Definition

A human immunoglobulin G2 (IgG2) monoclonal antibody directed against the tyrosine kinase receptor colony stimulating factor 1 receptor (CSF1R; CSF-1R; M-CSFR; c-fms), also known as macrophage colony-stimulating factor receptor (M-CSFR) and CD115 (cluster of differentiation 115), with potential antineoplastic, anti-inflammatory, immunomodulating and anti-fibrotic activities. Upon administration, anti-CSF1R monoclonal antibody AMB-05X targets and binds to CSF1R expressed on tumor cells, monocytes and macrophages, and inhibits the binding of the CSF1R ligands and cytokines colony-stimulating factor-1 (CSF-1; CSF1) and interleukin-34 (IL-34) to CSF1R. This prevents CSF1R activation and CSF1R-mediated signaling in these cells. This blocks tumor cell proliferation and the production of inflammatory mediators by macrophages and monocytes and reduces inflammation. By blocking the recruitment to the tumor microenvironment (TME) and activity of CSF1R-dependent tumor-associated macrophages (TAMs), AMB-05X enhances T-cell infiltration and antitumor T-cell immune responses, which further inhibits the proliferation of tumor cells. TAMs play key roles in immune suppression and promoting inflammation, tumor cell proliferation and survival. In fibrosis, preventing CSF1R-mediated macrophage differentiation and fibroblast activation may prevent fibrosis. CSF1R, a cell-surface receptor overexpressed or mutated in certain tumor cell types, plays major roles in tumor cell proliferation, metastasis, inflammation, and idiopathic pulmonary fibrosis (IPF). CSF1 is overproduced in certain types of tumors.