Session: 201. Granulocytes, Monocytes, and Macrophages: Poster I
Hematology Disease Topics & Pathways:
Research, Fundamental Science, GVHD, Diseases, Immune Disorders, Immunology, Biological Processes, Study Population, Human, Animal model
Methods: The mechanism of action of axatilimab was characterized using in vitro assays with primary human monocytes and macrophages, as well as a human CSF-1R knock-in mouse model. Expression of CSF-1R and monocyte chemoattractant protein (MCP-1) secretion (downstream of CSF-1R) were evaluated. Next, the effects of axatilimab on monocyte-to-macrophage differentiation and on monocyte-derived macrophages were assessed for inflammatory chemokines and cytokine secretion. Purified monocytes (CD14+) were cultured with macrophage CSF (M-CSF) and treated with axatilimab for 24 and 72 hours. To assess the effect of axatilimab on monocyte-derived macrophages, monocytes were differentiated into macrophages with M-CSF for 5 days and treated with axatilimab for 72 hours with appropriate controls. Supernatants from these cultures were evaluated with an 80-plex Luminex assay. To evaluate the in vivo effects of axatilimab on circulating blood monocytes, human CSF-1R knock-in mice were treated with a range of axatilimab doses (0.3–30 mg/kg) for different time intervals. A comprehensive flow cytometry panel was used to assess monocytes/macrophages in a human CSF-1R knock-in mouse model at different time points after axatilimab treatment.
Results: Axatilimab treatment of human monocytes for 72 hours resulted in impaired cell survival. Shorter treatment for 24 hours, which did not impair monocyte viability, resulted in inhibition of MCP-1 secretion, a key mediator of immune cell chemotaxis and fibrosis. In addition, axatilimab treatment led to dose-dependent inhibition of other inflammatory cytokines. Specifically, significant dose-dependent inhibition of macrophage inflammatory protein (MIP)-1α, MIP-1β, C-X-C motif chemokine ligand (CXCL)1, CXCL6, MCP-3, and MCP-2 secretion was observed in monocytes treated with axatilimab. Axatilimab treatment of monocyte-derived macrophages inhibited MIP-1α, MIP-1β, MIP-2α, interleukin 8 (IL-8), CXCL5, and MCP-1. Notably, MCP-1 and IL-8 are key regulators of tumor growth factor beta (TGF-β) and are all implicated in fibrotic disease progression. Axatilimab treatment of human CSF-1R knock-in mice led to reductions in the number of monocytes (CD45+ CD11b+) in the blood and peritoneal lavages without reducing the total leukocyte population.
Conclusions: Taken together, these data suggest that blocking CSF-1/CSF-1R signaling by axatilimab reduces proinflammatory signaling in monocytes and monocyte-derived macrophages and specifically reduces the number of monocytes and macrophages in the peripheral blood and peritoneal lavages of human CSF-1R knock-in mice. These data support the observation from clinical studies (phase 1/2 and pivotal AGAVE-201 study) that nonclassical monocytes were depleted in patients with cGVHD treated with axatilimab.
Disclosures: Bajpai: Incyte Corporation: Current Employment, Current holder of stock options in a privately-held company. Solomon: Incyte Corporation: Current Employment, Current holder of stock options in a privately-held company. Volkova: Incyte Corporation: Current Employment, Current holder of stock options in a privately-held company. Parker: Incyte Corporation: Current Employment, Current holder of stock options in a privately-held company. Kearns: Incyte Corporation: Current Employment, Current holder of stock options in a privately-held company. Cosby: Incyte Corporation: Current Employment, Current holder of stock options in a privately-held company. Kanellopoulou: Incyte Corporation: Current Employment, Current holder of stock options in a privately-held company.
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