Why did IL-23p19 inhibition fail in AS: a tale of tissues, trials or translation?

Predominant ligament-centric soft-tissue involvement differentiates axial psoriatic arthritis from ankylosing spondylitis

Since the original description of spondyloarthritis 50 years ago, results have demonstrated similarities and differences between ankylosing spondylitis (AS) and axial psoriatic arthritis (PsA). HLA-B27 gene carriage in axial inflammation is linked to peri-fibrocartilaginous sacroiliac joint osteitis, as well as to spinal peri-entheseal osteitis, which is often extensive and which provides a crucial anatomical and immunological differentiation between the AS and PsA phenotypes. Specifically, HLA-B27-related diffuse bone marrow oedema (histologically an osteitis) and bone marrow fatty corners detected via magnetic resonance imaging, as well as radiographic changes such as sacroiliitis, vertebral squaring, corner erosions and Romanus lesions, all indicate initial bone phenotypes in HLA-B27+ axial disease. However, in much of PsA with axial involvement, enthesitis primarily manifests in ligamentous soft tissue as 'ligamentitis', with characteristic lesions that include para-syndesmophytes and sacroiliac joint bony sparing. Like axial PsA, diffuse idiopathic skeletal hyperostosis phenotypes, which can be indistinguishable from PsA, exhibit a thoracic and cervical spinal ligamentous soft-tissue tropism, clinically manifesting as syndesmophytosis that is soft-tissue-centric, including paravertebral soft-tissue ossification and sacroiliac soft-ligamentous ossification instead of joint-cavity fusion. The enthesis bone and soft tissues have radically different immune cell and stromal compositions, which probably underpins differential responses to immunomodulatory therapy, especially IL-23 inhibition.

The role of γδ T cells in the immunopathogenesis of inflammatory diseases: from basic biology to therapeutic targeting

The γδ T cells are lymphocytes with an innate-like phenotype that can distribute to different tissues to reside and participate in homeostatic functions such as pathogen defense, tissue modeling, and response to stress. These cells originate during fetal development and migrate to the tissues in a TCR chain-dependent manner. Their unique manner to respond to danger signals facilitates the initiation of cytokine-mediated diseases such as spondyloarthritis and psoriasis, which are immune-mediated diseases with a very strong link with mucosal disturbances, either in the skin or the gut. In spondyloarthritis, γδ T cells are one of the main sources of IL-17 and, therefore, the main drivers of inflammation and probably new bone formation. Remarkably, this population can be the bridge between gut and joint inflammation.

Axial Spondyloarthritis: Evolving concepts regarding the disease's diagnosis and treatment

Spondyloarthritis (SpA) is a chronic inflammatory disease that affects the axial skeleton (axSpA) and/or the peripheral joints (p-SpA) and entheses. The natural history of SpA in the decades of the 80 and 90 s involved a progressive disease with pain, spinal stiffness, ankylosis of the axial skeleton, structural damage of peripheral joints, and a poor prognosis. In the last 20 years, enormous advances in understanding and managing SpA have occurred. With the introduction of the ASAS classification criteria and MRI, early disease recognition is now possible. The ASAS criteria widened the spectrum of SpA to include all the disease phenotypes, such as radiographic (r-axSpA), non-radiographic (nr-axSpA), and p-SpA and extraskeletal manifestations. Nowadays, the treatment of SpA is based on a shared decision between patients and rheumatologists and includes non-pharmacological and pharmacological therapies. Moreover, the discovery of TNFα, IL-17, which play a pivotal role in disease pathophysiology, has revolutionized disease management. Thus, new targeted therapies and many biological agents are now available and used in SpA patients. TNFα inhibitors (TNFi), IL-17, and JAK inhibitors were proven to be efficacious, with an acceptable toxicity profile. Overall, their efficacy and safety are comparable with some differences. Sustained clinical disease remission, low disease activity, improvement of patient's quality of life, and prevention of progression of structural damage, are the results of the above interventions. The concept of SpA has changed in the last 20 years. The disease burden can be ameliorated by early and accurate diagnosis and targeting therapies.

What do we know about co-stimulatory and co-inhibitory immune checkpoint signals in ankylosing spondylitis?

Ankylosing spondylitis is the main entity of a family of inflammatory diseases affecting many musculoskeletal (sacroiliac joints, spine, and peripheral joints) and extra-musculoskeletal sites, termed spondyloarthritis. While it is debated whether disease onset is primarily driven by autoimmune or autoinflammatory processes, what is certain is that both innate and adaptive immune responses orchestrate local and systemic inflammation, which leads to chronic pain and immobility. Immune checkpoint signals are one key player in keeping the immune system in check and in balance, but their role in disease pathogenesis is still rather elusive. Therefore, we ran a MEDLINE search utilizing the PubMed platform for a variety of immune checkpoint signals in regard to ankylosing spondylitis. In this review, we summarize the experimental and genetic data available and evaluate the relevance of immune checkpoint signalling in the pathogenesis of ankylosing spondylitis. Markers such as PD-1 and CTLA-4 have been extensively studied and facilitate the concept of an impaired negative immune regulation in ankylosing spondylitis. Other markers are either neglected completely or insufficiently examined, and the data is conflicting. Still, some of those markers remain interesting targets to decipher the pathogenesis of ankylosing spondylitis and to develop new treatment strategies.

Managing psoriatic arthritis in different clinical scenarios

INTRODUCTION

Psoriatic arthritis (PsA) is a chronic, immune-mediated disease characterized by synovio-entheseal inflammation. It is estimated to affect around 30% of patients with psoriasis and significantly reduces patients' physical function and quality of life. There is a growing number of treatment options for PsA, but due to the heterogeneous clinical features of the disease and prevalence of comorbidities, managing PsA can be challenging.

AREAS COVERED

In this article, we review current understanding of the disease and available pharmacological options. Based on published treatment guidelines, emerging evidence and clinical experience, we provide our expert opinion on treatment strategies, taking into consideration the predominant disease domain and the presence of comorbidities, which can impact treatment decisions and clinical outcomes.

EXPERT OPINION

Biological and targeted synthetic disease-modifying agents are dramatically improving the lives of patients with PsA. Biosimilar TNF inhibitors offer a particularly versatile and cost-effective option, whilst newer biologics and targeted synthetic molecules that can be used to treat most domains of psoriatic disease are an attractive alternative to TNF inhibitors. Despite a lack of consensus on treatment sequencing and tapering, it is important that PsA patients, especially those with comorbidities, are looked after by a multidisciplinary team to optimize their care.

Spondyloarthritis with inflammatory bowel disease: the latest on biologic and targeted therapies

Spondyloarthritis (SpA) encompasses a heterogeneous group of chronic inflammatory diseases that can affect both axial and peripheral joints, tendons and entheses. Among the extra-articular manifestations, inflammatory bowel disease (IBD) is associated with considerable morbidity and effects on quality of life. In everyday clinical practice, treatment of these conditions requires a close collaboration between gastroenterologists and rheumatologists to enable early detection of joint and intestinal manifestations during follow-up and to choose the most effective therapeutic regimen, implementing precision medicine for each patient's subtype of SpA and IBD. The biggest issue in this field is the dearth of drugs that are approved for both diseases, as only TNF inhibitors are currently approved for the treatment of full-spectrum SpA-IBD. Janus tyrosine kinase inhibitors are among the most promising drugs for the treatment of peripheral and axial SpA, as well as for intestinal manifestations. Other therapies such as inhibitors of IL-23 and IL-17, phosphodiesterase 4 inhibitor, α4β7 integrin blockers and faecal microbiota transplantation seem to only be able to control some disease domains, or require further studies. Given the growing interest in the development of novel drugs to treat both conditions, it is important to understand the current state of the art and the unmet needs in the management of SpA-IBD.

