No efficacy of anti-IL-23 therapy for axial spondyloarthritis in randomised controlled trials but in post-hoc analyses of psoriatic arthritis-related 'physician-reported spondylitis'?

The Evaluation of Effectiveness and Safety of Guselkumab in Patients with Psoriatic Arthritis in a Prospective Multicentre "Real-Life" Cohort Study

INTRODUCTION

Guselkumab is an interleukin-23 (IL-23) inhibitor licensed for the treatment of psoriatic arthritis (PsA). This study aimed to evaluate the 6-month effectiveness of guselkumab in patients with PsA in a "real-life" multicentre patient cohort. We also estimated the drug retention rate (DRR) of gusulkumab, also assessing the impact of comorbidities and patient clinical characteristics, in a collective 18-month prospective follow-up.

METHODS

Between December 2021 and September 2023, consecutive patients with PsA were evaluated if treated at least for 6 months with guselkumab in a prospective multicentre study to evaluate the effectiveness of the drug by means of disease activity index for psoriatic arthritis (DAPSA) and cumulative DRR.

RESULTS

A total of 111 patients with PsA were evaluated and treated with guselkumab (age 56.8 ± 9.9, male sex 20.7%). These patients were mainly characterised by active and long-standing PsA with median disease duration of 6.0 (7.0) years (55.9% disease duration ≥ 5 years), 55.0% showed comorbidities, 78.4% of patients were previously treated with biologic disease-modifying anti-rheumatic drugs (bDMARDs), and 60.4% concomitantly with conventional synthetic DMARDs (csDMARDs). After 6 months, a significant reduction of DAPSA was observed (β - 15.47, p = 0.001, 95% CI - 23.15 to - 9.79) with 39.6% of patients achieving a DAPSA ≤ 14. At the end of cumulative follow-up, 71.2% of patients were still treated with guselkumab whereas 24.3% discontinued the drug because of inefficacy. An 18-month DRR of guselkumab of 66.7% was estimated with a mean time of administration of 9.8 ± 4.1 months. The results of the DRR were stratified according to patient clinical characteristics. The DRR of guselkumab appeared to be not influenced by long disease duration, comorbidities, obesity, concomitant csDMARDs, and previous bDMARDs.

CONCLUSION

The "real-life" 6-month effectiveness of guselkumab was shown in patients with PsA, mainly characterised by active long-standing disease, previously treated with bDMARDs, and with comorbidities. Furthermore, a good DRR of guselkumab was estimated in the cumulative 18 months of follow-up and appeared to be not influenced by long disease duration, comorbidities, obesity, and previous bDMARDs.

Existing and Emerging Targeted Therapies in Juvenile Psoriatic Arthritis: Challenges and Unmet Needs

Juvenile psoriatic arthritis (JPsA) is a heterogeneous type of non-systemic chronic inflammatory arthritis affecting children and young people. This review focuses on highlighting challenges in harmonising recommendations for the use of available therapies in JPsA, according to its distinct clinical phenotypes, and explores the similarities and differences between the disease classification and management across age. We further explore the emerging therapeutic landscape, summarising the recently completed clinical trials in JPsA, and ongoing studies in both JPsA and adults with psoriatic arthritis, highlighting unmet needs and barriers for translational research in JPsA. The novel therapeutic agents in clinical development in JPsA range from monoclonal antibodies targeting interleukin (IL)-17, IL-12/23 and IL-23 blockades to synthetic small molecules targeting Janus kinase and tyrosine kinase and phosphodiesterase-4 inhibition. In addition, there are head-to-head clinical trials comparing tumour necrosis factor-α blockade with both IL-17 and IL-23 inhibition. Most of these new therapies have been tested in adults with psoriatic arthritis and have advanced to the phase III stage of drug development or received license for use, suggesting promising signals for efficacy and potentially acceptable safety and tolerability for JPsA. Further translational research in JPsA is required to improve our understanding of the impact of age at onset on treatment efficacy, as well as to provide opportunities for better management of refractory disease and improved long-term outcomes in JPsA, for ultimate patient benefit.

