Biologic therapy in rare eosinophil-associated disorders: remaining questions and translational research opportunities
Authors: Khoury Paneez , Roufosse Florence , Kuang Fei Li , Ackerman Steven J , Akuthota Praveen , Bochner Bruce S , Johansson Mats W , Mathur Sameer K , Ogbogu Princess U , Spencer Lisa A , Wechsler Michael E , Zimmermann Nives , Klion Amy D ,   International Eosinophil Society Clinical Research Interest Group, Ackerman Steven , Akuthota Praveen , Amber Kyle , Baatjes Adrian , Bahadori Lila , Baudy Peter , Baylis Lee , Bochner Bruce , Brister Danica , Brunet Lisa , Carpentier Caroline , Carstens Donna , Catherine Julien , Chevalier Kevin , Chhiba Krishan , Cook-Mills Joan , Coussement Gauthier , Denburg Judah , Diab Nermin , Drake Matthew , Friend William , Fryer Allison , Fulkerson Patricia , Furuta Glenn , Gauvreau Gail , Gleich Gerald , Goddard Jamie , Groh Matthieu , Hogan Nicholas , Jacobsen Elizabeth , Johansson Mats , Kahn Jean-Emmanuel , Karimi Sina , Khoury Paneez , Kim Tae-Bum , Kita Hirohito , Klion Amy , Kovalszki Anna , Li Kuang Fei , Kwiatek Justin , Lee Ji-Hyang , Leiferman Kristin , Levi-Schaffer Francesca , Llanos Jean-Pierre , Maric Irina , Masterson Joanne , Mathur Sameer , Melhorn James , Menzies-Gow Andrew , Minnicozzi Mike , Mok Alexander , Montizaan Daphne , Munitz Ariel , Nader Luiza , Ogbogu Princess , Oladipo Olusola , O'Riordan Thomas , Orlandini Keith , Prussin Calman , Rothenberg Marc , Roufosse Florence , Shi Guo-Ping , Shiraishi Yoshiki , Simon Dagmar , Simon Hans-Uwe , Smith Steven , Spencer Lisa , Ueki Shigeharu , Wechsler Michael , Weller Peter , Wright Benjamin , Zimmermann Nives 
Published: March 2024

Abstract
Rare eosinophil-associated disorders (EADs), including hypereosinophilic syndrome, eosinophilic granulomatosis with polyangiitis, and eosinophilic gastrointestinal disorders, are a heterogeneous group of conditions characterized by blood and/or tissue hypereosinophilia and eosinophil-related clinical manifestations. Although the recent availability of biologic therapies that directly and indirectly target eosinophils has the potential to dramatically improve treatment options for all EADs, clinical trials addressing their safety and efficacy in rare EADs have been relatively few. Consequently, patient access to therapy is limited for many biologics, and the establishment of evidence-based treatment guidelines has been extremely difficult. In this regard, multicenter retrospective collaborative studies focusing on disease manifestations and treatment responses in rare EADs have provided invaluable data for physicians managing patients with these conditions and helped identify important questions for future translational research. During the Clinical Pre-Meeting Workshop held in association with the July 2023 biennial meeting of the International Eosinophil Society in Hamilton, Ontario, Canada, the successes and limitations of pivotal multicenter retrospective studies in EADs were summarized and unmet needs regarding the establishment of guidelines for use of biologics in rare EADs were discussed. Key topics of interest included (1) clinical outcome measures, (2) minimally invasive biomarkers of disease activity, (3) predictors of response to biologic agents, and (4) long-term safety of eosinophil depletion. Herein, we report a summary of these discussions, presenting a state-of-the-art overview of data currently available for each of these topics, the limitations of the data, and avenues for future data generation through implementation of multidisciplinary and multicenter studies.