Phenotypic heterogeneity in psoriatic arthritis: towards tissue pathology-based therapy

Psoriatic arthritis (PsA) is a heterogeneous disease involving multiple potential tissue domains. Most outcome measures used so far in randomized clinical trials do not sufficiently reflect this domain heterogeneity. The concept that pathogenetic mechanisms might vary across tissues within a single disease, underpinning such phenotype diversity, could explain tissue-distinct levels of response to different therapies. In this Review, we discuss the tissue, cellular and molecular mechanisms that drive clinical heterogeneity in PsA phenotypes, and detail existing tissue-based research, including data generated using sophisticated interrogative technologies with single-cell precision. Finally, we discuss how these elements support the need for tissue-based therapy in PsA in the context of existing and new therapeutic modes of action, and the implications for future PsA trial outcomes and design.

Unmet need in rheumatology: reports from the Advances in Targeted Therapies meeting, 2022

To detail the unmet clinical and scientific needs in the field of rheumatology. After a 2-year hiatus due to the SARS-CoV-2 pandemic, the 22nd annual international Advances in Targeted Therapies meeting brought together more than 100 leading basic scientists and clinical researchers in rheumatology, immunology, epidemiology, molecular biology and other specialties. Breakout sessions were convened with experts in five rheumatological disease-specific groups including: rheumatoid arthritis (RA), psoriatic arthritis, axial spondyloarthritis, systemic lupus erythematosus and connective tissue diseases (CTDs). In each group, experts were asked to identify and prioritise current unmet needs in clinical and translational research, as well as highlight recent progress in meeting formerly identified unmet needs. Clinical trial design innovation was emphasised across all disease states. Within RA, developing therapies and trials for refractory disease patients remained among the most important identified unmet needs and within lupus and spondyloarthritis the need to account for disease endotypes was highlighted. The RA group also identified the need to better understand the natural history of RA, pre-RA states and the need ultimately for precision medicine. In CTD generally, experts focused on the need to better identify molecular, cellular and clinical signals of early and undifferentiated disease in order to identify novel drug targets. There remains a strong need to develop therapies and therapeutic strategies for those with treatment-refractory disease. Increasingly it is clear that we need to better understand the natural history of these diseases, including their 'predisease' states, and identify molecular signatures, including at a tissue level, which can facilitate disease diagnosis and treatment. As these unmet needs in the field of rheumatic diseases have been identified based on consensus of expert clinicians and scientists in the field, this document may serve individual researchers, institutions and industry to help prioritise their scientific activities.

Role of neutrophil interleukin-23 in spondyloarthropathy spectrum disorders

Neutrophilic inflammation is a pervasive characteristic common to spondyloarthropathies and related disorders. This inflammation manifests as Munro's microabscesses of the skin and osteoarticular neutrophilic inflammation in patients with psoriatic arthritis, intestinal crypt abscesses in patients with inflammatory bowel disease, ocular hypopyon in anterior uveitis, and neutrophilic macroscopic and microscopic inflammation in patients with Behçet's disease. Strong MHC class I associations are seen in these diseases, which represent so-called MHC-I-opathies, and these associations indicate an involvement of CD8 T-cell immunopathology that is not yet well understood. In this Personal View, we highlight emerging data suggesting that the T-cell-neutrophil axis involves both a T-cell-mediated and interleukin (IL)-17-mediated (type 17) recruitment and activation of neutrophils, and also a sequestration of activated neutrophils at disease sites that might directly amplify type 17 T-cell responses. This amplification likely involves neutrophilic production of IL-23 and proteases as well as other feedback mechanisms that could be regulated by local microbiota, pathogens, or tissue damage. This crosstalk between innate and adaptive immunity offers a novel explanation for how bacterial and fungal microbes at barrier sites could innately control type 17 T-cell development, with the aim of restoring tissue homoeostasis, and could potentially explain features of clinical disease and treatment response, such as the fast-onset action of the IL-23 pathway blockade in certain patients. This axis could be crucial to understanding non-response to IL-23 inhibitors among patients with ankylosing spondylitis, as the axial skeleton is a site rich in neutrophils and a site of haematopoiesis with myelopoiesis in adults.

Precision medicine: the precision gap in rheumatic disease

For many oncological conditions, the application of timely and patient-tailored targeted therapies, or precision medicine, is a major therapeutic development that has provided considerable clinical benefit. However, despite the application of increasingly sophisticated technologies, alongside advanced bioinformatic and machine-learning algorithms, this success is yet to be replicated for the rheumatic diseases. In rheumatoid arthritis, for example, despite an array of targeted biologic and conventional therapeutics, treatment choice remains largely based on trial and error. The concept of the 'precision gap' for rheumatic disease can help us to identify factors that underpin the slow progress towards the discovery and adoption of precision-medicine approaches for rheumatic disease. In a rheumatic disease such as rheumatoid arthritis, it is possible to identify four themes that have slowed progress, solutions to which should help to close the precision gap. These themes relate to our fundamental understanding of disease pathogenesis, how we determine treatment response, confounders of treatment outcomes and trial design.

Cytokines and cytokine receptors as targets of immune-mediated inflammatory diseases-RA as a role model

Recent advances in our understanding in the immune-mediated inflammatory diseases (IMID) are explored and promoted by the targeted treatment. Among these targets, cytokines and cytokine receptors have become the good candidates for the drug development. In this review, the cytokine and cytokine receptors, which are approved in IMID, are overviewed, and modalities of the treatment, the role of cytokines and cytokine receptors in each disease, and the updated molecular information by modern technologies in rheumatoid arthritis as a role model are shown and discussed for the future perspectives.

Levels of Peripheral Th17 Cells and Th17-Related Cytokines in Patients with Ankylosing Spondylitis: A Meta-analysis

BACKGROUND

Ankylosing spondylitis (AS) is a chronic inflammatory disease. Several proinflammatory cytokines produced by T helper 17 (Th17) cells are involved in the pathogenesis of AS. We performed a meta-analysis to determine the levels of Th17 cells and serum Th17-associated cytokines in patients with AS.

METHODS

We determined the levels of Th17 cells and Th17 cytokines in patients with AS using data extracted from published articles retrieved from the PubMed, Embase, Web of Science, Cochrane Library, MEDLINE, Web of Knowledge, Clinical Trials.gov, and FDA.gov.

DATABASES

The effect estimates were pooled using a random-effects model. The review protocols were registered on PROSPERO (reference: CRD42021255741) and followed the PRISMA guideline.

RESULTS

This meta-analysis included 138 studies. Compared to healthy controls (HCs), patients with AS had a higher proportion of Th17 cells (standardized mean difference [SMD] 2.23, 95% confidence interval [CI] 1.78-2.68; p < 0.001) and levels of proinflammatory cytokines, such as interleukin (IL)-17 (SMD 2.04, 95% CI 1.70-2.38; p < 0.001), IL-21 (SMD 1.77, 95% CI 0.95-2.59; p < 0.001), and IL-23 (SMD 1.11, 95% CI 0.78-1.44; p < 0.001). The subgroup analysis showed higher levels of IL-17⁺ Th17 cells among peripheral blood mononuclear cells (PBMCs) and CD4⁺ T cells in patients with AS compared to HCs (SMD 2.26, 95% CI 1.58-2.94 [p < 0.001] and SMD 1.61, 95% CI 0.55-2.67 [p = 0.003], respectively). Patients with AS had higher levels of CD4⁺IL-17⁺IFN-γ^- Th17 in PBMCs and of CD4⁺CCR6⁺CCR4⁺Th17 in CD4⁺ T cells compared to HCs (SMD 1.85, 95% CI 1.06-2.64 [p < 0.001] and SMD 7.72, 95% CI 6.55-8.89 [p < 0.001], respectively). No significant differences were observed in the proportions of CD4⁺IL-17⁺IFN-γ^- Th17 in CD4⁺ T cells and CD4⁺CCR6⁺CCR4⁺ Th17 in PBMCs (SMD - 0.11, 95% CI - 0.61 to 0.38 [p = 0.650] and SMD 1.32, 95% CI - 0.54 to 3.19 [p = 0.165], respectively). In addition, compared to stable AS, the levels of Th17 cells and IL-17 and IL-23 were significantly higher in active AS (SMD 1.58, 95% CI 0.30-2.85 [p = 0.016], SMD 3.52, 95% CI 0.72-6.33 [p = 0.014], and SMD 5.10, 95% CI 1.83-8.36 [p = 0.002], respectively).