Magnetic resonance imaging characteristics in patients with psoriatic arthritis and axial manifestations from the MAXIMISE cohort

OBJECTIVE

The current analysis of the MAXIMISE trial was conducted to investigate the presence of post-inflammatory and degenerative spinal changes and inflammatory changes in spinal processes identified in baseline MRIs and their potential for predicting differential treatment effects in a cohort of PsA patients with axial manifestations.

METHODS

Baseline spinal MRIs from the MAXIMISE trial were re-read to identify additional inflammatory (spinal process), post-inflammatory, and degenerative changes, and investigate the differential treatment effect of these imaging features using logistic regression modelling.

RESULTS

In addition to bone marrow oedema assessed at primary analysis, spinal process inflammation and post-inflammatory changes evaluated by FAt Spondyloarthritis Spine Score were documented in 11.1% and 20.2% patients, respectively. At least one type of degenerative change was noted in 64% patients, with Pfirrmann grade ≥3 (51.1%) being the most common. Combining primary and re-read MRI findings, 67.1% of patients presented with inflammatory or post-inflammatory changes while 21.2% had degenerative changes alone. Although not statistically significant, post-inflammatory changes were associated with a trend for better efficacy outcomes in terms of ASAS20, ASAS40 and BASDAI50 responses; a trend for worse outcomes was observed in the presence of degenerative changes.

CONCLUSION

The current analysis revealed the occurrence of additional inflammatory and post-inflammatory changes suggestive of axial PsA (axPsA) and a trend for better clinical outcomes for patients treated with secukinumab. These results elucidate the imaging characteristics and improve our current understanding of axPsA thereby supporting the interpretation of future trials.

TRIAL REGISTRATION

ClinicalTrials.gov, NCT02721966.

Disease characteristics, pathogenesis, and treatment controversies of axial psoriatic arthritis

Axial psoriatic arthritis (axPsA) has considerable overlap with axial spondyloarthritis (axSpA) but has some unique features that sometimes preclude classification into axSpA. It has some clinical and radiographic differences compared to axSpA. Imaging typically shows asymmetric syndesmophytes, mainly in the cervical spine, with less frequent sacroiliitis. It more commonly presents later in life and is associated with less severe inflammatory back pain than axSpA. The interleukin (IL) IL-23/IL-17 axis is central to the pathogenesis of both diseases. However, the response to therapies targeting these cytokines has been different. IL-23 inhibitors are ineffective in axSpA but may be effective in psoriatic arthritis (PsA). Recent post hoc analyses of clinical trial data with IL-23 inhibitors in PsA have raised the possibility of their efficacy in axPsA and need evaluation in future clinical trials. Moreover, there is a need for classification criteria for axPsA and better tools to assess therapeutic response.

Efficacy of Guselkumab on Axial-Related Symptoms Through up to 2 Years in Adults with Active Psoriatic Arthritis in the Phase 3, Randomized, Placebo-Controlled DISCOVER-2 Study

INTRODUCTION

Guselkumab previously showed greater improvements versus placebo in axial symptoms in patients with psoriatic arthritis (PsA) (assessed by Bath Ankylosing Spondylitis Disease Activity Index [BASDAI] and Ankylosing Spondylitis Disease Activity Score [ASDAS]), in post hoc analyses of the phase 3, placebo-controlled, randomized DISCOVER-1 and DISCOVER-2 studies. We now evaluate durability of response in axial-related outcomes through 2 years of DISCOVER-2.

METHODS

DISCOVER-2 biologic-naive adults with active PsA (≥ 5 tender/ ≥ 5 swollen joints, C-reactive protein ≥ 0.6 mg/dl) were randomized to guselkumab 100 mg every 4 weeks (Q4W) or at week 0, week 4, then Q8W, or placebo → guselkumab Q4W at week 24. Among patients with imaging-confirmed sacroiliitis (investigator-identified), axial symptoms were assessed through 2 years utilizing BASDAI, BASDAI Question #2 (spinal pain), modified BASDAI (mBASDAI; excludes Question #3 [peripheral joint pain]), and ASDAS. Mean changes in scores and proportions of patients achieving ≥ 50% improvement in BASDAI (BASDAI 50) and ASDAS responses, including major improvement (decrease ≥ 2.0), were determined through week 100. Treatment failure rules (through week 24) and nonresponder imputation of missing data (post-week 24) were utilized. Mean BASDAI component scores were assessed through week 100 (observed data). Exploratory analyses evaluated efficacy by sex and HLA-B*27 status.

