at week 12; concentrations remained above baseline at all timepoints in the placebo group. There were no observable differences between otilimab and placebo for all other biomarkers. At week 12, least-squares mean change in RAMRIS synovitis score from baseline was -1·3 (standard error [SE] 0·6) in the otilimab group and 0·8 (1·2) with placebo; RAMRIQ synovitis score showed a least-squares mean change from baseline of -1417·0 μl (671·5) in the otilimab group and -912·3 μl (1405·8) with placebo. Compared with placebo, otilimab did not show significant reductions from baseline to week 12 in RAMRIS synovitis, osteitis and bone erosion, or in RAMRIQ synovitis and erosion damage. Adverse events were reported in 11 (39%) of 28 otilimab-treated and four (36%) of 11 placebo-treated patients, most commonly cough in the otilimab group (2 [7%] of 28; not reported in placebo group), and pain in extremity (four [36%] of 11) and rheumatoid arthritis (two [18%] of 11) in the placebo group (not reported in otilimab group). There were no serious adverse events or deaths.

INTERPRETATION

Serum concentrations of GM-CSF-otilimab complex indicated that target engagement was achieved with initial weekly dosing, but not sustained with every other week dosing. CCL17 might be a pharmacodynamic biomarker for otilimab activity in future studies. Otilimab was well tolerated and, despite suboptimal exposure, showed some evidence for improved synovitis over 12 weeks in patients with active rheumatoid arthritis.

FUNDING

GlaxoSmithKline.

GM-CSF: A Promising Target in Inflammation and Autoimmunity

The cytokine, granulocyte macrophage-colony stimulating factor (GM-CSF), was firstly identified as being able to induce in vitro the proliferation and differentiation of bone marrow progenitors into granulocytes and macrophages. Much preclinical data have indicated that GM-CSF has a wide range of functions across different tissues in its action on myeloid cells, and GM-CSF deletion/depletion approaches indicate its potential as an important therapeutic target in several inflammatory and autoimmune disorders, for example, rheumatoid arthritis. In this review, we discuss briefly the biology of GM-CSF, raise some current issues and questions pertaining to this biology, summarize the results from preclinical models of a range of inflammatory and autoimmune disorders and list the latest clinical trials evaluating GM-CSF blockade in such disorders.

Subsets of CD1c+ DCs: Dendritic Cell Versus Monocyte Lineage

Currently three bona fide dendritic cell (DC) types are distinguished in human blood. Herein we focus on type 2 DCs (DC2s) and compare the three defining markers CD1c, CD172, and CD301. When using CD1c to define DC2s, a CD14⁺ and a CD14⁻ subset can be detected. The CD14⁺ subset shares features with monocytes, and this includes substantially higher expression levels for CD64, CD115, CD163, and S100A8/9. We review the current knowledge of these CD1c⁺CD14⁺ cells as compared to the CD1c⁺CD14⁻ cells with respect to phenotype, function, transcriptomics, and ontogeny. Here, we discuss informative mutations, which suggest that two populations have different developmental requirements. In addition, we cover subsets of CD11c⁺CD8⁻ DC2s in the mouse, where CLEC12A⁺ESAM^low cells, as compared to the CLEC12A⁻ESAM^high subset, also express higher levels of monocyte-associated markers CD14, CD3, and CD115. Finally, we summarize, for both man and mouse, the data on lower antigen presentation and higher cytokine production in the monocyte-marker expressing DC2 subset, which demonstrate that the DC2 subsets are also functionally distinct.

Systemic and CNS Inflammation Crosstalk: Implications for Alzheimer's Disease

After years of failed therapeutic attempts targeting beta-amyloid (Aβ) in AD, there is now increasing evidence suggesting that inflammation holds a pivotal role in AD pathogenesis and immune pathways can possibly comprise primary therapeutic targets. Inflammation is a key characteristic of numerous diseases including neurodegenerative disorders and thus not surprisingly suppression of inflammation frequently constitutes a major therapeutic strategy for a wide spectrum of disorders. Several brain-resident and peripherally-derived immune populations and inflammatory mediators are involved in AD pathophysiology, with microglia comprising central cellular player in the disease process. Systemic inflammation, mostly in the form of infections, has long been observed to induce behavioral alterations and cognitive dysfunction, suggesting for a close interaction of the peripheral immune system with the brain. Systemic inflammation can result in neuroinflammation, mainly exhibited as microglial activation, production of inflammatory molecules, as well as recruitment of peripheral immune cells in the brain, thus shaping a cerebral inflammatory milieu that may seriously impact neuronal function. Increasing clinical and experimental studies have provided significant evidence that acute (e.g. infections) or chronic (e.g. autoimmune diseases like rheumatoid arthritis) systemic inflammatory conditions may be associated with increased AD risk and accelerate AD progression. Here we review the current literature that links systemic with CNS inflammation and the implications of this interaction for AD in the context of acute and chronic systemic pathologies as acute infection and rheumatoid arthritis. Elucidating the mechanisms that govern the crosstalk between the peripheral and the local brain immune system may provide the ground for new therapeutic approaches that target the immune-brain interface and shed light on the understanding of AD.

Update on the Pathomechanism, Diagnosis, and Treatment Options for Rheumatoid Arthritis

Rheumatoid arthritis (RA) is an autoimmune disease that involves multiple joints bilaterally. It is characterized by an inflammation of the tendon (tenosynovitis) resulting in both cartilage destruction and bone erosion. While until the 1990s RA frequently resulted in disability, inability to work, and increased mortality, newer treatment options have made RA a manageable disease. Here, great progress has been made in the development of disease-modifying anti-rheumatic drugs (DMARDs) which target inflammation and thereby prevent further joint damage. The available DMARDs are subdivided into (1) conventional synthetic DMARDs (methotrexate, hydrochloroquine, and sulfadiazine), (2) targeted synthetic DMARDs (pan-JAK- and JAK1/2-inhibitors), and (3) biologic DMARDs (tumor necrosis factor (TNF)-α inhibitors, TNF-receptor (R) inhibitors, IL-6 inhibitors, IL-6R inhibitors, B cell depleting antibodies, and inhibitors of co-stimulatory molecules). While DMARDs have repeatedly demonstrated the potential to greatly improve disease symptoms and prevent disease progression in RA patients, they are associated with considerable side-effects and high financial costs. This review summarizes our current understanding of the underlying pathomechanism, diagnosis of RA, as well as the mode of action, clinical benefits, and side-effects of the currently available DMARDs.

