A cell death screen identifies macrophage-depleting agents with therapeutic potential

Macrophages are critical regulators of inflammation and tissue homeostasis, yet aberrant macrophage activation contributes to a wide spectrum of inflammatory and malignant diseases. Therapeutic strategies that directly reduce macrophage numbers have shown promise, but macrophage survival pathways remain incompletely defined, limiting the development of targeted therapeutic strategies. Here, we establish a high-throughput screening platform to identify small molecule inhibitors that impair macrophage survival. Screening a library of more than 2,000 targeted compounds in a cell survival assay, combined with in silico and in vitro analysis of macrophage specificity, revealed the identification of three potent inhibitors: BIX-01294, GSK-J4, and Masitinib. All three compounds downregulated leukemia inhibitory factor receptor (LIFR), whose inhibition markedly reduced macrophage viability. In vivo, these inhibitors effectively depleted large peritoneal macrophages, ameliorated key symptoms of macrophage activation syndrome (MAS), and suppressed tumor growth in a syngeneic transplanted melanoma model as well as in an autochthonous lung cancer model. Together, these findings identify small molecule-mediated macrophage depletion as a promising therapeutic strategy and establish an experimental approach to uncover regulators of macrophage survival.