RESULTS

Among 246 patients with PsA and imaging-confirmed sacroiliitis, guselkumab-treated patients had greater mean improvements in BASDAI, mBASDAI, spinal pain, and ASDAS scores, lower mean BASDAI component scores, and greater response rates in achieving BASDAI 50 and ASDAS major improvement vs. placebo at week 24. Differences from placebo were observed for guselkumab-treated patients in selected endpoints regardless of sex or HLA-B*27 status. At week 100, mean improvements were ~ 3 points for all BASDAI scores and 1.6-1.7 for ASDAS; 49-54% achieved BASDAI 50 and 39% achieved ASDAS major improvement at week 100.

CONCLUSIONS

Guselkumab treatment provided durable and meaningful improvements in axial symptoms and disease activity in substantial proportions of patients with active PsA and imaging-confirmed sacroiliitis.

TRIAL REGISTRATION

Clinicaltrials.gov NCT03158285.

Project Highlights From the GRAPPA 2022 Annual Meeting: Education Initiatives and Axial Involvement in Psoriatic Arthritis

A core mission of the Group for Research and Assessment of Psoriasis and Psoriatic Arthritis (GRAPPA) is to provide education about psoriasis and psoriatic arthritis globally. This is a multifaceted endeavor involving in-person and virtual lectures, discussions, podcasts, and archived videos directed toward clinicians and researchers who are involved with psoriatic disease (PsD) care. In partnership with patient service leagues, we also aim to provide education to patients with PsD. At the 2022 annual meeting, an update of the ongoing and expected educational initiatives was presented. A project with a high educational and research value is the Axial Involvement in Psoriatic Arthritis (AXIS) cohort established in collaboration with the Assessment of Spondyloarthritis international Society (ASAS). Here we summarize the status of the project.

RORγt inhibition ameliorates IL-23 driven experimental psoriatic arthritis by predominantly modulating γδ-T cells

OBJECTIVE

Divergent therapeutic outcomes on different disease domains have been noted with IL-23 and IL-17A-blockade in PsA. Therefore, elucidating the role of RORγt, the master regulator of type 17 immune responses, is of potential therapeutic interest. To this end, RORγt inhibition was assessed in combined skin, joint and gut inflammation in vivo, using a PsA model.

METHODS

We tested the efficacy of a RORγt antagonist in B10.RIII mice challenged with systemic overexpression of IL-23 by hydrodynamic injection of IL-23 enhanced episomal vector (IL-23 EEV). Clinical outcomes were evaluated by histopathology. Bone density and surface erosions were examined using micro-computed tomography. Cytokine production was measured in serum and by intracellular flow cytometry. Gene expression in PsA-related tissues was analysed by qPCR.

RESULTS

RORγt-blockade significantly ameliorated psoriasis, peripheral arthritis and colitis development in IL-23 EEV mice (improvement of clinical scores and weight loss respectively by 91.8%, 58.2% and 7.0%, P < 0.001), in line with profound suppression of an enhanced type IL-17 immune signature in PsA-affected tissues. Moreover, inflammation-induced bone loss and bone erosions were reduced (P < 0.05 in calcaneus, P < 0.01 in tibia). Sustained IL-23 overexpression resulted in only mild signs of sacroiliitis. Gamma-delta (γδ)-T cells, the dominant source of T cell-derived IL-17A and IL-22, were expanded during IL-23 overexpression, and together with Th17 cells, clearly countered by RORγt inhibition (P < 0.001).

CONCLUSION

RORγt-blockade shows therapeutic efficacy in a preclinical PsA model with protection towards extra-musculoskeletal manifestations, reflected by a clear attenuation of type 17 cytokine responses by γδ-T cells and Th17 cells.

Risankizumab for the treatment of active psoriatic arthritis in adults

INTRODUCTION

Psoriatic arthritis (PsA) is a chronic rheumatic disease that displays a variety of clinical manifestations. Although new treatments have emerged over the last 2 decades, challenges remain in controlling inflammation in multiple PsA clinical domains.