The Pleiotropic Effects of the GM-CSF Rheostat on Myeloid Cell Differentiation and Function: More Than a Numbers Game

Granulocyte Macrophage-Colony Stimulating Factor (GM-CSF) is a myelopoietic growth factor that has pleiotropic effects not only in promoting the differentiation of immature precursors into polymorphonuclear neutrophils (PMNs), monocytes/macrophages (MØs) and dendritic cells (DCs), but also in controlling the function of fully mature myeloid cells. This broad spectrum of GM-CSF action may elicit paradoxical outcomes-both immunostimulation and immunosuppression-in infection, inflammation, and cancer. The complexity of GM-CSF action remains to be fully unraveled. Several aspects of GM-CSF action could contribute to its diverse biological consequences. Firstly, GM-CSF as a single cytokine affects development of most myeloid cells from progenitors to mature immune cells. Secondly, GM-CSF activates JAK2/STAT5 and also activate multiple signaling modules and transcriptional factors that direct different biological processes. Thirdly, GM-CSF can be produced by different cell types including tumor cells in response to different environmental cues; thus, GM-CSF quantity can vary greatly under different pathophysiological settings. Finally, GM-CSF signaling is also fine-tuned by other less defined feedback mechanisms. In this review, we will discuss the role of GM-CSF in orchestrating the differentiation, survival, and proliferation during the generation of multiple lineages of myeloid cells (PMNs, MØs, and DCs). We will also discuss the role of GM-CSF in regulating the function of DCs and the functional polarization of MØs. We highlight how the dose of GM-CSF and corresponding signal strength acts as a rheostat to fine-tune cell fate, and thus the way GM-CSF may best be targeted for immuno-intervention in infection, inflammation and cancer.

Mavrilimumab: a unique insight and update on the current status in the treatment of rheumatoid arthritis

Introduction: Rheumatoid arthritis (RA) is a chronic, systemic, autoimmune disease, which affects joints and extra-articular structures. Nowadays, the armamentarium of therapeutic options is progressively expanding and embraces several mechanisms of action: TNF inhibition, B-cell depletion, T-cell co-stimulation inhibition, IL-6 blockade, and JAK-inhibition. Granulocyte-Monocyte-Colony-Stimulating-Factor (GM-CSF) is a mediator acting as a cytokine with a proven pathogenetic role in RA, providing a potential alternative target for the management of the disease. Mavrilimumab is a monoclonal antibody against GM-CSF receptor, which has been successfully tested in RA patients. Areas covered: Beginning with a description of the preclinical evidence and the rationale for GM-CSF blockade in RA, this review will provide a wide overview of mavrilimumab efficacy and safety profile by analyzing phase I/II RCTs conducted in patients with moderate to severe RA. Expert opinion: According to the promising results from phase I-II RCTs, mavrilimumab could be considered as an additional therapeutic option for RA patients multi-resistant to the available targeted drugs. However, the optimal dose and the profile of this new drug should be confirmed in phase III RCTs before the marketing.

Efficacy and safety of namilumab, a human monoclonal antibody against granulocyte-macrophage colony-stimulating factor (GM-CSF) ligand in patients with rheumatoid arthritis (RA) with either an inadequate response to background methotrexate therapy or an inadequate response or intolerance to an anti-TNF (tumour necrosis factor) biologic therapy: a randomized, controlled trial

Background

Namilumab (AMG203), an immunoglobulin G1 monoclonal antibody that binds with high affinity to granulocyte-macrophage colony-stimulating factor (GM-CSF), was evaluated in a phase II randomized, double-blind, placebo-controlled study to investigate the efficacy and safety in patients with rheumatoid arthritis (RA) with an inadequate response to methotrexate (MTX-IR) or anti-tumour necrosis factor therapy (TNF-IR).

Methods

Subcutaneous namilumab (20, 80, or 150 mg) or placebo was administered at baseline and weeks 2, 6, and 10 in patients on stable background methotrexate therapy who were with MTX-IR or TNF-IR. Primary endpoint was mean change from baseline in the 28-joint Disease Activity Score, C-reactive protein version (DAS28-CRP) at week 12 comparing each of the three doses of namilumab to placebo. Safety and tolerability were assessed by adverse events (AEs) and pulmonary parameters. Results were analysed using the per-protocol population.

Results

One hundred eight patients from Europe and Japan (48.4 ± 12.02 years old; 77.8% female; mean DAS28-CRP 5.60–5.79; rheumatoid factor/anti-citrullinated protein antibodies + 75%) were randomized to placebo or namilumab 20, 80, or 150 mg (n = 27, 28, 25, and 28, respectively). Ninety-two were MTX-IR; 16 were TNF-IR. At week 12, a statistically significant difference in DAS28-CRP (p = 0.005) was seen for namilumab 150 mg versus placebo and separation was seen as early as week 2 for namilumab 150 mg (p < 0.05), with higher ACR50 and response rates versus placebo at week 12. A dose-response effect was observed across the DAS28-CRP endpoint with separation versus placebo evident from week 2. The most common treatment-emergent AEs were nasopharyngitis (18.5%, 17.9%, 4.0%, 14.3%), dyspnoea (0.0%, 3.6%, 8.0%, 10.7%), bronchitis (7.4%, 3.6%, 4.0%, 3.6%), and headache (3.7%, 3.6%, 12.0%, 0.0%) for placebo and 20, 80, or 150 mg of namilumab, respectively. No serious infections were observed. One serious AE (myocardial infarction) was observed with 150 mg of namilumab. There was no apparent dose relationship for AEs. A biomarker-based disease activity score showed a dose-dependent decrease at week 12.

Conclusions

This phase II study demonstrates the benefit of inhibiting macrophage activity targeting the GM-CSF for RA. The study met its primary endpoint with a clear dose-response effect. An acceptable tolerability profile was demonstrated over the 12-week study.

