Preliminary Effects of Benralizumab in an AML Cell Model with Promyelocytic Features Expressing IL-5R: An Exploratory Proof-of-Concept Study

<b>Background/Objectives:</b> Acute myeloid leukemia (AML) comprises a heterogeneous group of diseases, with some subtypes displaying promyelocytic features and altered differentiation programs. Aberrant cytokine receptor signaling has been implicated in leukemogenesis, and IL-5Rα has recently emerged as a potential marker in selected AML subsets, including promyelocytic variants. Benralizumab is a monoclonal antibody directed against the alpha chain of the interleukin-5 receptor (CD125), which blocks IL-5Rα-mediated signaling. This proof-of-concept study aimed to explore the effects of the anti-IL-5Rα monoclonal antibody Benralizumab in an in vitro AML cell model with promyelocytic characteristics. <b>Methods:</b> Public transcriptomic datasets were analyzed to evaluate IL-5Rα expression in AML subtypes. HL-60 cells, an AML cell line expressing IL-5Rα, were treated with Benralizumab and analyzed for cell cycle distribution and modulation of key signaling and apoptotic pathways by flow cytometry and Western blotting. <b>Results:</b> IL-5Rα was highly expressed in AML, particularly in M2 and M3 subtypes. Benralizumab treatment reduced STAT3 expression, activated ERK and NF-κB signaling, induced p21 and p27 expression, altered cell cycle distribution, and induced caspase-8 cleavage, suggesting activation of extrinsic apoptotic signaling. <b>Conclusions:</b> These findings provide preliminary proof-of-concept evidence that IL-5Rα targeting by Benralizumab may directly affect cell survival and cell cycle regulation in AML cells with promyelocytic characteristics. When interpreted together with the in silico analyses performed on AML patient datasets, these results support the rationale for future validation in APL-oriented models carrying the PML::RARα fusion, the disease-defining oncogenic driver generated by the t(15;17) translocation that blocks myeloid differentiation. However, the in silico and in vitro datasets were not formally integrated at the patient level, and these functional results should be considered exploratory.