CONCLUSIONS

The levels of Th17 cells and serum IL-17, IL-21, and IL-23 were higher in patients with AS than in HCs and, compared with stable AS, they increased more significantly in active AS. These results suggest that Th17 cells and Th17-related cytokines play major roles in AS pathogenesis and are an important target for treatment.

Efficacy and safety of guselkumab in biologic-naïve patients with active axial psoriatic arthritis: study protocol for STAR, a phase 4, randomized, double-blinded, placebo-controlled trial

Background

Axial involvement constitutes a specific domain of psoriatic arthritis (PsA). Interleukin (IL)-23 inhibitors have demonstrated improvement in axial PsA (axPsA) symptoms, but have not shown efficacy in treating ankylosing spondylitis (AS), suggesting differences in axPsA processes and treatments. In a post hoc, pooled analysis of patients with investigator- and imaging-confirmed sacroiliitis in two phase 3, randomized, placebo-controlled studies (DISCOVER-1 and DISCOVER-2), patients treated with guselkumab, an IL-23p19 inhibitor, had greater axial symptom improvements compared with placebo. Confirmatory imaging at baseline was restricted to the sacroiliac (SI) joints, occurred prior to/at screening, and was locally read.

Methods

The STAR study will prospectively assess efficacy outcomes in PsA patients with magnetic resonance imaging (MRI)-confirmed axial inflammation. Eligible, biologic-naïve patients with PsA (N =  405) for ≥ 6 months and active disease (≥ 3 swollen and ≥ 3 tender joints, C-reactive protein [CRP] ≥ 0.3 mg/dL) despite prior non-biologic disease-modifying antirheumatic drugs, apremilast, and/or nonsteroidal anti-inflammatory drugs will be randomized (1:1:1) to guselkumab every 4 weeks (Q4W); guselkumab at week (W) 0, W4, then every 8 weeks (Q8W); or placebo with crossover to guselkumab at W24, W28, then Q8W. Patients will have Bath Ankylosing Spondylitis Disease Activity Index (BASDAI) score ≥ 4, spinal pain component score (0–10 visual analog scale) ≥ 4, and screening MRI-confirmed axial involvement (positive spine and/or SI joints according to centrally read Spondyloarthritis Research Consortium of Canada [SPARCC] score ≥ 3 in ≥ 1 region). The primary endpoint is mean change from baseline in BASDAI at W24; multiplicity controlled secondary endpoints at W24 include AS Disease Activity Score employing CRP (ASDAS), Disease Activity Index for PsA (DAPSA), Health Assessment Questionnaire – Disability Index (HAQ-DI), Investigator’s Global Assessment of skin disease (IGA), and mean changes from baseline in MRI SI joint SPARCC scores. Centrally read MRIs of spine and SI joints (scored using SPARCC) will be obtained at W0, W24, and W52, with readers blinded to treatment group and timepoint. Treatment group comparisons will be performed using a Cochran-Mantel-Haenszel or chi-square test for binary endpoints and analysis of covariance, mixed model for repeated measures, or constrained longitudinal data analysis for continuous endpoints.

Discussion

This study will evaluate the ability of guselkumab to reduce both axial symptoms and inflammation in patients with active PsA.

Trial registration

This trial was registered at ClinicalTrials.gov, NCT04929210, on 18 June 2021.

Protocol version: Version 1.0 dated 14 April 2021.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13063-022-06589-y.

Inhibiting IL-17A and IL-17F in Rheumatic Disease: Therapeutics Help to Elucidate Disease Mechanisms

Purpose of Review

Psoriatic arthritis and ankylosing spondylitis belong to a family of rheumatological diseases that lead to painful joint inflammation that impacts on patient function and quality of life. Recent studies have shown that the pro-inflammatory cytokine IL-17 is involved in the inflammatory joint changes in spondyloarthritides. We will review the pathophysiology of IL-17 and review the biological therapies targeting IL-17.

Recent Findings

IL-17 is produced and released from T cells and is dependent on multiple upstream cytokines, which include IL-23. There are six members of the IL-17 family that are secreted from multiple populations of T cells. The initial biologic medications have been developed against IL-17A, which is the best-studied member of this family. These medications appear to be effective in controlling joint inflammation, improving patient quality of life, and are generally well tolerated. More recently, medications have been developed that target both IL-17A and IL-17F. In addition, brodalumab, an antibody targeting the IL-17 receptor, has had a resurgence after initial concerns for an increased risk of suicide.

Summary

IL-17 is an inflammatory cytokine that is critical in the pathobiology of axial spondyloarthritides. Recent biological therapies targeting IL-17A are effective and well tolerated in patients with axial spondyloarthritis. Specific targeting of the Il-17A/F heterodimer is also effective and provides another viable option in the clinician’s armamentarium.

Treatment of axial spondyloarthritis: an update

Diagnosis and management of axial spondyloarthritis (axSpA) has vastly improved over the past two decades. With advances in the discernment of immunopathogenesis of this disease, new therapies have become available, which are associated with substantial improvement in symptoms, signs and quality of life. The four broad categories of approved treatment options are physical therapy and exercise (which have been known to be beneficial for millennia), NSAIDs (since the 1950s), TNF inhibitors (first FDA approval in 2003) and IL-17 inhibitors (first FDA approval in 2016). In addition, there have been a host of new developments in the axSpA field, including new treatment guidelines, the FDA approval of three biologic DMARDs to treat non-radiographic axSpA, the FDA and EMA approval of Janus kinase (JAK) inhibitors for ankylosing spondylitis, new data on the effect of biologic DMARDs on structural progression in ankylosing spondylitis, strategy trials on tapering or stopping TNF inhibitors in patients in remission, trials of treat-to-target strategy in axSpA, and several new molecules in phase III studies. This Review explores the developments in the management of axSpA.

Upregulation of Unfolded Protein Response and ER Stress-Related IL-23 Production in M1 Macrophages from Ankylosing Spondylitis Patients

The inflammatory interleukin (IL)-23/IL-17 axis plays an important role in the pathogenesis of ankylosing spondylitis (AS), but with an unknown regulatory mechanism. This study aimed to investigate the role of endoplasmic reticulum (ER) stress and autophagy pathway in the expression of IL-23 in peripheral blood-derived macrophages in AS patients. Peripheral blood samples were obtained from 15 AS and 15 healthy control subjects. MACS was used to isolate monocytes from PBMCs. Then, M-CSF was used to differentiate monocytes to M2 macrophages. IFN-γ and/or LPS were used to activate macrophages and M2 polarization towards M1 macrophages. Thapsigargin was used to induce ER stress and 3-MA to inhibit autophagy. The purity of extracted monocytes and macrophage markers was evaluated by flow cytometry. mRNA expression of HLA-B and-B27, ER stress-related genes, autophagy-related genes, and IL-23p19 was performed using RT-qPCR. Soluble levels of IL-23p19 were measured using ELISA. Significant increase in mRNA expression of HLA-B, HLA-B27, BiP, XBP1, CHOP, and PERK mRNAs was observed in macrophages of AS patients before and after stimulation with IFN-γ and LPS. No significant change in autophagy gene expression was detected. mRNA and soluble levels of IL-23p19 demonstrated a significant increase in macrophages of AS patients compared to healthy subjects. ER stress induction led to a significant increase in IL-23p19 in macrophages. Inhibition of autophagy did not affect IL-23 expression. ER stress, unlike autophagy, is associated with increased IL-23 levels in macrophages of AS patients.Key Messages ER stress in macrophages from AS patients plays a role in the increased production of IL-23. The autophagy pathway is not involved in the modulation of IL-23 production by AS macrophages.