Trial registration

ClinicalTrials.gov, NEXUS; NCT02379091, submitted November 28, 2014

Electronic supplementary material

The online version of this article (10.1186/s13075-019-1879-x) contains supplementary material, which is available to authorized users.

Granulocyte-macrophage colony-stimulating factor inactivation in CAR T-cells prevents monocyte-dependent release of key cytokine release syndrome mediators

Chimeric antigen receptor T-cell (CAR T-cell) therapy has been shown to be clinically effective for managing a variety of hematological cancers. However, CAR T-cell therapy is associated with multiple adverse effects, including neurotoxicity and cytokine release syndrome (CRS). CRS arises from massive cytokine secretion and can be life-threatening, but it is typically managed with an anti-IL-6Ra mAb or glucocorticoid administration. However, these treatments add to a patient's medication burden and address only the CRS symptoms. Therefore, alternative strategies that can prevent CRS and neurotoxicity associated with CAR T-cell treatment are urgently needed. Here, we explored a therapeutic route aimed at preventing CRS rather than limiting its consequences. Using a cytokine-profiling assay, we show that granulocyte-macrophage colony-stimulating factor (GMCSF) is a key CRS-promoting protein. Through a combination of in vitro experiments and gene-editing technology, we further demonstrate that antibody-mediated neutralization or TALEN-mediated genetic inactivation of GMCSF in CAR T-cells drastically decreases available GMCSF and abolishes macrophage-dependent secretion of CRS biomarkers, including monocyte chemoattractant protein 1 (MCP-1), interleukin (IL) 6, and IL-8. Of note, we also found that the genetic inactivation of GMCSF does not impair the antitumor function or proliferative capacity of CAR T-cells in vitro We conclude that it is possible to prevent CRS by using "all-in-one" GMCSF-knockout CAR T-cells. This approach may eliminate the need for anti-CRS treatment and may improve the overall safety of CAR T-cell therapies for cancer patients.

Innate Immune Modulation by GM-CSF and IL-3 in Health and Disease

Granulocyte-macrophage colony-stimulating factor (GM-CSF) and inteleukin-3 (IL-3) have long been known as mediators of emergency myelopoiesis, but recent evidence has highlighted their critical role in modulating innate immune effector functions in mice and humans. This new wealth of knowledge has uncovered novel aspects of the pathogenesis of a range of disorders, including infectious, neoplastic, autoimmune, allergic and cardiovascular diseases. Consequently, GM-CSF and IL-3 are now being investigated as therapeutic targets for some of these disorders, and some phase I/II clinical trials are already showing promising results. There is also pre-clinical and clinical evidence that GM-CSF can be an effective immunostimulatory agent when being combined with anti-cytotoxic T lymphocyte-associated protein 4 (anti-CTLA-4) in patients with metastatic melanoma as well as in novel cancer immunotherapy approaches. Finally, GM-CSF and to a lesser extent IL-3 play a critical role in experimental models of trained immunity by acting not only on bone marrow precursors but also directly on mature myeloid cells. Altogether, characterizing GM-CSF and IL-3 as central mediators of innate immune activation is poised to open new therapeutic avenues for several immune-mediated disorders and define their potential in the context of immunotherapies.

IL-17 in Rheumatoid Arthritis and Precision Medicine: From Synovitis Expression to Circulating Bioactive Levels

Interleukin (IL)-17A has a direct contribution in early induction and late chronic stages of various inflammatory diseases. In vitro and in vivo experiments have first characterized its local effects on different cell types and then its systemic effects. For instance, IL-17 axis is now identified as a key driver of psoriasis through its effects on keratinocytes. Similar observations apply for rheumatoid arthritis (RA) where IL-17A triggers changes in the synovium that lead to synovitis and maintain local inflammation. These results have prompted the development of biologics to target this cytokine. However, while convincing studies are reported on the efficacy of IL-17 inhibitors in psoriasis, there are conflicting results in RA. Patient heterogeneity but also the involvement of mediators that regulate IL-17 function may explain these results. Therefore, new tools and concepts are required to identify patients that could benefit from these IL-17 targeted therapies in RA and the development of predictive biomarkers of response has started with the emergence of various bioassays. Current strategies are also focusing on synovial biopsies that may be used to stratify patients. From local to systemic levels, new approaches are developing and move the field of RA management into the era of precision medicine.

Clinical, immunological and microbial gingival profile of juvenile systemic lupus erythematosus patients

Periodontal disease has been associated with rheumatic diseases; however, few studies have evaluated the association with systemic lupus erythematosus (SLE), and its impact on the local inflammatory and microbial profiles. Therefore, this study evaluated the levels of several cytokines in gingival crevicular fluid (GCF) and serum from juvenile SLE (jSLE) patients with gingival inflammation, compared with controls. In addition, we assessed their subgingival microbial profile. Thirty jSLE patients and 29 systemically healthy individuals were recruited. Participants were rheumatologically and periodontally examined, and GCF, serum and intrasulcular biofilm were collected. Cytokines were analysed by bead-based multiplex assays and the bacterial profile by checkerboard DNA-DNA hybridization. jSLE patients presented higher percentages of dental plaque and bleeding than controls, as well as increased mean probing depth and attachment loss. After adjustment for multiple comparisons, GCF levels of interleukin (IL)-1β, IL-8, granulocyte colony-stimulating factor (G-CSF), interferon-γ and monocyte chemoattractant protein-1 were significantly higher, whereas the levels of granulocyte-macrophage colony-stimulating factor were significantly lower in jSLE patients. In serum, G-CSF levels tended to be higher in jSLE patients (adjusted p-value = 0.06). Intrasulcular counts of Aggregatibacter actinomycetemcomitans were significantly higher in jSLE patients as compared with controls. We conclude that patients with jSLE present a worse periodontal condition associated with altered levels of pro-inflammatory cytokines in GCF and increased counts of A. actinomycetemcomitans in the intrasulcular biofilm.

