Immunotherapy, including the use of immune checkpoint inhibitors (ICI), is now a well-established pillar of cancer therapy. Exploitation of regulatory immune mechanisms through the inhibition of immune checkpoints has led to unprecedented responses in advanced malignancies, heralded as one of the most promising therapeutics in the history of cancer treatment (Hargadon, Johnson, and Williams 2018). Since the FDA approval of ipilimumab for the treatment of metastatic melanoma in 2011, there have been an additional eight ICI to receive regulatory approval for over a dozen different indications (Luke 2025). The success of these agents is tempered by off-target effects which can mimic idiopathic autoimmune diseases, affect all major organ systems, and are termed immune-related adverse events (irAE) (Blidner et al. 2020; Ye et al. 2019; Jamal et al. 2020). The rapidly evolving nature of this field of medicine has presented challenges for oncologists and sub-specialists alike to keep abreast of the vast amount of emerging evidence to optimise the management of patients treated with ICI, particularly those who develop auto-immune toxicities. The role of digital education on clinical competence and practice patterns, in the provision of immunotherapy, has been explored in the oncology setting and shown to be effective (Ackbarali et al. 2021). There have been no such studies looking at the education of rheumatologists on this specific topic. For practicing rheumatologists, navigating not only timely diagnosis and management of de-novo rheumatic irAE (Rh-irAE) but also safety and efficacy of ICI in patients with pre-existing rheumatic disease (PRD) has proven to be a unique challenge. Recent surveys of rheumatologists in the United States, France and Canada have revealed that many lack experience and confidence in the management of these patient populations (Maltez et al. 2019; Kostine et al. 2019). The paramount question, of how the rheumatology community will meet the urgent need for education on this topic, to ensure they are optimally positioned to manage this patient population in coalition with oncology partners, remains unanswered (Calabrese and Mariette 2018). Continuing medical education in such a rapidly evolving field requires unique educational tools with the capacity to easily adapt as new evidence becomes available. We developed a web-based educational platform (www.canrio.ca) to house learning materials for practicing rheumatologists and to facilitate national and international collaboration within both the clinical and research community. As part of this educational initiative, we created five case-based learning modules on the topics of ICI-related inflammatory arthritis (ICI-IA), myositis (ICI-myositis), vasculitis (ICI-vasculitis), sarcoid-like reactions (ICI-SLR), and the management of patients with PRD (ICI-PRD). In addition, case-based rounds accessible to any health-care provider around the world were initiated in May 2021 to provide a forum for cross-discipline, and regional collaboration in problem-solving difficult cases. The overarching goal of the project was to improve knowledge, confidence, and awareness of rheumatic complications of cancer immunotherapy in practicing rheumatologists and to ultimately improve the care of patients with Rh-irAE and PRD receiving ICI. We followed the steps outlined by Grienbenow et al. to guide the development and delivery of continuing medical education (CME) and ensure that all key steps were addressed (Griebenow et al. 2017). This framework was designed to provide a description of the roles and responsibilities of stakeholders involved in the different stages of planning, delivery, and evaluation of CME. For this project, content experts including CanRIO specialists, medical oncologists and a pharmacist were involved in the development and delivery of the CME programme. It has been disseminated to rheumatologists across Canada through the Canadian Rheumatology Association (CRA) and to Oncologists through the Canadian Association of Medical Oncologists (CAMO). Five content experts developed interactive case-based learning modules on the topics of ICI-IA, ICI-myositis, ICI-vasculitis, ICI-SLR and ICI-PRD. Modules included information regarding ICI mechanism of action and the presentation, management, and prognosis of Rh-irAE and in the case of the PRD module, both safety and efficacy of ICI in this patient population. Pre- and post-module tests were administered with each learning module and consisted of 10 identical multiple-choice questions to assess immediate knowledge acquisition. Knowledge transfer was assessed by comparing the pre- and