Comprehensive Review Exploring Novel Treatments for Psoriatic Arthritis and Axial Spondyloarthritis from 2016 to 2021

Over the past decade, numerous novel therapies have been approved for use in the seronegative spondyloarthritides, including psoriatic arthritis and axial spondyloarthritis. With large variability seen in the spondyloarthritides with respect to presentation and perhaps pathogenesis, potential therapies continue to be discovered and trialled in the hope of better controlling disease activity. This review details therapies that have emerged for the treatment of psoriatic arthritis and axial spondyloarthritis from 2016 to 2021. We discuss those that have been approved for use in the USA and those that remain under investigation.

The gut-enthesis axis and the pathogenesis of Spondyloarthritis

Subclinical inflammation is associated with Spondylarthritis (SpA). SpA patients show features of dysbiosis, altered gut barrier function, and local expansion of innate and innate-like cells involved in type 3 immune response. The recirculation of intestinal primed immune cells into the bloodstream and, in some cases, in the joints and the inflamed bone marrow of SpA patients gave the basis of the gut-joint axis theory. In the light of the critical role of enthesis in the pathogenesis of SpA and the identification of mucosal-derived immune cells residing into the normal human enthesis, a gut-enthesis axis is also likely to exist. This work reviews the current knowledge on enthesis-associated innate immune cells' primary involvement in enthesitis development, questions their origin, and critically discusses the clues supporting the existence of a gut-enthesis axis contributing to SpA development.

IL-23 and axial disease: do they come together?

IL-23 is a key cytokine in the pathogenesis of spondyloarthritides, including PsA and axial spondyloarthritis, as well as related conditions, such as psoriasis and IBD. Genetic associations, animal models and translational studies in humans demonstrate the key role played by IL-23, especially when coupled with downstream overexpression of IL-17 via stimulation of T helper 17 (Th17) and other cells by IL-23. Whereas IL-23 inhibition has shown clear-cut benefit in psoriasis and peripheral manifestations of PsA, trials of IL-23 inhibitors have failed in the treatment of ankylosing spondylitis. More recently, exploratory data from PsA patients with axial symptoms suggests that improvement may occur, but needs confirmation in dedicated axial spondyloarthritis (axSpA) trials. Hypotheses for these apparently conflicting findings about IL-23 inhibition in various forms of spondylitis are discussed.

Recent Updates in Juvenile Spondyloarthritis

Spondyloarthritis represents a group of disorders characterized by enthesitis and axial skeletal involvement. Juvenile spondyloarthritis begins before age 16. Joint involvement is usually asymmetric. Bone marrow edema on noncontrast MRI of the sacroiliac joints can facilitate diagnosis. The most significant risk factor for axial disease is HLA-B27. Most patients have active disease into adulthood. Enthesitis and sacroiliitis correlate with greater pain intensity and poor quality-of-life measures. Tumor necrosis factor inhibitors are the mainstay of biologic therapy. Although other biologics such as IL-17 blockers have shown benefit in adult spondyloarthritis, none are approved by the US Food and Drug Administration.

Inflammatory Foot Involvement in Spondyloarthritis: From Tarsitis to Ankylosing Tarsitis

Spondyloarthritis (SpA) is a group that includes a wide spectrum of clinically similar diseases manifested by oligoarticular arthritis and axial or peripheral ankylosis. Although axial SpA is predominant in Caucasians and adult-onset patients, juvenile-onset and Latin American patients are characterized by severe peripheral arthritis and particularly foot involvement. The peripheral involvement of SpA can vary from tarsal arthritis to the most severe form named ankylosing tarsitis (AT). Although the cause and etiopathogenesis of axSpA are often studied, the specific characteristics of pSpA are unknown. Several animal models of SpA develop initial tarsitis and foot ankylosis as the main signs, emphasizing the role of foot inflammation in the overall SpA spectrum. In this review, we attempt to highlight the clinical characteristics of foot involvement in SpA and update the knowledge regarding its pathogenesis, focusing on animal models and the role of mechanical forces in inflammation.

Immune-mediated inflammatory disease therapeutics: past, present and future

Immune-mediated inflammatory diseases are common and clinically diverse. Although they are currently incurable, the therapeutic armamentarium for immune-mediated inflammatory diseases has been transformed in the past two decades. We have moved from the wide application of broad-spectrum immune modulators to the routine use of agents with exquisite specificity, arising from monoclonal and molecular biotechnology and more recently from highly targeted medicinal chemistry. Here we describe key advances and lessons that drove this remarkable progress and thereafter reflect on the next steps in this ongoing journey.

Differentiating Psoriatic Arthritis from Osteoarthritis and Rheumatoid Arthritis: A Narrative Review and Guide for Advanced Practice Providers

Psoriatic arthritis (PsA) is a chronic inflammatory disease that affects multiple organ systems and is characterized by skin and joint manifestations. PsA is frequently undiagnosed and/or misdiagnosed, especially because of the similarities in clinical presentation shared with other arthritic diseases, including rheumatoid arthritis (RA) and osteoarthritis (OA). An accurate and timely diagnosis of PsA is crucial to prevent delays in optimal treatment, which can lead to irreversible joint damage and increased functional disability. Patients are usually seen by a number of different healthcare providers on their path to a diagnosis of PsA, including advanced practice providers (APPs). This review provides a comprehensive overview of the characteristic features that can be used to facilitate the differentiation of PsA from RA and OA. Detailed information on clinical manifestations, biomarkers, radiologic features, and therapeutic recommendations for PsA included here can be applied in routine clinical settings to provide APPs with the confidence and knowledge to recognize and refer patients more accurately to rheumatologists for management of patients with PsA.

Guselkumab induces robust reduction in acute phase proteins and type 17 effector cytokines in active psoriatic arthritis: results from phase 3 trials

OBJECTIVE

To investigate serum protein expression in participants with psoriatic arthritis (PsA) and changes after guselkumab treatment.

METHODS

Participants with PsA were treated with guselkumab or placebo in the DISCOVER-1 and DISCOVER-2 studies. Serum levels of acute phase reactants C reactive protein (CRP) and serum amyloid A (SAA) and inflammatory cytokines/chemokines were measured at weeks 0, 4 and 24 in 300 study participants and 34 healthy controls (HCs). The PSUMMIT studies measured serum interleukin (IL)-17A, IL-17F and CRP after ustekinumab treatment and levels with ustekinumab versus guselkumab treatment were compared.

RESULTS

Baseline serum levels of CRP, SAA, IL-6, IL-17A and IL-17F were elevated in participants with active PsA vs HCs (p<0.05, geometric mean (GM) ≥40% higher). Baseline T-helper cell 17 (Th17) effector cytokines were significantly associated with baseline psoriasis but not joint disease activity. Compared with placebo, guselkumab treatment resulted in decreases in serum CRP, SAA, IL-6, IL-17A, IL-17F and IL-22 as early as week 4 and continued to decrease through week 24 (p<0.05, GM decrease from baseline ≥33%). At week 24, IL-17A and IL-17F levels were not significantly different from HCs, suggesting normalisation of peripheral IL-23/Th17 axis effector cytokines postguselkumab treatment. Reductions in IL-17A/IL-17F levels were greater in guselkumab-treated versus ustekinumab-treated participants, whereas effects on CRP levels were similar.