GM-CSF Quantity Has a Selective Effect on Granulocytic vs. Monocytic Myeloid Development and Function

GM-CSF promotes myeloid differentiation of cultured bone marrow cells into cells of the granulocytic and monocytic lineage; the latter can further differentiate into monocytes/macrophages and dendritic cells. How GM-CSF selects for these different myeloid fates is unresolved. GM-CSF levels can change either iatrogenically (e.g., augmenting leukopoiesis after radiotherapy) or naturally (e.g., during infection or inflammation) resulting in different immunological outcomes. Therefore, we asked whether the dose of GM-CSF may regulate the development of three types of myeloid cells. Here, we showed that GM-CSF acted as a molecular rheostat where the quantity determined which cell type was favored; moreover, the cellular process by which this was achieved was different for each cell type. Thus, low quantities of GM-CSF promoted the granulocytic lineage, mainly through survival. High quantities promoted the monocytic lineage, mainly through proliferation, whereas moderate quantities promoted moDCs, mainly through differentiation. Finally, we demonstrated that monocytes/macrophages generated with different doses of GM-CSF differed in function. We contend that this selective effect of GM-CSF dose on myeloid differentiation and function should be taken into consideration during pathophysiological states that may alter GM-CSF levels and during GM-CSF agonistic or antagonistic therapy.

Investigational therapies targeting the granulocyte macrophage colony-stimulating factor receptor-α in rheumatoid arthritis: focus on mavrilimumab

Mavrilimumab (formerly CAM-3001) is a high-affinity, immunoglobulin G4 monoclonal antibody (mAb) against the granulocyte macrophage colony-stimulating factor (GM-CSF) receptor-α chain. Phase I and II trials in patients with rheumatoid arthritis (RA) treated with mavrilimumab have shown encouraging results with respect to both safety and efficacy. No significant adverse events have so far been noted. The trials have demonstrated significant clinical benefit, meeting primary endpoints. Furthermore, for RA patients treated with mavrilimumab, who were tumour necrosis factor (TNF) inhibitor-inadequate responders, there are encouraging preliminary data indicating benefit and identifying potential biomarkers predictive of patients likely to find benefit. Here, we review the clinical trial data for mavrilimumab and discuss its potential as a treatment for RA in light of the competitive landscape in which it resides.

Increased Frequency of Peripheral B and T Cells Expressing Granulocyte Monocyte Colony-Stimulating Factor in Rheumatoid Arthritis Patients

Objectives

Granulocyte monocyte colony-stimulating factor (GM-CSF) is currently considered a crucial inflammatory mediator and a novel therapeutic target in rheumatoid arthritis (RA), despite the fact that its precise cellular sources remain uncertain. We studied the expression of GM-CSF in peripheral lymphocytes from RA patients and its change with antirheumatic therapies.

Methods

Intracellular GM-CSF expression was assessed by flow cytometry in stimulated peripheral B (CD19+) and T (CD3+) cells from RA patients (n = 40), disease (n = 31 including osteoarthritis n = 15, psoriatic arthritis n = 10, and systemic rheumatic diseases n = 6) and healthy (n = 16) controls. The phenotype of GM-CSF+ B cells was assessed as well as longitudinal changes in GM-CSF+ lymphocytes during methotrexate (MTX, n = 10) or anti-tumor necrosis factor (anti-TNF, n = 10) therapy.

Results

Among untreated RA patients with active disease (Disease Activity Score 28-C-reactive protein = 5.6 ± 0.89) an expanded population of peripheral GM-CSF+ B (4.1 ± 2.2%) and T (3.4 ± 1.6%) cells was detected compared with both disease (1.7 ± 0.9%, p < 0.0001 and 1.7 ± 1.3%, p < 0.0001, respectively) and healthy (0.3 ± 0.2%, p < 0.0001 and 0.6 ± 0.6%, p < 0.0001) controls. RA GM-CSF+ B cells displayed more commonly a plasmablast or transitional phenotype (37.12 ± 18.34% vs. 14.26 ± 9.46%, p = 0.001 and 30.49 ± 15.04% vs. 2.45 ± 1.84%, p < 0.0001, respectively) and less a memory phenotype (21.46 ± 20.71% vs. 66.99 ± 16.63%, p < 0.0001) compared to GM-CSF- cells. GM-CSF expression in RA patients did not correlate to disease duration, activity or serological status. Anti-TNF treatment led to a statistically significant decrease in GM-CSF+ B and T cells while MTX had no significant effect.

Discussion

This is the first study showing an expanded population of GM-CSF+ B and T lymphocytes in patients with active RA which declined after anti-TNF therapy.

Dysregulation of the Cytokine GM-CSF Induces Spontaneous Phagocyte Invasion and Immunopathology in the Central Nervous System

Chronic inflammatory diseases are influenced by dysregulation of cytokines. Among them, granulocyte macrophage colony stimulating factor (GM-CSF) is crucial for the pathogenic function of T cells in preclinical models of autoimmunity. To study the impact of dysregulated GM-CSF expression in vivo, we generated a transgenic mouse line allowing the induction of GM-CSF expression in mature, peripheral helper T (Th) cells. Antigen-independent GM-CSF release led to the invasion of inflammatory myeloid cells into the central nervous system (CNS), which was accompanied by the spontaneous development of severe neurological deficits. CNS-invading phagocytes produced reactive oxygen species and exhibited a distinct genetic signature compared to myeloid cells invading other organs. We propose that the CNS is particularly vulnerable to the attack of monocyte-derived phagocytes and that the effector functions of GM-CSF-expanded myeloid cells are in turn guided by the tissue microenvironment.

Anti-TNF Therapy

Tumor necrosis factor (TNF) is one of the most important cytokines produced by macrophages. TNF is a very important component of host defense, released very rapidly after all types of injuries and stimuli. The kinetics of TNF release are short, and so it is perhaps not surprising that prolonged TNF production is associated with pathology. This was first elucidated in rheumatoid arthritis but extends to other chronic inflammatory diseases such as Crohn's disease and psoriasis. In this chapter, the discovery of anti-TNF therapy is reviewed, with its benefit but also its limitations. The potential of anti-TNF therapy in other diseases, e.g., cardiovascular and fibrosis, is discussed, as is the opportunity to define ways of blocking TNF synthesis.