AREAS COVERED

Risankizumab, one of the biologic disease modification anti-rheumatic drugs (bDMARDs) that target the interleukin (IL)-23 p19 subunit, was recently approved for PsA worldwide. This review primarily highlights the recent clinical trials of risankizumab covering its physiological evaluation, patient-reported outcomes, and safety profiles in patients with PsA. We also provide evidence for anti-IL-23 therapies against extra-articular manifestations and axial symptoms of PsA. Furthermore, potential distinct efficacies and mechanisms of action in anti-IL-23 therapies are discussed. Overall, risankizumab is effective in a variety of clinical signs and symptoms of PsA regardless of prior bDMARDs experience.

EXPERT OPINION

Accumulating evidence shows that anti-IL-23 drugs, including risankizumab, are promising treatments that can be used as first- or second-line therapies for PsA. However, multiple challenges remain, including confirming efficacy for axial symptoms and identifying the phenotype of specific patients who respond better to risankizumab than other drugs. Lastly, future data focusing on the long-term efficacy and safety of risankizumab beyond the 1-year observation period are also needed.

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.

Comparison of patients with axial PsA and patients with axSpA and concomitant psoriasis: an analysis of the German register RABBIT-SpA

BACKGROUND

Psoriatic arthritis (PsA) and axial spondyloarthritis (axSpA) show certain overlaps: A subset of patients with PsA can develop axial involvement (axial PsA, axPsA), while a subset of patients with axSpA presents with psoriasis (axSpA+pso). Treatment strategy for axPsA is mostly based on axSpA evidence.

OBJECTIVES

To compare demographic and disease-specific parameters of axPsA and axSpA+pso.

METHODS

RABBIT-SpA is a prospective longitudinal cohort study. AxPsA was defined based on (1) clinical judgement by rheumatologists; (2) imaging (sacroiliitis according to modified New York criteria in radiographs or signs of active inflammation in MRI or syndesmophytes/ankylosis in radiographs or signs of active inflammation in spine MRI). axSpA was stratified into axSpA+pso and axSpA without pso.

RESULTS

Psoriasis was documented in 181/1428 axSpA patients (13%). Of 1395 PsA patients, 359 (26%) showed axial involvement. 297 patients (21%) fulfilled the clinical definition and 196 (14%) the imaging definition of axial manifestation of PsA. AxSpA+pso differed from axPsA regardless whether clinical or imaging definition was used. axPsA patients were older, more often female and less often HLA-B27+. Peripheral manifestations were more often present in axPsA than in axSpA+pso, whereas uveitis and inflammatory bowel disease were more common in axSpA+pso. Burden of disease (patient global, pain, physician global) was similar among axPsA and axSpA+pso patients.

CONCLUSIONS

AxPsA differs from axSpA+pso in its clinical manifestations, irrespective of whether axPsA is defined clinically or by imaging. These findings support the hypothesis that axSpA and PsA with axial involvement are distinct entities, so extrapolation of treatment data from randomised controlled trials in axSpA should be performed with caution.

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.

Levofloxacin induces differential effects in the transcriptome between the gut, peripheral and axial joints in the Spondyloarthritis DBA/1 mice: Improvement of intestinal dysbiosis and the overall inflammatory process

To analyze the effect of levofloxacin-induced intestinal microbiota modifications on intestinal, joint, and systemic inflammation in the DBA/1 mice with spontaneous arthritis. The study included two groups of mice, one of which received levofloxacin. The composition and structure of the microbiota were determined in the mice's stool using 16S rRNA sequencing; the differential taxa and metabolic pathway between mice treated with levofloxacin and control mice were also defied. The effect of levofloxacin was evaluated in the intestines, hind paws, and spines of mice through DNA microarray transcriptome and histopathological analyses; systemic inflammation was measured by flow cytometry. Levofloxacin decreased the pro-inflammatory bacteria, including Prevotellaceae, Odoribacter, and Blautia, and increased the anti-inflammatory Muribaculaceae in mice's stool. Histological analysis confirmed the intestinal inflammation in control mice, while in levofloxacin-treated mice, inflammation was reduced; in the hind paws and spines, levofloxacin also decreased the inflammation. Microarray showed the downregulation of genes and signaling pathways relevant in spondyloarthritis, including several cytokines and chemokines. Levofloxacin-treated mice showed differential transcriptomic profiles between peripheral and axial joints and intestines. Levofloxacin decreased the expression of TNF-α, IL-23a, and JAK3 in the three tissues, but IL-17 behaved differently in the intestine and the joints. Serum TNF-α was also reduced in levofloxacin-treated mice. Our results suggest that the microbiota modification aimed at reducing pro-inflammatory and increasing anti-inflammatory bacteria could potentially be a coadjuvant in treating inflammatory arthropathies.