CONCLUSION

Guselkumab treatment reduced serum protein levels of acute phase and Th17 effector cytokines and achieved comparable levels to those in HCs. In participants with PsA, reductions of IL-17A and IL-17F were of greater magnitude after treatment with guselkumab than with ustekinumab.

Systematic Review and Meta-Analysis of Inflammatory Bowel Disease Adverse Events with Anti-Interleukin 17A Agents and Tumor Necrosis Factor Inhibitors in Rheumatic Disease and Skin Psoriasis

Introduction

The aim of this work is to perform a systematic review and meta-analysis of anti-tumor necrosis factor (anti-TNF) and anti-interleukin-17 (anti-IL-17) trials for spondyloarthritis, psoriatic arthritis, and psoriasis comparing rates of inflammatory bowel disease (IBD) events compared to placebo.

Methods

MEDLINE, EMBASE, and The Cochrane Library were searched for double-blind, randomized placebo-controlled anti-TNF and anti-IL-17 trials of included diseases. Inflammatory bowel disease events from the RCT period were pooled and meta-analyzed using statistical methods suitable for low-event-rate meta-analysis (Peto’s, Mantel–Haenszel, hypergeometric-normal model, and Shuster-Guo-Skyler). When observed data were insufficient, we performed an exploratory sensitivity analysis to compare methods.

Results

We identified 9551 original papers, and included 96 publications: 65 anti-TNF and 31 anti-IL-17 trials, containing 21 new and 12 flare IBD events in 28,209 participants. New IBD on anti-IL-17 occurred 0.23/100 patient-years (PY) in psoriasis, 0.61/100 PY in PsA and 1.63/100 PY in spondyloarthritis, rates similar to observational cohorts, and less commonly on anti-TNF (0/100 PY, 0/100 PY, 0.32/100 PY, respectively). No evidence of difference between groups was found, with wide CI from many pooled counts of zero, especially in placebo arms.

Conclusions

IBD events were rare, occurring at rates similar to biologic-naive groups. We could not find statistically significant differences in risk of new or recurrent IBD between treatment and control groups using selected meta-analytical methods for low event rate scenarios. Meta-analyses of this topic require more IBD events, ideally without pooling heterogeneous groups. Larger, thoroughly reported trials with systematic and detailed safety reporting are required to improve risk estimation and to make accurate inferences.

Supplementary Information

The online version contains supplementary material available at 10.1007/s40744-021-00360-6.

IL-23 inhibition for the treatment of psoriatic arthritis

Introduction: Psoriatic arthritis (PsA) is a complex, polygenic immune-mediated disease with varying clinical presentations involving the skin, nails, entheses, and axial/peripheral skeleton.Areas covered: Pathophysiology of PsA with special focus on IL-23/IL-17 axis. Novel classes of targeted therapies for PsA. Pharmacologic properties, efficacy and safety of guselkumab, the only FDA approved agent from IL-23p19 inhibitor class. Data regarding other IL-23 inhibitors (Ustekinumab - an IL-12/IL-23p40 inhibitor, Risankizumab and Tildrakizumab - both IL23p19 inhibitors), in the treatment of PsA.Expert opinion: There are seven classes of FDA-approved therapies for the treatment of PsA. IL-23p19 inhibitors are the newest class of medications that has shown efficacy and reasonable safety profile in the treatment of PsA in phase 2 and phase 3 studies; Guselkumab is the only FDA-approved biologic for PsA within this class . While no head-to-head studies of IL-23p19 inhibitors and other PsA targeted therapies are available, the efficacy of these agents on musculoskeletal system appears to be comparable to TNF-inhibitors (TNFi), and the efficacy on the skin appears to be comparable, or modestly superior to the IL-17 inhibitors (IL-17i). With a superior safety profile compared to TNFi and IL-17i, IL-23p19 inhibitors have the potential to become a first-line biologic in the treatment of PsA.

Peripheral Enthesitis in Spondyloarthritis: Lessons from Targeted Treatments

A significant proportion of patients with spondyloarthritis (SpA) have peripheral enthesitis. Data suggest that psoriatic arthritis (PsA) patients with enthesitis have a higher disease burden than those without enthesitis. Over the past decade, there has been a proliferation of treatment options for spondyloarthropathy. These medications target multiple signaling pathways, including tumor necrosis factor (TNF), interleukin (IL)-17A, IL-12/23, IL-23, thymus (T)-cell co-stimulation, intracellular Janus kinases, and phosphodiesterase enzymes. As a key domain in SpA, enthesitis outcomes are included in pivotal trials of these agents and are reported as secondary outcome measures. One significant limitation is that the clinical evaluation of enthesitis relies on eliciting tenderness on palpation and is insensitive when compared with imaging. Furthermore, direct comparisons between studies are not available due to the use of different outcome measures, lack of consistent and comprehensive reporting outcomes, and subgroup analyses with a lower number of patients with enthesitis. This systematic review describes the epidemiology, pathophysiology, and available targeted therapies against enthesitis, as well as a detailed report of their efficacy. One major trend identified during this review is incomplete reporting of outcome measures, as many studies reported proportions of enthesitis prevalence. Factors that affected responsiveness in clinical trials included the entheseal instrument used, the number of subjects available for comparison, as well as the therapeutic agent. In general, anti-TNF and anti-IL-17 agents, as well as Janus kinase inhibitors, show moderate responsiveness for enthesitis. The data for IL-23 targeting is contradictory.

From Science to Success? Targeting Tyrosine Kinase 2 in Spondyloarthritis and Related Chronic Inflammatory Diseases

Spondyloarthritis (SpA) is a family of inflammatory arthritic diseases, which includes the prototypes of psoriatic arthritis and ankylosing spondylitis. SpA is commonly associated with systemic inflammatory diseases, such as psoriasis and inflammatory bowel disease. Immunological studies, murine models and the genetics of SpA all indicate a pathogenic role for the IL-23/IL-17 axis. Therapeutics targeting the IL-23/IL-17 pathway are successful at providing symptomatic relief, but may not provide complete protection against progression of arthritis. Thus there is still tremendous interest in the discovery of novel therapeutic targets for SpA. Tyrosine kinase 2 (TYK2) is a member of the Janus kinases, which mediate intracellular signaling of cytokines via signal transducer and activator of transcription (STAT) activation. TYK2 plays a crucial role in mediating IL-23 receptor signaling and STAT3 activation. A plethora of natural mutations in and around TYK2 have provided a wealth of data to associate this kinase with autoimmune/autoinflammatory diseases in humans. Induced and natural mutations in murine Tyk2 largely support human data; however, key inter-species differences exist, which means extrapolation of data from murine models to humans needs to be done with caution. Despite these reservations, novel selective TYK2 inhibitors are now proving successful in advanced clinical trials of inflammatory diseases. In this review, we will discuss TYK2 from basic biology to therapeutic targeting, with an emphasis on studies in SpA. Seminal studies uncovering the basic science of TYK2 have provided sound foundations for targeting it in SpA and related inflammatory diseases. TYK2 inhibitors may well be the next blockbuster therapeutic for SpA.