Phase 1b randomized, double-blind study of namilumab, an anti-granulocyte macrophage colony-stimulating factor monoclonal antibody, in mild-to-moderate rheumatoid arthritis

Background

Namilumab (AMG203) is an immunoglobulin G1 monoclonal antibody that binds with high affinity to the GM-CSF ligand. This was a phase 1b, randomized, double-blind study (PRIORA) to assess namilumab in active, mild-to-moderate rheumatoid arthritis (RA). The primary outcome was the safety and tolerability of repeated subcutaneous injections of namilumab in patients with mild-to-moderate RA.

Methods

Adults with mild-to-moderate RA on stable methotrexate doses for ≥12 weeks were eligible. Patients received three subcutaneous injections of namilumab 150 or 300 mg, or placebo on days 1, 15, and 29, with 12 weeks’ follow-up. Primary objective was safety/tolerability.

Results

Patients in cohort 1 were randomized to namilumab 150 mg (n = 8) or placebo (n = 5). In cohort 2, patients were randomized to namilumab 300 mg (n = 7) or placebo (n = 4). Incidence of treatment-emergent adverse events (TEAEs) was similar across the three groups (namilumab 150 mg: 63%; namilumab 300 mg: 57%; placebo: 56%). TEAEs in ≥10% of patients were nasopharyngitis (17%) and exacerbation/worsening of RA (13%). No anti-namilumab antibodies were detected. The pharmacokinetics of namilumab were linear and typical of a monoclonal antibody with subcutaneous administration. In a post hoc efficacy, per protocol analysis (n = 21), patients randomized to namilumab showed greater improvement in Disease Activity Score 28 (erythrocyte sedimentation rate and C-reactive protein [CRP]), swelling joint counts and tender joint counts compared with placebo. Difference in mean DAS28-CRP changes from baseline between namilumab and placebo favored namilumab at both doses and at all time points. In addition area under the curve for DAS28-CRP was analyzed as time-adjusted mean change from baseline. A significant improvement in DAS28-CRP was shown with namilumab (150 and 300 mg groups combined) compared with placebo at day 43 (p = 0.0117) and also 8 weeks after last dosing at day 99 (p = 0.0154).

Conclusions

Subcutaneous namilumab was generally well tolerated. Although namilumab demonstrated preliminary evidence of efficacy, patient numbers were small; phase 2 studies are ongoing.

Trial registration

ClinicalTrials.gov, NCT01317797. Registered 18 February 2011.

Electronic supplementary material

The online version of this article (doi:10.1186/s13075-017-1267-3) contains supplementary material, which is available to authorized users.

Spotlight on mavrilimumab for the treatment of rheumatoid arthritis: evidence to date

The introduction of biological therapies into clinical practice has dramatically modified the natural history of chronic inflammatory diseases, such as rheumatoid arthritis (RA). RA is a systemic autoimmune disease that causes articular damage and has a great negative impact on patients’ quality of life. Despite the wide spectrum of available biological treatments, ~30% of RA patients are still unresponsive, resulting in high disability and increased morbidity and mortality. In the last few decades, the scientific knowledge on RA pathogenesis vastly improved, leading to the identification of new proinflammatory molecules as potential therapeutic targets. Several in vitro and in vivo studies showed that granulocyte-macrophage colony-stimulating factor (GM-CSF), known to be a hematopoietic factor, is also one of the proinflammatory cytokines involved in macrophage activation, crucial for the pathogenic network of RA. Mavrilimumab, a human monoclonal antibody targeting the subunit α of GM-CSF receptor, was recently developed as a competitive antagonist of GM-CSF pathway and successfully adopted in human trials for mild to moderate RA. Mavrilimumab phase I and phase II studies reported an overall good efficacy and safety profile of the drug, and these encouraging results promoted the initiation of worldwide phase III studies. In particular, 158-week results of phase II trials did not show long-term lung toxicity, addressing the major concern about this target of pulmonary alveolar proteinosis development. However, further clinical studies conducted in larger RA populations are needed to confirm these promising results. This review summarizes the biological role of GM-CSF in RA and the preclinical and clinical data on mavrilimumab and other monoclonal antibodies targeted on this pathway as an alternative therapeutic option in RA patients who are unresponsive to conventional biological drugs.

Novel GM-CSF-based vaccines: One small step in GM-CSF gene optimization, one giant leap for human vaccines

Granulocyte macrophage-colony stimulating factor (GM-CSF) is a potent immunomodulatory cytokine that is known to facilitate vaccine efficacy by promoting the development and prolongation of both humoral and cellular immunity. In the past years we have generated a novel codon-optimized GM-CSF gene as an adjuvant. The codon-optimized GM-CSF gene significantly increased protein expression levels in all cells tested and helped in generating a strong immune responses against HIV-1 Gag and HPV-associated cancer. Here, we review the literature dealing with the adjuvant activity of GM-CSF both in animal models and clinical trials. We anticipate that the codon-optimized GM-CSF gene offers a practical molecular strategy for potentiating immune responses to tumor cell-based vaccinations as well as other immunotherapeutic strategies.

Granulocyte macrophage colony-stimulating factor induces CCL17 production via IRF4 to mediate inflammation

Data from preclinical and clinical studies have demonstrated that granulocyte macrophage colony-stimulating factor (GM-CSF) can function as a key proinflammatory cytokine. However, therapies that directly target GM-CSF function could lead to undesirable side effects, creating a need to delineate downstream pathways and mediators. In this work, we provide evidence that GM-CSF drives CCL17 production by acting through an IFN regulatory factor 4-dependent (IRF4-dependent) pathway in human monocytes, murine macrophages, and mice in vivo. In murine models of arthritis and pain, IRF4 regulated the formation of CCL17, which mediated the proinflammatory and algesic actions of GM-CSF. Mechanistically, GM-CSF upregulated IRF4 expression by enhancing JMJD3 demethylase activity. We also determined that CCL17 has chemokine-independent functions in inflammatory arthritis and pain. These findings indicate that GM-CSF can mediate inflammation and pain by regulating IRF4-induced CCL17 production, providing insights into a pathway with potential therapeutic avenues for the treatment of inflammatory diseases and their associated pain.