post-module tests. An educational platform, www.canrio.ca, was developed to house the learning modules and other educational content and resources such as registration for interactive virtual case rounds, an up-to-date compilation of relevant research, patient resources, healthcare provider resources and a list of rheumatologists with expertise in the management of these patients practicing across Canada. Google Analytics was embedded within the website and used to track website traffic, including user location. At the time of case-round registration, demographic information regarding the profession, years in practice and experience in the management of these patients was collected. Descriptive statistics are reported as median and interquartile range for non-normal continuous variables and frequency and proportions for categorical variables. Normal distribution was evaluated with the Shapiro-Wilk distribution test and module test scores did not follow a normal distribution. Pre- and post-module test scores were paired and then compared using the non-parametric Wilcoxon signed rank test to assess immediate knowledge retention. Statistical significance was defined as a two-sided p value less than 0.05. Statistical analysis was completed using Stata 17 (StataCorp 2021). From February 2021 to August 2024, 4458 users from 99 different countries accessed the educational platform (www.canrio.ca). The top three countries from which users accessed the site were Canada, the United States and China (Figure 1). A total of 92 people, from Canada, the United States, France and the Netherlands have registered for case rounds since their inception. Most participants were rheumatologists (41%) or trainees (43%). Trainees in oncology, internal medicine and neurology as well as oncologists, research coordinators, and pharmacists also participated in the interactive case rounds. Of the 92 individuals who registered for rounds, 68% were in practice < 5 years and 32% were in practice over 5 years. The level of experience in managing patients on ICIs varied, with 73% of individuals having managed fewer than 5 such patients, 16% 5–15 patients and 11% more than 15 patients. Map of locations from which users have accessed the www.canrio.ca website between February 2021 and August 2024. There were a total of 169 pre-module test entries. A total of 45 individuals completed the ICI-IA module, 42 the ICI-vasculitis module, 34 the ICI-PRD module, 28 the ICI-myositis module and 20 the ICI-SLR module. There were a total of 112 completed post-module test entries across these 5 modules. The median test scores increased from 4 to 7 out of 10 (50%–88%, p < 0.0001) for the ICI-IA module, from 5 to 6 (63%–75%, p = 0.093) for the ICI-myositis module, 4 to 7 (50%–88%, p < 0.0001) for the ICI-PRD module, 3.5 to 7 (38%–88%, p = 0.001) for the ICI-SLR module and 3 to 6 (38%–75%, p < 0.0001) for the ICI-vasculitis module, with the improvement between pre- and post-module scores reaching statistical significance in all but the ICI-myositis module (Figure 2). Box plots of pre-test entries with paired post-test entries for the five modules. (a) ICI-inflammatory arthritis; (b) ICI-myositis; (c) ICI-pre-existing rheumatic disease; (d) ICI-vasculitis; (e) ICI-sarcoid-like reactions. This study showed that baseline knowledge of common RhirAE issues is suboptimal, but that a web-based education platform is an effective tool to increase knowledge dissemination regarding Rh-irAE. The learning modules were successful in generating immediate knowledge acquisition and the website and case rounds reached an international target audience of predominantly rheumatologists. To optimise patient outcomes, clinicians need to be aware of the most current evidence to guide the management of rheumatic complications of immunotherapy. This has historically been challenging, given the rapidly evolving nature of this area of medicine, with another major barrier being the absence of an easily accessible resource housing the most up-to-date evidence. This is the first web-based educational platform to address the urgent unmet need to educate the medical community on rheumatic complications of cancer immunotherapy. This platform has enabled health care-providers from all around the world to have equitable access to high quality, free educational resources. Given the overwhelming quantity of literature and the time restraints physicians are faced with on a day-to-day basis continuing medical education (CME) must be convenient, concise, and clinically relevant. Physicians are increasingly turning to web-based educational initiatives to meet their learning needs, which