Secukinumab for the treatment of psoriasis, psoriatic arthritis, and axial spondyloarthritis: Physical and pharmacological properties underlie the observed clinical efficacy and safety

Psoriasis, psoriatic arthritis, and axial spondyloarthritis are systemic inflammatory diseases, each commonly manifesting as a spectrum of symptoms, complications, and comorbidities that arise differently in individual patients. Drugs targeting inflammatory cytokines common to the pathogenesis of each of these conditions have been developed, although their specific actions in the different tissues involved are variable. For a drug to be effective, it must be efficiently delivered to and locally bioactive in disease-relevant tissues. Detailed clinical data shed light on the therapeutic effects of individual biologics on specific domains or clinical manifestations of disease and assist in guiding treatment decisions. Pharmacologic, molecular, and functional properties of drugs strongly impact their observed safety and efficacy, and an understanding of these properties provides complementary insight. Secukinumab, a fully human monoclonal IgG1/κ antibody selectively targeting interleukin (IL)-17A, has been in clinical use for >6 years in the treatment of moderate to severe psoriasis, psoriatic arthritis, and both radiographic (also known as ankylosing spondylitis) and nonradiographic axial spondyloarthritis. In this review, we discuss pharmacokinetic and pharmacodynamic data for secukinumab to introduce clinicians to the pharmacological properties of this widely used drug. Understanding how these properties affect the observed clinical efficacy, safety, and tolerability of this drug in the treatment of IL-17A-mediated systemic inflammatory diseases is important for all physicians treating these conditions.

Biomarkers predictive of treatment response in psoriasis and psoriatic arthritis: a systematic review

AIMS

The ability to predict response to treatment remains a key unmet need in psoriatic disease. We conducted a systematic review of studies relating to biomarkers associated with response to treatment in either psoriasis vulgaris (PsV) or psoriatic arthritis (PsA).

METHODS

A search was conducted in PubMed, Embase and the Cochrane library from their inception to 2 September 2020, and conference proceedings from four major rheumatology conferences. Original research articles studying pre-treatment biomarker levels associated with subsequent response to pharmacologic treatment in either PsV or PsA were included.

RESULTS

A total of 765 articles were retrieved and after review, 44 articles (22 relating to PsV and 22 to PsA) met the systematic review's eligibility criteria. One study examined the response to methotrexate, one the response to tofacitinib and all the other studies to biologic disease-modifying antirheumatic drugs (DMARDs). Whilst several studies examined the HLA-C*06 allele in PsV, the results were conflicting. Interleukin (IL)-12 serum levels and polymorphisms in the IL-12B gene show promise as biomarkers of treatment response in PsV. Most, but not all, studies found that higher baseline levels of C-reactive protein (CRP) were associated with a better clinical response to treatment in patients with PsA.

CONCLUSION

Several studies have identified biomarkers associated with subsequent response to treatment in psoriatic disease. However, due to the different types of biomarkers, treatments and outcome measures used, firm conclusions cannot be drawn. Further validation is needed before any of these biomarkers translate to clinical practice.

Crossing the boundaries: IL-23 and its role in linking inflammation of the skin, gut and joints

Several lines of evidence point towards the central role of IL-23 as a crucial inflammatory mediator in the pathogenesis of SpA—a group of inflammatory arthritic diseases whose symptoms span the skin, gastrointestinal tract and joints. While therapeutic blockade of IL-23 proved successful in the treatment of IBD, psoriatic skin disease and peripheral SpA, it failed in patients suffering from SpA with predominantly axial involvement. Here we review state-of-the-art discoveries on IL-23 signalling pathways across target tissues involved in SpA. We discuss the discrepancies in resident IL-23–responding cells and their downstream activities across skin, gut and joint that shape the unique immunological landscape of SpA.

Drivers of Inflammation in Psoriatic Arthritis: the Old and the New

PURPOSE OF REVIEW

The recognition that IL-17 is produced by many lymphoid-like cells other than CD4+ T helper (Th17) cells raises the potential for new pathogenic pathways in IBD/psoriasis/SpA. We review recent knowledge concerning the role of unconventional and conventional lymphocytes expressing IL-17 in human PsA and axSpA.

RECENT FINDINGS

Innate-like lymphoid cells, namely gamma delta (γδ) T-cells, invariant natural killer T (iNKT) cells and mucosal-associated invariant T (MAIT) cells, together with innate lymphoid cells (ILCs) are found at sites of disease in PsA/SpA. These cells are often skewed to Type-17 profiles and may significantly contribute to IL-17 production. Non-IL-23 dependent IL-17 production pathways, utilising cytokines such as IL-7 and IL-9, also characterise these cells. Both conventional CD4 and CD8 lymphocytes show pathogenic phenotypes at sites of disease. A variety of innate-like lymphoid cells and conventional lymphocytes contribute towards IL-17-mediated pathology in PsA/SpA. The responses of these cells to non-conventional immune and non-immune stimuli may explain characteristic clinical features of these diseases and potential therapeutic mechanisms of therapies such as Jak inhibitors.

The IL-23/IL-17A axis in spondyloarthritis: therapeutics informing pathogenesis?

PURPOSE OF REVIEW

To give an overview of the recently published trials relating to IL-23/IL-17 pathway in spondyloarthritis (SpA).

RECENT FINDINGS

Recent studies in psoriasis confirmed the efficacy of targeting the IL-23/IL-17 pathway, with emerging evidence from head-to-head studies suggesting functional hierarchy of these inhibitors. In psoriatic arthritis (PsA), recent studies have indicated the efficacy of inhibiting IL-23p19, in addition to IL-23p40 and IL-17A, albeit all with lower hurdle results than those seen in psoriasis. The first head-to-head study of an IL-17A and tumour necrosis factor inhibitor in PsA has also recently been published. Recent studies have demonstrated the efficacy of the IL-17A inhibitor, ixekizumab, across the axial SpA spectrum. In contrast, inhibition of IL-12/IL-23p40 and IL-23p19 both failed in axial SpA. In inflammatory bowel disease (IBD), recent studies indicate efficacy of IL-23p40 and IL-23p19 inhibition, in contrast to the previous failed studies of IL-17 inhibition.

SUMMARY

Clinical trials of IL-23/IL-17 inhibition have been transformative in psoriasis, with more mixed results in PsA and differential responses in axial SpA and IBD. These results pose challenges to our fundamental understanding of SpA pathogenesis and further head-to-head studies and more subtle evaluation of the local tissue-specific aspects will be required.

Predictors of extra-articular manifestations in axial spondyloarthritis and their influence on TNF-inhibitor prescribing patterns: results from the British Society for Rheumatology Biologics Register in Ankylosing Spondylitis

OBJECTIVES

Extra-articular manifestations (EAMs) are important systemic features of axial spondyloarthritis (axSpA), which may influence the choice of tumour necrosis factor-inhibitor (TNFi). We examined the cumulative incidence and predictors of EAMs and the influence of these on first TNFi choice in a 'real-world' cohort of patients with axSpA.

METHODS

Clinical and patient-reported outcomes of 2420 patients with axSpA from 83 centres were collected by the British Society for Rheumatology Biologics Register in Ankylosing Spondylitis. Lifestyle factors for EAMs (acute anterior uveitis (AAU), inflammatory bowel diseases (IBD), psoriasis) were compared with those without EAMs. Also, the association between pretreatment EAMs and choice of first TNFi (adalimumab, etanercept, certolizumab) was analysed.

RESULTS

AAU was directly associated with human leukocyte antigen (HLA)-B27 (incidence rate ratio (IRR) 1.95, 95% CI 1.40 to 2.73) and inversely associated with ever-smoking (IRR=0.71, 95% CI 0.55 to 0.92). For both psoriasis and IBD, there was an inverse relationship with HLA-B27 (IRR 0.54, 95% CI 0.36 to 0.79 and IRR 0.63, 95% CI 0.43 to 0.91, respectively). A diagnosis of either AAU (OR 3.79, 95% CI 2.11 to 6.80) or IBD (OR 5.50, 95% CI 2.09 to 14.46) was associated with preference for adalimumab versus others. In contrast, a diagnosis of either AAU (OR 0.14, 95% CI 0.06 to 0.33) or IBD (OR 0.17, 95% CI 0.05 to 0.57) was associated with less preference for etanercept over other TNFi.