Emerging therapies for the treatment of spondyloarthritides with focus on axial spondyloarthritis

INTRODUCTION

Spondyloarthritides (SpA) such as axial spondyloarthritis (axSpA) including ankylosing spondylitis (AS) and psoriatic arthritis (PsA) including psoriasis are chronic immune-mediated disorders with involvement of tumor necrosis factor (TNF), interleukin (IL)-17 cytokines, and janus kinases (JAK) in their pathogenesis, with IL-23 clearly also playing a role in psoriasis, PsA, and chronic inflammatory bowel diseases.

AREAS COVERED

In this narrative review, we focus on a biologic disease modifying anti-rheumatic drug (bDMARD), the bispecific IL-17A and IL-17 F inhibitor bimekizumab, and a targeted synthetic (ts) DMARD, the JAK inhibitor (i) filgotinib - emerging agents for the treatment of axSpA. Upadacitinib, another JAKi that has recently been reviewed intensively by us is already approved for axSpA and PsA in Europe.

EXPERT OPINION

In contrast to inhibition of IL-17, JAKi also work in rheumatoid arthritis (RA), while agents inhibiting IL-17 are not, even though some effect may be there. Indeed, 4 JAKi including filgotinib are approved for RA. There are several head-to-head trials with bimekizumab in plaque psoriasis. The last one showed that the bispecific inhibition of IL-17A and IL-17 F with bimekizumab may indeed be superior to inhibition of IL-17A alone with 300 mg secukinumab (usual dosage). Whether this is also the case for treatment of axSpA and PsA remains to be shown.

Bibliometric analysis of publications on enthesitis in spondyloarthritis in 2012-2021 based on web of science core collection databases

Enthesitis, a characteristic of spondyloarthritis, has been paid considerable attention by researchers, and numerous enthesitis-related studies have been published in recent years. However, no study has been conducted to analyze enthesitis-related researches with bibliometric methods. This study aimed to provide a broad understanding of enthesitis-related researches and explore the direction of hot topics and future research trends from a bibliometric perspective. The global literatures on enthesitis published from 2012 to 2021 were scanned in the Web of Science Core Collection databases. Visualization and bibliometric analyses were generated by an online bibliometric platform and VOSviewer software to explore the hot topics and research trends. A total of 1,181 documents were included in this study. Publications were mainly from these countries in North America and Western Europe. Among these countries, the United States was the leading country with the maximum publication counts (210), highest h-index (47), and largest collaboration network as of June 29, 2022. The most influential journal and powerful author were Journal of Rheumatology and Professor Mease PJ, respectively. Co-occurrence analysis of keywords identified that "axial spondyloarthritis", "interleukin 23", and "secukinumab" might be the future hotspots. More and more attention had been paid to enthesitis in the past 10 years. Present studies focused on the effect of inflammatory cytokines involved in the pathogenesis and the development of antibodies against these factors. These studies played a key role in understanding the research direction and subsequent management of enthesitis, and helped researchers extract hidden valuable information for further study.

Axial involvement in psoriatic arthritis

Among the variety of clinical manifestations of psoriatic arthritis (PsA) – including peripheral arthritis, dactylitis, enthesitis, and axial disease – spondylitis is the least studied. There is no generally accepted definition of axial PsA (axPsA), nor is there any common terminology or diagnostic criteria for it. In the rheumatology community, there is also no consensus regarding radiological and MRI assessment of axial involvement in PsA patients, while disease activity indexes and the therapeutic tactics are borrowed from those used in treating axial spondyloarthritis (axSpA) and ankylosing spondylitis (AS). However, despite a range of similarities in immunopathogenetic mechanisms of axPsA and axSpA, there are also certain differences that may affect the treatment response in these patients. The aim of this review is the analysis of data on axial disease in PsA. The article discusses the genetic features, clinical presentations, imaging techniques, differential diagnostics and treatment options of axPsA.