have been shown to be more effective and efficient than traditional didactic educational sessions (Cullen et al. 2019). It has been consistently shown in studies on CME effectiveness that multiple exposures are more effective than a single exposure and that interactive techniques, including those employed in a case-based rounds, are more effective and may lead to both improved physician performance and patient outcomes (Cervero and Gaines 2015). In addition, CME activities that use multiple educational techniques have been shown to have a greater overall positive effect than those that use a single technique (Cervero and Gaines 2015). In creating this educational platform, we incorporated these aspects of CME that are proven most effective through the utilisation of live media and the incorporation of multiple interactive educational techniques including both enduring material and access to case rounds. Comparison of pre- and post-module test scores confirmed that the learning modules were effective in immediate knowledge acquisition. Furthermore, this platform has provided a unique opportunity for collaboration across both geographic locations and disciplines through participation in the case rounds. A recent scoping review exploring the advantages and disadvantages of virtual CME reported opportunities for collaboration as one of the most cited advantages by participants (Cheng et al. 2023). A limitation of this study was the lack of data on whether this knowledge dissemination has ultimately impacted physician practices or patient outcomes, as assessment of these elements of knowledge translation was beyond the scope of this study. Furthermore, at present, our educational resources are only available in English; however, the amount of global website traffic has highlighted the need for translation into other languages. In summary, the CanRIO website, a comprehensive knowledge dissemination platform on Rh-irAE of cancer immunotherapy, has been accessed by the global medical community. Further research is needed to evaluate whether this knowledge dissemination will lead to changes in physician practice and patient outcomes. Future initiatives will continue to foster international collaboration from a clinical, education and research perspective. Janet Roberts: conceptualization, data curation, formal analysis, funding acquisition, methodology, investigation, methodology, project administration, resources, software, validation, visualization, writing–original draft, writing–review & editing. Shahin Jamal: conceptualization, data curation, funding acquisition, methodology, writing–review & editing, visualization, resources. Marie Hudson: conceptualization, data curation, funding acquisition, methodology, writing–review & editing, visualization, resources. Steven Katz: conceptualization, data curation, funding acquisition, methodology, writing–review & editing, visualization, resources. Daniel Ennis: conceptualization, data curation, funding acquisition, methodology, writing–review & editing, visualization, resources. Nancy Maltez: conceptualization, data curation, funding acquisition, methodology, writing–review & editing, visualization, resources. Keith Lau: formal analysis, methodology, validation, writing–review & editing. Carrie Ye: conceptualization, data curation, formal analysis, funding acquisition, methodology, investigation, methodology, project administration, resources, software, validation, visualization, writing–original draft, writing–review & editing. This study was exempt from the research ethics board review. The authors declare no conflicts of interest. The data that support the findings of this study are available from the corresponding author upon reasonable request.

Idiopathic inflammatory myopathies (IIM), or myositis, are a heterogeneous group of autoimmune disorders that can affect multiple organs, including the muscles, skin, joints, lungs, heart, and gastrointestinal tract. While new-onset myositis has been reported following SARS-CoV-2 infection, cases associated with COVID-19 vaccination remain rare. We describe a unique case of severe progressive edematous facial myositis resembling angioedema in a 22-year-old man, with onset one to two weeks after receiving dual SARS-CoV-2 and influenza vaccinations. This ultimately led to a diagnosis of systemic inflammatory myositis with extensive involvement of proximal muscles in the arms and legs. We outline the clinical course, diagnostic investigations, and treatments, and discuss the potential molecular mechanisms and existing literature on inflammatory myositis induced by SARS-CoV-2 infection or mRNA-based vaccination.