CONCLUSION

The higher occurrence of AAU and lower occurrence of psoriasis and IBD in HLA-B27-positive patients with axSpA are consistent with current pathophysiology. Patients with previous AAU and IBD are more likely to be prescribed adalimumab and less likely to receive etanercept, consistent with the superior efficacy of monoclonal TNFi for these indications. Future work will determine whether EAMs influence TNFi survival, or effectiveness, and whether this varies between agents.

Effects of ustekinumab on spondylitis-associated endpoints in TNFi-naïve active psoriatic arthritis patients with physician-reported spondylitis: pooled results from two phase 3, randomised, controlled trials

BACKGROUND

The interleukin-12/23p40-subunit-inhibitor ustekinumab significantly improved spondylitis-related symptoms through Week 24 in psoriatic arthritis (PsA) patients with peripheral arthritis and physician-reported spondylitis (PA-PRS) in PSUMMIT-1&2. We further evaluated ustekinumab's effect on spondylitis-related endpoints in PSUMMIT-1&2 tumour necrosis factor-inhibitor (TNFi)-naïve patients with PA-PRS.

METHODS

Patients with active PsA (≥5 swollen and ≥5 tender joints, C-reactive-protein ≥ 3.0 mg/L) despite conventional (PSUMMIT-1&2) and/or prior TNFi (PSUMMIT-2) therapy received subcutaneous ustekinumab 45 mg, 90 mg or placebo (Week 0, Week 4, Week 16). Changes in Bath Ankylosing Spondylitis Disease Activity Index (BASDAI) neck/back/hip pain question (#2) and modified BASDAI (mBASDAI, excluding PA) scores and Ankylosing Spondylitis Disease Activity Score (ASDAS) responses were assessed at Weeks 12 and 24.

RESULTS

The pooled PSUMMIT-1&2, TNFi-naïve (n=747), PA-PRS (n=223) subset (158 with human-leucocyte-antigen (HLA)-B27 results) presented with moderate-to-severe spondylitis-related symptoms (mean BASDAI-neck/back/hip pain-6.51, mBASDAI-6.54, BASDAI-6.51, ASDAS-3.81). Mean Week 24 changes were larger among ustekinumab than placebo-treated patients for both neck/back/hip pain (-1.99 vs -0.18) and mBASDAI (-2.09 vs -0.59). Improvements in neck/back/hip pain and fatigue appeared numerically greater in HLA-B27⁺ than HLA-B27 ^- patients; those for other domains were generally consistent. Greater proportions of ustekinumab versus placebo-treated patients achieved ASDAS clinically important improvement at Week 24 (decrease ≥ 1.1; 49.6% vs 12.7%; nominal p<0.05).

CONCLUSIONS

Improvements in BASDAI neck/back/hip pain and mBASDAI among ustekinumab-treated, TNFi-naïve, PsA patients with PA-PRS were clinically meaningful and consistent across assessment tools. Numerically greater improvements in neck/back/hip pain in HLA-B27⁺ than HLA-B27 ^- patients, noted in the context of similar overall mBASDAI improvements between the subgroups, suggest ustekinumab may improve disease activity in TNFi-naïve PsA patients likely to exhibit axial disease.

CLINICAL TRIAL REGISTRATION NUMBERS

PSUMMIT 1, NCT01009086; PSUMMIT 2, NCT01077362.

Why Inhibition of IL-23 Lacked Efficacy in Ankylosing Spondylitis

The term spondyloarthritis pertains to both axial and peripheral arthritis including ankylosing spondylitis (AS) and psoriatic arthritis (PsA), which is strongly linked to psoriasis and also the arthritis associated with inflammatory bowel disease. The argument supporting the role for IL-23 across the spectrum of SpA comes from 4 sources. First, genome wide associated studies (GWAS) have shown that all the aforementioned disorders exhibit IL-23R pathway SNPs, whereas HLA-B27 is not linked to all of these diseases-hence the IL-23 pathway represents the common genetic denominator. Secondly, experimental animal models have demonstrated a pivotal role for the IL-23/IL-17 axis in SpA related arthropathy that initially manifests as enthesitis, but also synovitis and axial inflammation and also associated aortic root and cutaneous inflammation. Thirdly, the emergent immunology of the human enthesis also supports the presence of IL-23 producing myeloid cells, not just at the enthesis but in other SpA associated sites including skin and gut. Finally, drugs that target the IL-23 pathway show excellent efficacy for skin disease, efficacy for IBD and also in peripheral arthropathy associated with SpA. The apparent failure of IL-23 blockade in the AS which is effectively a spinal polyenthesitis but evidence for efficacy of IL-23 inhibition for peripheral enthesitis in PsA and preliminary suggestions for benefit in axial PsA, raises many questions. Key amongst these is whether spinal inflammation may exhibit entheseal IL-17A production independent of IL-23 but peripheral enthesitis is largely dependent on IL-23 driven IL-17 production. Furthermore, IL-23 blocking strategies in animal models may prevent experimental SpA evolution but not prevent established disease, perhaps pointing towards a role for IL-23 in innate immune disease initiation whereas persistent disease is dependent on memory T-cell responses that drive IL-17A production independently of IL-23, but this needs further study. Furthermore, IL-12/23 posology in inflammatory bowel disease is substantially higher than that used in AS trials which merits consideration. Therefore, the IL-23 pathway is centrally involved in the SpA concept but the nuances and intricacies in axial inflammation that suggest non-response to IL-23 antagonism await formal definition. The absence of comparative immunology between the different skeletal sites renders explanations purely hypothetical at this juncture.

Crossing the barriers: Revisiting the gut feeling in rheumatoid arthritis

To avoid autoimmunity, it is essential to keep the balance between the defence against pathogens and the maintenance of tolerance to self-antigens. Mucosal inflammation may lead to breakdown of tolerance and activation of autoreactive cells. Growing evidence suggests a major contribution of gut microbiota to the onset of chronic, autoimmune inflammatory diseases including rheumatoid arthritis (RA). RA patients show significant differences in the composition of gut microbiota compared to healthy controls, and in murine arthritis models certain bacteria can induce inflammatory Th17 responses or autoantibody production. The gut microbiota plays an important role in regulating the balance between immunogenic and tolerogenic immune responses. The intestinal barrier is the site of the body where most host-microbiota interaction takes place. Certain microbiota or their metabolites can cause a break in homeostasis by affecting the intestinal barrier integrity and permeability. However, an intact intestinal barrier is essential to separate the intestinal epithelium from toxins, microorganisms, and antigens in the gut lumen. This review will focus on the correlation between a leaky gut and the onset of arthritis. Furthermore, it will be discussed how targeting the intestinal barrier function by dietary changes might provide an opportunity to modulate the development of RA.

From the Genetics of Ankylosing Spondylitis to New Biology and Drug Target Discovery

Genome-wide association studies (GWAS) have identified 113 single nucleotide polymorphisms (SNPs) affecting the risk of developing ankylosing spondylitis (AS), and an on-going GWAS study will likely identify 100+ new risk loci. The translation of genetic findings to novel disease biology and treatments has been difficult due to the following challenges: (1) difficulties in determining the causal genes regulated by disease-associated SNPs, (2) difficulties in determining the relevant cell-type(s) that causal genes exhibit their function(s), (3) difficulties in determining appropriate cellular contexts to interrogate the functional role of causal genes in disease biology. This review will discuss recent progress and unanswered questions with a focus on these challenges. Additionally, we will review the investigation of biology and the development of drugs related to the IL-23/IL-17 pathway, which has been partially driven by the AS genetics, and discuss what can be learned from these studies for the future functional and translational study of AS-associated genes.

