Efficacy of anti-interleukin 5 therapy in hypereosinophilic syndrome: An updated systematic review and meta-analysis

Background: Hypereosinophilic syndromes (HES) are marked by persistent eosinophilia, absence of a primary cause, and evidence of eosinophil-mediated organ damage. HES presents a spectrum of clinical manifestations, with prognosis and treatment varying based on the subtype, including myeloid/lymphoid neoplasms and chronic eosinophilic leukemia, not otherwise specified. The primary treatment goal is to reduce eosinophil levels to prevent organ damage, typically by using glucocorticoids and immunosuppressive agents. However, these treatments often have limited efficacy and considerable adverse effects. Objective: Given the central role of interleukin (IL) 5 in eosinophil development and survival, this study aimed to assess the efficacy and safety of anti‐IL-5 therapies in patients with HES. Methods: A systematic literature search was conducted on two data bases. The primary outcome was the reduction in absolute eosinophil count, and secondary outcomes included the incidence of flares and adverse events. Data Analysis was conducted, and forest plots were made for each outcome. Results: Four trials were included in the analysis. Ninety-five percent of the patients in the anti‐IL-5 group showed a reduction in the absolute eosinophil count compared with 41% in the placebo group (risk ratio [RR] 2.32 [95% confidence interval {CI}, 1.67‐3.22]; p = <0.00001; tau statistic (I 2 ) = 0%). Anti‐IL-5 therapy was associated with a lower incidence of disease flares, with 15% of the patients in the anti‐IL-5 group who experienced flares compared with 30% in the placebo group (RR 0.50 [95% CI, 0.31‐0.86]; p = 0.01; I 2 = 0%). The incidence of adverse events was similar between the two groups (RR 0.99 [95% CI, 0.91‐1.07]; p = 0.81; I 2 = 0%). Conclusion: Anti‐IL-5 therapies are effective in reducing eosinophil count and preventing disease flares in patients with HES.