Background In 2020, the Canadian Vasculitis Research Network (CanVasc) published their updated recommendations for the management of antineutrophil cytoplasm antibody (ANCA)-associated vasculitides (AAV). Since then, clinical data on the complement C5a receptor inhibitor avacopan (formerly, CCX168) has continued to expand. Objectives The current addendum provides further recommendations regarding the use of avacopan in AAV based on a review of newly available evidence. Methods An updated systematic literature review on avacopan using Medline, Embase, and the Cochrane Library was performed for publications up to September 2022. New recommendations were developed and categorized according to the EULAR grading levels, as done for previous CanVasc recommendations. A modified Delphi procedure and videoconferences were used to reach ≥80% consensus on the inclusion, wording and grading of each recommendation. Results Three new recommendations were developed. They focus on avacopan therapy indication and duration, as well as timely glucocorticoid tapering. Conclusion These 2022 addended recommendations provide rheumatologists, nephrologists, and other specialists caring for patients with AAV with guidance for the use of avacopan, based on current evidence and consensus from Canadian experts. References [1]Jayne DRW, Merkel PA, Schall TJ, Bekker P; ADVOCATE Study Group. Avacopan for the Treatment of ANCA-Associated Vasculitis. N Engl J Med. 2021;384(7):599-609. [2]Jayne DRW, Bruchfeld AN, Harper L, et al. Randomized Trial of C5a Receptor Inhibitor Avacopan in ANCA-Associated Vasculitis. J Am Soc Nephrol. 2017;28(9):2756-2767. [3]Merkel PA, Niles J, Jimenez R, et al. Adjunctive Treatment With Avacopan, an Oral C5a Receptor Inhibitor, in Patients With Antineutrophil Cytoplasmic Antibody-Associated Vasculitis. ACR Open Rheumatol. 2020;2(11):662-671. [4]van Leeuwen JR, Bredewold OW, van Dam LS, et al. Compassionate Use of Avacopan in Difficult-to-Treat Antineutrophil Cytoplasmic Antibody-Associated Vasculitis. Kidney Int Rep. 2021;7(3):624-628. [5]Gabilan C, Pfirmann P, Ribes D, et al. Avacopan as First-Line Treatment in Antineutrophil Cytoplasmic Antibody-Associated Vasculitis: A Steroid-Sparing Option. Kidney Int Rep. 2022;7(5):1115-1118. [6]Mendel A, Ennis D, Go E, et al. CanVasc Consensus Recommendations for the Management of Antineutrophil Cytoplasm Antibody-associated Vasculitis: 2020 Update. J Rheumatol. 2021;48(4):555-566. Acknowledgements CanVasc wishes to acknowledge the work of Matt Adamson, Sarah Ali, Susanne Benseler MD, Jean-Philippe Bergeron MD, Stephanie Garner MD, Majed Khraishi MD, and Frédéric Morin MD for their additional input on the final draft of the recommendations. Disclosure of Interests David Turgeon: None declared, Volodko Bakowsky Speakers bureau: Abbvie, Consultant of: Advisory board attendance from Abbvie, Apotex, Eli Lily, Novartis, Pfizer, Jamp, and Sandoz UCB, Corisande Baldwin: None declared, David Cabral: None declared, Marie Clements-Baker Speakers bureau: Honoraria from Abbvie, Novartis, Boehringer Ingleheim and Otsuka, Alison Clifford Speakers bureau: Hoffman La-Roche Limited, Consultant of: Participation in clinical trials with Abbvie and UCB, Jan Willem Cohen Tervaert Speakers bureau: Pfizer, Sanofi, AbbVie, Hoffmann-La Roche, Medexus, and GSK, Paid instructor for: Chair IDMC InflaRx (2017-2022), Consultant of: Merck, Novartis, and Mallinckrodt Pharmaceuticals, Natasha Dehghan: None declared, Daniel Ennis: None declared, LEILANI FAMORCA: None declared, Aurore Fifi-Mah Speakers bureau: ChemoCentryx, Grant/research support from: Roche, Louis-Philippe Girard: None declared, Frédéric Lefebvre: None declared, Patrick Liang Grant/research support from: Roche, Amgen, Janssen, Abbvie, BMS, and Novartis, Jean-Paul Makhzoum Speakers bureau: Teva, Otsuka Pfizer, GKS, and Jansenn, David Massicotte-Azarniouch: None declared, Arielle Mendel: None declared, Nataliya Milman Consultant of: Otsuka, Heather Reich Consultant of: Calliditas, Novartis, Pfizer, Eledon, Omeros, Travere and Chinnook, David Robinson: None declared, Carolyn Ross: None declared, Dax G. Rumsey Consultant of: AbbVie, Mylan, and Novartis, Grant/research support from: Pfizer, Medha Soowamber: None declared, Tanveer Towheed: None declared, Judith Trudeau Consultant of: Hoffman-Laroche, Medexus, and ChemoCentryx, Marinka Twilt: None declared, Elaine Yacyshyn: None declared, Gozde Yardimci: None declared, [Nader Khalidi} Consultant of: Roche, Bristol Meyers Squibb, Lillian Barra Consultant of: Roche, Bristol-Myers Squibb, Boehringer-Ingelheim, Otsuka and Pfizer, Grant/research support from: Pfizer, Christian Pagnoux Speakers bureau: ChemoCentryx, Astra-Zeneca, and InflaRx GmbH, Grant/research support from: Roche, GSK, Otsuka, Pfizer.