Microbial-derived antigens and metabolites in spondyloarthritis

Spondyloarthritis (SpA) is a group of chronic, immune-mediated, inflammatory diseases affecting the bone, synovium, and enthesis. Microbiome, the community of microorganisms that has co-evolved with human hosts, plays a pivotal role in human health and disease. This invisible "essential organ" supplies the host with a myriad of chemicals and molecules. In turn, microbial metabolites can serve as messengers for microbes to communicate with each other and in the cross-talk with host cells. Gut dysbiosis in SpA is associated with altered microbial metabolites, and an accumulated body of research has contributed to the understanding that changes in intestinal microbiota can modulate disease pathogenesis. We review the novel findings from human and animal studies to provide an overview of the contribution of individual microbial metabolites and antigens to SpA.

Treatment strategies in axial spondyloarthritis: what, when and how?

There have been major advances in the management of axial spondyloarthritis (axSpA) with the introduction of effective biologic agents targeting TNF and IL-17A. Clinicians now have more choice but, despite treatment recommendations, are still faced with significant uncertainty when deciding on the optimal treatment strategy for an individual patient in clinical practice. Management of axSpA typically requires both non-pharmacological and pharmacological interventions. NSAIDs remain the first line drug therapies for axSpA with proven efficacy for symptomatic management but uncertainty remains regarding their optimal long-term use relating to radiographic progression and safety in axSpA. To-date there are no head-to-head trials of biologics in axSpA. Clinicians need to consider other factors, including extra-articular manifestations, comorbidities, safety and radiographic progression when deciding on which biologic to recommend for an individual patient. This article will explore the evidence relating to these factors and highlight areas of unmet need.

Treatment of Juvenile Spondyloarthritis: Where We Stand

Juvenile spondyloarthritis is a subset of juvenile idiopathic arthritis (JIA) with onset in late childhood and adolescence and a strong association with human leukocyte antigen (HLA) B-27 positivity and familial aggregation that has the potential for axial involvement, potentially leading to ankylosing spondylitis. Current therapy for severe disease relies heavily on tumor necrosis factor inhibitors (TNFi). Treatment paradigms in children largely consist of extrapolation from studies on adults with spondyloarthritis. Additional therapies studied in adults include non-steroidal anti-inflammatory drugs (NSAIDs), blockade of the interleukin-17 (IL-17) and IL-23 axes, blockade of T-cell stimulation, phosphodiesterase (PDE)-4 inhibition, and Janus-activated kinase (JAK) pathway alteration. IL-17 blockade and IL-23 blockade are guideline approved after TNFi failure (and even as an alternative to TNFi) in adults, depending on concomitant inflammatory bowel and skin disease, with JAK and PDE-4 inhibition options following biologic failure. Neither pediatric nor adult guidelines address IL-6 blockade, T-cell co-stimulation blockade, or combination biologic therapy.

Gut Microbiome and Its Interaction with Immune System in Spondyloarthritis

Emerging evidence suggests there is a gut-joint axis in spondyloarthritis (SpA). In a study, subclinical gut inflammation occurred in nearly 50% of SpA. Chronic gut inflammation also correlated with disease activity in SpA. Trillions of microorganisms reside in the human gut and interact with the human immune system. Dysbiosis affects gut immune homeostasis and triggers different autoimmune diseases including SpA. The absence of arthritis in HLA-B27 germ-free mice and the development of arthritis after the introduction of commensal bacteria to HLA-B27 germ-free mice proved to be the important role of gut bacteria in shaping SpA, other than the genetic factor. The recent advance in gene sequencing technology promotes the identification of microorganisms. In this review, we highlighted current evidence supporting the link between gut and axial SpA (axSpA). We also summarized available findings of gut microbiota and its interaction with the immune system in axSpA. Future research may explore the way to modulate gut microorganisms in axSpA and bring gut microbiome discoveries towards application.

Non-radiographic axial spondyloarthritis

Non-radiographic axial spondyloarthritis (nr-axSpA) is a subgroup of axial spondyloarthritis (axSpA) without fulfilling the modified New York criteria of sacroiliac joint radiographs for ankylosing spondylitis (AS). AS and nr-axSpA share various demographic and clinical features and disease burden, although sex and objective inflammatory findings such as elevated serum C-reactive protein level are slightly different between AS and nr-axSpA. Recently, diagnostic guidance for nr-axSpA in Japan was proposed for epidemiological studies of a population with a low prevalence of HLA-B27 positivity and the use of molecular targeted agents suitable for the unique medical care system in Japan. A biological agent targeting interleukin-17 was approved for nr-axSpA by the Pharmaceutical and Medical Devices Agency (PMDA) in August 2020. Some other biological agents will be also available for Japanese patients with nr-axSpA in the near future.

Applying precision medicine to unmet clinical needs in psoriatic disease

Psoriatic disease (PsD) is a heterogeneous condition that can affect peripheral and axial joints (arthritis), entheses, skin (psoriasis) and other structures. Over the past decade, considerable advances have been made both in our understanding of the pathogenesis of PsD and in the treatment of its diverse manifestations. However, several major areas of continued unmet need in the care of patients with PsD have been identified. One of these areas is the prediction of poor outcome, notably radiographic outcome in patients with psoriatic arthritis, so that stratified medicine approaches can be taken; another is predicting response to the numerous current and emerging therapies for PsD, so that precision medicine can be applied to rapidly improve clinical outcome and reduce the risk of toxicity. In order to address these needs, novel approaches, including imaging, tissue analysis and the application of proteogenomic technologies, are proposed as methodological solutions that will assist the dissection of the critical immune-metabolic pathways in this complex disease. Learning from advances made in other inflammatory diseases, it is time to address these unmet needs in a multi-centre partnership aimed at improving short-term and long-term outcomes for patients with PsD.

Smoking in spondyloarthritis: unravelling the complexities

Tobacco smoking is a major threat to health. There is no doubt about the need to promote and support cessation at every opportunity. Smoking has a clear role in RA, but what evidence is there that the same relationship exists in SpA? In this review, we examine (the less cited) paradoxes and contradictions in the existing axial SpA (axSpA) and PsA literature; for example, smoking appears to be 'protective' for some axSpA manifestations. We also highlight findings from higher quality evidence: smoking is associated with increased risk of PsA and the risk of psoriasis in axSpA. The relationship between smoking and SpA is far from simple. Our aim is to highlight the harms of smoking in SpA and bring attention to inconsistencies in the literature to inform further research.

BSR Spondyloarthritis Course, 27 February 2020. Spondyloarthritis: pathogenesis, diagnosis and management

High-quality continuous medical education is essential to maintain excellence in health-care delivery, upskilling professionals and improving patient outcomes. This is particularly relevant when addressing rare disease groups, such as the spondyloarthritides, a group of heterogeneous inflammatory conditions that affect joints and other organs, such as the skin, bowel and eye. Professional bodies, such as the British Society for Rheumatology (BSR), are well placed to deliver this type of education. In 2020, the BSR ran a dedicated SpA course aimed at rheumatology health-care professionals wishing to update their basic knowledge of SpA with a review of the latest advances in the field. Here, we summarize the proceedings of the meeting and discuss the value of such an initiative.

New developments in our understanding of ankylosing spondylitis pathogenesis

Ankylosing spondylitis (AS) is a common immune‐mediated inflammatory arthritis with a strong genetic predisposition. We review recent data from genetic and animal studies highlighting the importance of Type 17 immune responses. Furthermore, the efficacy (or lack thereof) of different anti‐cytokine monoclonal antibodies has highlighted the diversity of Type 17 immune cells and cytokines critical to AS and related spondyloarthritis pathogenesis. Recent studies have strongly implicated the gut microbiome in AS. Finally, we propose that the local metabolic environment of the joint may have a key role in driving AS, and present a novel model of AS pathogenesis.