Repurposing indacaterol as a novel NETs inhibitor for the treatment of colorectal tumor metastasis.

Metastasis remains the leading cause of cancer-related mortality, driven by multifaceted interactions within the tumor microenvironment (TME). Recently, Neutrophil Extracellular Traps (NETs) have emerged as critical facilitators of metastatic progression. This study aimed to systematically screen FDA-approved drugs to identify novel NET inhibitors and evaluate the potential of indacaterol (IND) as an anti-metastatic agent. The screening identified IND as a potent inhibitor of NETosis (IC50 = 6.567 μM), significantly suppressing extracellular DNA release and Citrullinated Histone H3 expression in a dose-dependent manner. In vitro investigations revealed that IND exerts a dual therapeutic effect: directly inhibiting tumor cell proliferation and migration, and indirectly restoring anti-tumor immunity by dismantling the NET barrier, evidenced by revitalized CD8 + T cell activation (CD25 + ) and IFN-γ secretion. Additionally, IND promoted macrophage polarization toward an M2 phenotype, facilitating the phagocytic clearance of NETs. In vivo, IND treatment markedly reduced circulating NET levels and significantly suppressed metastatic colonization in the liver and spleen. This study provides the first systematic evidence positioning Indacaterol as a novel and potent NETs inhibitor. By effectively blocking NET formation and remodeling the immune microenvironment, IND demonstrates significant anti-metastatic potential. Leveraging its established pharmacological and safety profile, Indacaterol represents a promising candidate for rapid clinical repurposing to target NET-mediated metastasis, particularly in malignancies characterized by systemic inflammation.