OBJECTIVE:In 2020, the Canadian Vasculitis Research Network (CanVasc) published their updated recommendations for the management of ANCA-associated vasculitides (AAV). The current addendum provides further recommendations regarding the use of avacopan in AAV based on a review of newly available evidence. METHODS:An updated systematic literature review on avacopan (formerly, CCX168) using Medline, Embase, and the Cochrane Library was performed for publications up to September 2022. New recommendations were developed and categorized according to the EULAR grading levels, as done for previous CanVasc recommendations. A modified Delphi procedure and videoconferences were used to reach ≥80% consensus on the inclusion, wording and grading of each recommendation. RESULTS:Three new recommendations were developed. They focus on avacopan therapy indication and duration, as well as timely glucocorticoid tapering. CONCLUSION:These 2022 addended recommendations provide rheumatologists, nephrologists and other specialists caring for patients with AAV with guidance for the use of avacopan, based on current evidence and consensus from Canadian experts.

Raynaud's phenomenon (RP) is common in rheumatic diseases. In the setting of systemic sclerosis (SSc), it can be complicated by digital ischemia that includes ulceration and gangrene. Systemic adverse effects may preclude the use of oral or topical vasodilators for the treatment of RP and its complications. In this article, we review effectiveness/efficacy of botulinum toxin injection in primary and secondary RP. We discuss botulinum toxin formulations, dosage, sites of administration, and adverse effects. The evidence for botulinum toxin in the treatment of primary and SSc-associated RP is promising. Consistency across patient populations, treatment options (botulinum serotype, dose, and injection site), and outcome measures will be essential for further research.

BACKGROUND/OBJECTIVE:High-dose glucocorticoids (GCs) are required in the initial treatment of systemic vasculitis. However, slow or delayed tapering can lead to unnecessary GC exposure and toxicity. In this quality improvement initiative, we aimed to increase appropriate GC tapering among newly referred patients awaiting specialty consultation at a tertiary vasculitis clinic.METHODS:For each patient referred for anti-neutrophil cytoplasm antibody-associated vasculitis (AAV) or large vessel vasculitis (LVV), recommendation-based GC tapering suggestions were faxed to referring physicians. To maximize uptake, the intervention format was modified according to feedback from referring physicians' offices. The proportion of new patients presenting to their first appointment who (1) had started to taper GCs, (2) were taking their target GC dose according to recommendations, (3) experienced a vasculitis flare during tapering were compared before (July 2017-January 2019) and after (February-October 2019) the intervention.RESULTS:Among 169 consecutive patients referred for AAV or LVV, the proportion who had started to taper GCs by their first visit increased from 84 of 117 (72%) preintervention to 49 of 52 (94%) postintervention (p < 0.01). Mean daily prednisone dose at first visit decreased from 29.9 (SD, 18) mg to 21.7 (SD, 14) mg (p < 0.01). However, the proportion who were ultimately taking "target" GC doses at their first visit did not significantly increase (72% vs. 77%). Disease flares during tapering were similar before and after the intervention (9% vs. 12%).CONCLUSIONS:Patients with AAV and LVV had increased GC tapering and lower GC doses at first visit following a preappointment intervention. Further strategies are needed to improve timely GC tapering in vasculitis.

