Real-world outcomes after anti-IL-5/anti-IL-5Rα treatment for hypereosinophilic syndrome: Systematic literature review.

Background: Anti-IL-5/anti-IL-5 receptor alpha (anti-IL-5/anti-IL-5Rα) treatments have potential to improve outcomes in hypereosinophilic syndrome (HES), as demonstrated in clinical trials. Objective: We sought to understand the real-world outcomes of anti-IL-5/anti-IL-5Rα treatments in patients with HES. Methods: This systematic literature review searched English-language articles (November 4, 2015, to October 31, 2023) and conference abstracts (January 1, 2021, to October 31, 2023) from MEDLINE/Embase and select conferences for publications containing outcomes for patients with HES receiving anti-IL-5 (mepolizumab [approved], reslizumab) or anti-IL-5Rα (benralizumab) treatment in the real world. Meta-analyses and clinical trials were excluded. Outcomes included treatment response, blood eosinophil (bEOS) counts, and oral corticosteroid (OCS) receipt. No formal bias assessment was conducted. Results: Five cohort studies (192 participants) and 55 case reports (70 participants) were identified. In cohort studies, median age was 44.0 to 61.8 years; 33.3% to 62.9% were female, and 45.5% to 100% had idiopathic HES. Mean (standard deviation) age in case reports (n = 68/70) was 38.5 (23.7) years; 40.0% (n = 28/70) were female, and 67.2% (n = 39/58) had idiopathic HES. Across 4 cohort studies, most patients had reduced or no HES flares after mepolizumab or benralizumab. In patients from case reports, 13 had HES flares (mepolizumab, n = 12/54; benralizumab, n = 1/13) after anti-IL-5/anti-IL-5Rα initiation. Mean bEOS counts were reduced by 53.0% to 100% across 3 cohort studies and by 95.0% in case reports. Of those receiving benralizumab or mepolizumab, OCS dose was reduced in 49.0% to 100% of patients from cohort studies, and by ≥50% in 29 of 70 patients from case reports. Conclusion: Real-world anti-IL-5/anti-IL-5Rα therapy in HES is associated with fewer flares as well as reductions in bEOS counts and OCS dose, although confirmatory studies in larger populations are needed.