GM-CSF as a therapeutic target in autoimmune diseases

Granulocyte-macrophage colony-stimulating factor (GM-CSF) has been known as a hematopoietic growth factor and immune modulator. Recent studies revealed that GM-CSF also had pro-inflammatory functions and contributed to the pathogenicity of Th17 cells in the development of Th17-mediated autoimmune diseases. GM-CSF inhibition in some animal models of autoimmune diseases showed significant beneficial effects. Therefore, several agents targeting GM-CSF are being developed and are expected to be a useful strategy for the treatment of autoimmune diseases. Particularly, in clinical trials for rheumatoid arthritis (RA) patients, GM-CSF inhibition showed rapid and significant efficacy with no serious side effects. This article summarizes recent findings of GM-CSF and information of clinical trials targeting GM-CSF in autoimmune diseases.

Targeting GM-CSF in inflammatory diseases

Granulocyte-macrophage colony stimulating factor (GM-CSF) is a growth factor first identified as an inducer of differentiation and proliferation of granulocytes and macrophages derived from haematopoietic progenitor cells. Later studies have shown that GM-CSF is involved in a wide range of biological processes in both innate and adaptive immunity, with its production being tightly linked to the response to danger signals. Given that the functions of GM-CSF span multiple tissues and biological processes, this cytokine has shown potential as a new and important therapeutic target in several autoimmune and inflammatory disorders - particularly in rheumatoid arthritis. Indeed, GM-CSF was one of the first cytokines detected in human synovial fluid from inflamed joints. Therapies that target GM-CSF or its receptor have been tested in preclinical studies with promising results, further supporting the potential of targeting the GM-CSF pathway. In this Review, we discuss our expanding view of the biology of GM-CSF, outline what has been learnt about GM-CSF from studies of animal models and human diseases, and summarize the results of early phase clinical trials evaluating GM-CSF antagonism in inflammatory disorders.

Honokiol possesses potential anti-inflammatory effects on rheumatoid arthritis and GM-CSF can be a target for its treatment

OBJECTIVE

To observe the anti-inflammatory effects of honokiol in primary cultures of peripheral blood mononuclear cells of rheumatoid arthritis patients, the pro-inflammatory cytokines and potential targets were investigated.

METHODS

The levels of GM-CSF, IL-1β, TNF-α and IL-8 were determined by ELISA assay. The genes and proteins expression were analyzed by real-time PCR and Western blotting respectively.

RESULTS

The serum IL-1β, TNF-α and GM-CSF levels were 1.76-, 2.16- and 3.57-fold increased in patients with RA as compared to those of control group. Honokiol inhibited the expression levels of IL-1β, TNF-α, GM-CSF and IL-8 in PBMCs with a dose-dependent manner. Measurements obtained from supernatants were positively correlated between TNF-α and IL-1β, moreover, similar results found TNF-α levels positively correlated with GM-CSF and IL-8 activity in the supernatants of PBMCs isolated from RA patients. Furthermore, the mRNA and protein expression of IL-1β, GM-CSF and IL-8 were up-regulated when the PBMCs exposure to TNF-α, however, honokiol treatment significantly reversed the expression of IL-1β, TNF-α and GM-CSF in response to TNF-α with a dose-dependent manner.

CONCLUSIONS

This study demonstrates that honokiol could possess potential anti-inflammatory effects and inhibits TNF-α-induced IL-1β, GM-CSF and IL-8 production in PBMCs from rheumatoid arthritis patients.

Pivotal roles of GM-CSF in autoimmunity and inflammation

Granulocyte macrophage-colony stimulating factor (GM-CSF) is a hematopoietic growth factor, which stimulates the proliferation of granulocytes and macrophages from bone marrow precursor cells. In autoimmune and inflammatory diseases, Th17 cells have been considered as strong inducers of tissue inflammation. However, recent evidence indicates that GM-CSF has prominent proinflammatory functions and that this growth factor (not IL-17) is critical for the pathogenicity of CD4⁺ T cells. Therefore, the mechanism of GM-CSF-producing CD4⁺ T cell differentiation and the role of GM-CSF in the development of autoimmune and inflammatory diseases are gaining increasing attention. This review summarizes the latest knowledge of GM-CSF and its relationship with autoimmune and inflammatory diseases. The potential therapies targeting GM-CSF as well as their possible side effects have also been addressed in this review.

IL-1β and TNFα promote monocyte viability through the induction of GM-CSF expression by rheumatoid arthritis synovial fibroblasts

BACKGROUND

Macrophages and synovial fibroblasts (SF) are two major cells implicated in the pathogenesis of rheumatoid arthritis (RA). SF could be a source of cytokines and growth factors driving macrophages survival and activation. Here, we studied the effect of SF on monocyte viability and phenotype.

METHODS

SF were isolated from synovial tissue of RA patients and CD14+ cells were isolated from peripheral blood of healthy donors. SF conditioned media were collected after 24 hours of culture with or without stimulation with TNFα or IL-1β. Macrophages polarisation was studied by flow cytometry.

RESULTS

Conditioned medium from SF significantly increased monocytes viability by 60% compared to CD14+ cells cultured in medium alone (P < 0.001). This effect was enhanced using conditioned media from IL-1β and TNFα stimulated SF. GM-CSF but not M-CSF nor IL34 blocking antibodies was able to significantly decrease monocyte viability by 30% when added to the conditioned media from IL-1β and TNFα stimulated SF (P < 0.001). Finally, monocyte cultured in presence of SF conditioned media did not exhibit a specific M1 or M2 phenotype.

CONCLUSION

Overall, rheumatoid arthritis synovial fibroblasts stimulated with proinflammatory cytokines (IL-1β and TNFα) promote monocyte viability via GM-CSF but do not induce a specific macrophage polarization.

Fc gamma receptor IIb on GM-CSF macrophages controls immune complex mediated inhibition of inflammatory signals

BACKGROUND

In rheumatoid arthritis (RA) macrophages play a major role in amplifying synovial inflammation. Important activating signals are those induced by Toll-like receptor (TLR) ligands and by activated T cells. The balance between activating and inhibitory Fc gamma receptors (FcγRs) on macrophages might be crucial in modulating these inflammatory responses. The purpose of this study was to determine FcγR expression on pro- and anti-inflammatory macrophages (gmMφ and mMφ, respectively) and identify functional consequences on immune complex uptake and macrophage activation.