Objective. Glucocorticoids (GC) remain integral to large-vessel vasculitis (LVV) and ANCA-associated vasculitis (AAV) treatment. We aimed to assess real-world GC tapering trajectories among patients referred for LVV or AAV and identify factors associated with 'delayed' tapering. Methods. Patients first assessed at a vasculitis clinic July 2017-August 2019 for LVV or AAV and taking GC were included. Delayed tapering was defined as prednisone >10 mg above target based on tapering recommendations (2010 British Society of Rheumatology Guidelines for Giant Cell Arteritis, 2015 CanVasc AAV Recommendations). We compared characteristics of patients with delayed and appropriate tapering and assessed barriers to timely tapering though chart reviews and referring physician surveys. Results. 160 patients (65 LVV, 95 AAV) were taking GC at their first visit. Among the 42 (26%) patients with delayed tapering, mean daily prednisone dose was 39.2 mg (SD 14) compared to a target of 15.2 mg (SD 15). Pulse GC were administered to 19/42 (45%) patients with delayed tapering compared to 26/118 (22%) with appropriate tapering (p<0.05). Mean Birmingham Vasculitis Activity Score at treatment onset and GC duration were not significantly different between the two groups. Vision loss and/or stroke was more frequent in LVV referrals who experienced delayed (9/21, 43%) vs. appropriate (6/44, 14%) tapering (p<0.05). Managing risk of vasculitis flare was the most common challenge to tapering GC among surveyed referring physicians. Conclusion. In one quarter of patients referred for LVV or AAV taking GC, tapering was slower than recommended. Promoting timely tapering may reduce GC toxicity.

OBJECTIVE:In 2015, the Canadian Vasculitis Research Network (CanVasc) created recommendations for the management of antineutrophil cytoplasm antibody (ANCA)-associated vasculitides (AAV) in Canada. The current update aims to revise existing recommendations and create additional recommendations, as needed, based on a review of new available evidence.METHODS:A needs assessment survey of CanVasc members informed questions for an updated systematic literature review (publications spanning May 2014 to September 2019) using Medline, Embase, and Cochrane. New and revised recommendations were developed and categorized according to the level of evidence and strength of each recommendation. The CanVasc working group used a 2-step modified Delphi procedure to reach > 80% consensus on the inclusion, wording, and grading of each new and revised recommendation.RESULTS:Eleven new and 16 revised recommendations were created and 12 original (2015) recommendations were retained. New and revised recommendations are discussed in detail within this document. Five original recommendations were removed, of which 4 were incorporated into the explanatory text. The supplementary material for practical use was revised to reflect the updated recommendations.CONCLUSION:The 2020 updated recommendations provide rheumatologists, nephrologists, and other specialists caring for patients with AAV in Canada with new management guidance, based on current evidence and consensus from Canadian experts.

Granulomatosis with polyangiitis (GPA) is a rare antineutrophil cytoplasm antibody-associated vasculitis. Several therapeutic advances have occurred over the past two decades, but relapse rate remains high and refractory cases are not uncommon. Here, we present the case of a female patient diagnosed with GPA at the age of 9 years with a severe, multirelapsing disease course which failed to adequately respond to conventional therapies. Avacopan, a novel C5a receptor inhibitor, was started based on phase II studies that showed promise as a steroid-sparing adjunct. The patient was able to successfully reduce her glucocorticoid dose and reduce her immunosuppressive treatments without another flare. She has been on avacopan for 35 months, had no adverse events that required its discontinuation, and her disease is in sustained remission.