Axial Spondyloarthritis: Reshape the Future-From the "2022 GISEA International Symposium"

The term "axial spondyloarthritis" (axSpA) refers to a group of chronic rheumatic diseases that predominantly involve the axial skeleton and consist of ankylosing spondylitis, reactive arthritis, arthritis/spondylitis associated with psoriasis (PsA) and arthritis/spondylitis associated with inflammatory bowel diseases (IBD). Moreover, pain is an important and common symptom of axSpA. It may progress to chronic pain, a more complicated bio-psychosocial phenomena, leading to a significant worsening of quality of life. The development of the axSpA inflammatory process is grounded in the complex interaction between genetic (such as HLA B27), epigenetic, and environmental factors associated with a dysregulated immune response. Considering the pivotal contribution of IL-23 and IL-17 in axSpA inflammation, the inhibition of these cytokines has been evaluated as a potential therapeutic strategy. With this context, here we discuss the main pathogenetic mechanisms, therapeutic approaches and the role of pain in axSpA from the 2022 International GISEA/OEG Symposium.

IL-23 in axial spondyloarthritis and psoriatic arthritis: a good fit for biological treatment?

INTRODUCTION

Interleukin 23 (IL-23) is a pro-inflammatory cytokine that plays a protective role against bacterial and fungal infections. However, the dysregulation of the IL-23/IL-17 axis provides a solid substrate for the development of various inflammatory diseases, such as psoriatic arthritis (PsA) and ankylosing spondylitis (AS).

AREAS COVERED

In different clinical trials, several drugs against IL-23 have shown efficacy and safety towards PsA, with excellent results on skin and joint scores. However, the same drugs did not show the same efficacy in AS, suggesting that IL-23 may not be a relevant driver of the pathobiology and clinical symptoms of active axial spondyloarthritis (axSpA).

EXPERT OPINION

These drugs have shown an excellent efficacy and a good safety profile towards PsA, while in AS the efficacy of the IL-23 blockade is lacking for reasons not yet known. Several hypotheses have been reported, but further studies will be needed for a greater understanding. This suggests the involvement of pathways or mechanisms for the development of SpA that remain unknown. In order to allow a wide use of IL-23 inhibitors, further clinical trials and long-term prospective studies are necessary.

Axial Spondyloarthritis in Japan

PURPOSE OF REVIEW

The differences in the epidemiology and management of patients with axial spondyloarthritis (axSpA) among regions and countries largely depend on the positivity of human leukocyte antigen (HLA)-B27 and the health care system. This review article focused on axSpA in Japan, where the prevalence of HLA-B27 is extremely low (0.3%) and the universal health insurance system typically provides a 70% or more copayment by the government.

RECENT FINDINGS

A nationwide survey was conducted in Japan in 2018, which estimated that there were 3200 patients (95% confidence interval [CI]: 2400-3900) with ankylosing spondylitis (AS), a term interchangeable with radiographic axSpA (r-axSpA), and 800 patients (95% CI: 530-1100) had non-radiographic (nr)-axSpA. These data indicate a prevalence of 2.6/100,000 or 0.0026% for AS and 0.6/100,000 or 0.0006% for nr-axSpA. Patients with AS, but not those with nr-axSpA, are designated as suffering from intractable diseases in Japan; thus, their medical expenses are reduced by grant under the Act on Medical Care for Patients with Intractable Diseases. As of February 2022, infliximab, adalimumab, secukinumab, ixekizumab, and brodalumab have been approved for AS, and secukinumab, ixekizumab, and brodalumab have been approved for nr-axSpA. An algorithm for nr-axSpA in Japan has been developed for the proper diagnosis and use of these therapeutic agents. A low prevalence of axSpA, especially that of nr-axSpA, was found in Japan. Early referral and the resultant diagnosis and appropriate treatment of these patients by rheumatologists are crucial issues in Japan, as in other countries.