METHODS

Human monocytes were isolated and differentiated into gmMφ and mMφ. A full FcγR characterization of both macrophage subtypes was performed and uptake of fluorescent immune complexes (ICs) was determined. FcγRIIb isoforms were determined by qPCR. Macrophages were stimulated via different TLRs or cytokine activated T cells in the presence or absence of ICs and cytokine production was determined. Blocking studies were performed to look into the pathways involved.

RESULTS

mMφ expressed high levels of the activating FcγRIIa and FcγRIII and low levels of the inhibitory FcγRIIb, while the FcγR balance on gmMφ was shifted towards the inhibitory FcγRIIb. This was accompanied by a clear increase in FcγRIIb1 mRNA expression in gmMφ. This resulted in higher IC uptake by mMφ compared to gmMφ. Furthermore, FcγR-mediated stimulation of gmMφ inhibited TLR2, 3, 4 and 7/8 mediated cytokine production via FcγRIIb and PI3K signaling. In addition, gmMφ but not mMφ produced TNFα upon co-culture with cytokine activated T cells, which was reduced by IC binding to FcγRIIb. The latter was dependent on PI3K signaling and COX2.

CONCLUSIONS

FcγR expression patterns on gmMφ and mMφ are significantly different, which translates in clear functional differences further substantiating FcγRIIb as an interesting target for inflammation control in RA and other autoimmune/inflammatory diseases.

Identification of rheumatoid arthritis and osteoarthritis patients by transcriptome-based rule set generation

INTRODUCTION

Discrimination of rheumatoid arthritis (RA) patients from patients with other inflammatory or degenerative joint diseases or healthy individuals purely on the basis of genes differentially expressed in high-throughput data has proven very difficult. Thus, the present study sought to achieve such discrimination by employing a novel unbiased approach using rule-based classifiers.

METHODS

Three multi-center genome-wide transcriptomic data sets (Affymetrix HG-U133 A/B) from a total of 79 individuals, including 20 healthy controls (control group - CG), as well as 26 osteoarthritis (OA) and 33 RA patients, were used to infer rule-based classifiers to discriminate the disease groups. The rules were ranked with respect to Kiendl's statistical relevance index, and the resulting rule set was optimized by pruning. The rule sets were inferred separately from data of one of three centers and applied to the two remaining centers for validation. All rules from the optimized rule sets of all centers were used to analyze their biological relevance applying the software Pathway Studio.

RESULTS

The optimized rule sets for the three centers contained a total of 29, 20, and 8 rules (including 10, 8, and 4 rules for 'RA'), respectively. The mean sensitivity for the prediction of RA based on six center-to-center tests was 96% (range 90% to 100%), that for OA 86% (range 40% to 100%). The mean specificity for RA prediction was 94% (range 80% to 100%), that for OA 96% (range 83.3% to 100%). The average overall accuracy of the three different rule-based classifiers was 91% (range 80% to 100%). Unbiased analyses by Pathway Studio of the gene sets obtained by discrimination of RA from OA and CG with rule-based classifiers resulted in the identification of the pathogenetically and/or therapeutically relevant interferon-gamma and GM-CSF pathways.

CONCLUSION

First-time application of rule-based classifiers for the discrimination of RA resulted in high performance, with means for all assessment parameters close to or higher than 90%. In addition, this unbiased, new approach resulted in the identification not only of pathways known to be critical to RA, but also of novel molecules such as serine/threonine kinase 10.

Mavrilimumab: an evidence based review of its potential in the treatment of rheumatoid arthritis

Rheumatoid arthritis (RA) management has greatly improved with the development of biologic disease modifying antirheumatic drugs, but a proportion of patients do not improve despite the biologic drugs currently available. We need new biologic agents with novel mechanisms of action for the treatment of refractory patients. Recent evidence has shown that granulocyte-macrophage colony-stimulating factor (GM-CSF) is involved in the pathogenesis of RA. GM-CSF can exacerbate RA and elevated levels of this cytokine have been observed in synovial fluid from RA patients. Antagonism of GM-CSF can strikingly reduce established disease in mouse models of arthritis. Mavrilimumab, a human monoclonal antibody to GM-CSF receptor α, is a competitive antagonist of GM-CSF signaling. Phase I and II studies have shown good clinical response with a good safety profile in patients with mild to moderate RA, suggesting encouraging effects of mavrilimumab for the treatment of RA. This paper reviews the preclinical and clinical data evaluating the safety, tolerability, and efficacy of mavrilimumab in the treatment of RA.

GM-CSF alters dendritic cells in autoimmune diseases

Autoimmune diseases arise from an inappropriate immune response against self components, including macromolecules, cells, tissues, organs etc. They are often triggered or accompanied by inflammation, during which the levels of granulocyte macrophage colony-stimulating factor (GM-CSF) are elevated. GM-CSF is an inflammatory cytokine that has profound impact on the differentiation of immune system cells of myeloid lineage, especially dendritic cells (DCs) that play critical roles in immune initiation and tolerance, and is involved in the pathogenesis of autoimmune diseases. Although GM-CSF was discovered decades ago, recent studies with some new findings have shed an interesting light on the old hematopoietic growth factor. In the inflammatory autoimmune diseases, GM-CSF redirects the normal developmental pathway of DCs, conditions their antigen presentation capacities and endows them with unique cytokine signatures to affect autoimmune responses. Here we review the latest advances in the field, with the aim of demonstrating the effects of GM-CSF on DCs and their influences on autoimmune diseases. The summarized knowledge will help to design DC-based strategies for the treatment of autoimmune diseases.

Molecular control of steady-state dendritic cell maturation and immune homeostasis

Dendritic cells (DCs) are specialized sentinels responsible for coordinating adaptive immunity. This function is dependent upon coupled sensitivity to environmental signs of inflammation and infection to cellular maturation-the programmed alteration of DC phenotype and function to enhance immune cell activation. Although DCs are thus well equipped to respond to pathogens, maturation triggers are not unique to infection. Given that immune cells are exquisitely sensitive to the biological functions of DCs, we now appreciate that multiple layers of suppression are required to restrict the environmental sensitivity, cellular maturation, and even life span of DCs to prevent aberrant immune activation during the steady state. At the same time, steady-state DCs are not quiescent but rather perform key functions that support homeostasis of numerous cell types. Here we review these functions and molecular mechanisms of suppression that control steady-state DC maturation. Corruption of these steady-state operatives has diverse immunological consequences and pinpoints DCs as potent drivers of autoimmune and inflammatory disease.