Objective: Although immune checkpoint inhibitors (ICI) have revolutionized cancer therapy, their use is associated with immune toxicities referred to as immune-related adverse events (irAE). Here we describe the clinical presentation and management of rheumatic immune-related adverse events (Rh-irAE) in a national multicenter cohort. Methods: All patients presenting with Rh-irAE at 9 academic sites across Canada between January 2013 and January 2019 were identified and included in this retrospective cohort study. Standardized data were extracted by chart review. Results: 117 patients who developed 136 Rh-irAE were identified. The most frequent Rh-irAE was symmetric polyarthritis (n = 45). Other Rh-irAE included non-inflammatory musculoskeletal symptoms (n = 18), polymyalgia rheumatica (n = 17) and myositis (n = 9). Prednisone was the most commonly used treatment (n = 76) with a mean maximum dose of 60 +/- 74 mg/d and duration of treatment of 8.4 +/- 11 months. Forty-two patients required conventional synthetic disease-modifying anti-rheumatic drugs (DMARD) and two required biologic DMARD to control the Rh-irAE. ICI was discontinued due to the Rh-irAE in 22 patients. There were no deaths related to Rh-irAE. Treatment of the Rh-irAE did not appear to negatively impact the tumor response to immunotherapy with 23 patients experiencing tumor progression prior to treatment of the Rh-irAE and 13 following treatment. Conclusion: In this largest multi-center cohort of Rh-irAE described to date, symmetric polyarthritis was the most common Rh-irAE. There was considerable heterogeneity of treatment, although this did not appear to negatively impact the anti-tumor response. This study can inform the development of evidence-based recommendations to optimize Rh-irAE and cancer outcomes in patients treated with ICI.

ABSTRACT Introduction: Eosinophilic granulomatosis with polyangiitis (EGPA) is a rare antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis characterized by asthma, hypereosinophilia, and progressive multiorgan involvement. Although not fully elucidated, advancement in our understanding of the pathophysiology of EGPA has led to the development of multiple new treatment targets. Areas covered: Herein we review the epidemiology, clinical manifestations, pathophysiology, treatments, and ongoing research in the management of EGPA. The central role of Interleukin-5 (IL-5) in the development and maintenance of hypereosinophilia will be discussed. The value of mepolizumab, an anti-IL-5 monoclonal antibody, in the treatment of EGPA is reviewed in detail. Expert Opinion: The available literature supports the use of mepolizumab for the induction and maintenance of remission of refractory, relapsing, or glucocorticoid-dependent EGPA with potentially greater benefit in those who are ANCA-positive or those with greater eosinophilia (150 cells/L). Despite these positive results, relapses remain frequent, and the need for both short- and long-term glucocorticoid use remains common. More research is needed to address these needs and determine the precise role of mepolizumab. Trial registration: ClinicalTrials.gov identifier: NCT00266565. Trial registration: ClinicalTrials.gov identifier: NCT03298061. Trial registration: ClinicalTrials.gov identifier: NCT03557060. Trial registration: ClinicalTrials.gov identifier: NCT03010436. Trial registration: ClinicalTrials.gov identifier: NCT02947945. Trial registration: ClinicalTrials.gov identifier: NCT01671956. Trial registration: ClinicalTrials.gov identifier: NCT02226146. Trial registration: ClinicalTrials.gov identifier: NCT03436797. Trial registration: ClinicalTrials.gov identifier: NCT03496571. Trial registration: ClinicalTrials.gov identifier: NCT03379311. Trial registration: ClinicalTrials.gov identifier: NCT01920893. Trial registration: ClinicalTrials.gov identifier: NCT03359356. Trial registration: ClinicalTrials.gov identifier: NCT03749135. Trial registration: ClinicalTrials.gov identifier: NCT03678545. Trial registration: ClinicalTrials.gov identifier: NCT02379052. Trial registration: ClinicalTrials.gov identifier: NCT00785668. Trial registration: ClinicalTrials.gov identifier: NCT01902290. Trial registration: ClinicalTrials.gov identifier: NCT03403036. Trial registration: ClinicalTrials.gov identifier: NCT02429882. Trial registration: ClinicalTrials.gov identifier: NCT02512900. Trial registration: ClinicalTrials.gov identifier: NCT02807103. Trial registration: ClinicalTrials.gov identifier: NCT03164473.