Suppression of dendritic cell maturation and T cell proliferation by synovial fluid myeloid cells from mice with autoimmune arthritis

OBJECTIVE

To determine whether myeloid cells (such as granulocytes) present in the synovial fluid (SF) of arthritic joints have an impact on adaptive immunity. Specifically, we investigated the effects of SF cells harvested from the joints of mice with proteoglycan-induced arthritis (PGIA), on dendritic cell (DC) maturation and antigen-specific T cell proliferation.

METHODS

We monitored DC maturation (MHCII and CD86 expression) by flow cytometry upon coculture of DCs with SF cells or spleen myeloid cells from mice with PGIA. The effects of these myeloid cells on T cell proliferation were studied using T cells purified from PG-specific T cell receptor (TCR)-transgenic (Tg) mice. Phenotype analysis of myeloid cells was performed by immunostaining, reverse transcription-polymerase chain reaction, Western blotting, and biochemical assays.

RESULTS

Inflammatory SF cells significantly suppressed the maturation of DCs upon coculture. PG-TCR-Tg mouse T cells cultured with antigen-loaded DCs showed dramatic decreases in proliferation in the presence of SF cells. Spleen myeloid cells from arthritic mice did not have suppressive effects. SF cells were unable to suppress CD3/CD28-stimulated proliferation of the same T cells, suggesting a DC-dependent mechanism. SF cells exhibited all of the characteristics of myeloid-derived suppressor cells (MDSCs) and exerted suppression primarily through the production of nitric oxide and reactive oxygen species by granulocyte-like cells.

CONCLUSION

SF in the joints of mice with PGIA contains a population of granulocytic MDSCs that potently suppress DC maturation and T cell proliferation. These MDSCs have the potential to limit the expansion of autoreactive T cells, thus breaking the vicious cycle of autoimmunity and inflammation.

Mavrilimumab, a human monoclonal GM-CSF receptor-α antibody for the management of rheumatoid arthritis: a novel approach to therapy

INTRODUCTION

Mavrilimumab , formerly known as CAM-3001, a GM-CSF receptor-α antibody, is the first human monoclonal antibody to be used in Phase II studies (2011) to modulate the innate immunity pathway targeting GM-CSF signaling in moderate rheumatoid arthritis (RA).

AREAS COVERED

Analysis of available clinical trial data on GM-CSF receptor-α antibody and medical literature search using MEDLINE for molecular mechanisms of pathogenesis of RA and its treatment forms the basis of this expert opinion review. The mavrilimumab Phase II double blind, randomized, placebo-controlled ascending dose trial demonstrated statistically significant achievement of primary and secondary end points in patients with moderate RA. The trial demonstrated significant clinical benefit in the 100 mg mavrilimumab cohort compared to the placebo group.

EXPERT OPINION

The novel molecular targeting mechanism of mavrilimumab together with its demonstrated clinical efficacy, tolerability and safety profile in Phase II clinical trials in moderate RA, suggests significant potential utility for this drug to induce clinical remission, reduce flares and improve morbidity and mortality in patients with RA.

Effects of collagen-induced rheumatoid arthritis on amyloidosis and microvascular pathology in APP/PS1 mice

Background

Evidence suggests that rheumatoid arthritis (RA) may enhance or reduce the progression of Alzheimer's disease (AD). The present study was performed to directly explore the effects of collagen-induced rheumatoid arthritis (CIA) on amyloid plaque formation, microglial activation, and microvascular pathology in the cortex and hippocampus of the double transgenic APP/PS1 mouse model for AD. Wild-type or APP/PS1 mice that received type II collagen (CII) in complete Freund's adjuvant (CFA) at 2 months of age revealed characteristics of RA, such as joint swelling, synovitis, and cartilage and bone degradation 4 months later. Joint pathology was accompanied by sustained induction of IL-1β and TNF-α in plasma over 4 weeks after administration of CII in CFA.

Results

CIA reduced levels of soluble and insoluble amyloid beta (Aβ) peptides and amyloid plaque formation in the cortex and hippocampus of APP/PS1 mice, which correlated with increased blood brain barrier disruption, Iba-1-positive microglia, and CD45-positive microglia/macrophages. In contrast, CIA reduced vessel density and length with features of microvascular pathology, including vascular segments, thinner vessels, and atrophic string vessels.

Conclusions

The present findings suggest that RA may exert beneficial effects against Aβ burden and harmful effects on microvascular pathology in AD.

Mechanistic modeling of antigen sink effect for mavrilimumab following intravenous administration in patients with rheumatoid arthritis

Mavrilimumab is a fully human monoclonal antibody that binds to granulocyte-macrophage colony stimulating factor receptor α (GM-CSFRα) with high affinity and specificity and has potential application in various inflammatory diseases. The objective of this investigation was to develop a mechanistic population model to characterize the pharmacokinetics of mavrilimumab, the GM-CSFRα-mediated clearance, and receptor occupancy following single intravenous dosing to patients with rheumatoid arthritis. The internalization rate of mavrilimumab-GM-CSFRα complex was fixed to a value determined from quantitative confocal fluorescent imaging. The estimated typical first-order clearance and the central and peripheral distribution volumes were 3.79 mL/kg/d, 39.6 mL/kg, and 50.3 mL/kg, respectively. The systemic GM-CSFRα expression level was estimated to be 0.0782 nM, and the equilibrium dissociation constant (0.103 nM) was in good agreement with the monovalent affinity determined by surface plasmon resonance. By fitting to the observed pharmacokinetic data, the mechanistic model predicted that systemically greater than 90% GM-CSFRα blockade by mavrilimumab was achieved and maintained up to 4, 7, and 11 weeks following single 1-, 3-, and 10-mg/kg administrations, respectively. Posterior visual predictive check and bootstrapping suggest that the mechanistic model is reasonably robust and can be used to predict mavrilimumab exposure under various scenarios for future clinical trial design.