CSF1R-IN-15 (compound 23) is an inhibitor targeting CSF1R. The colony-stimulating factor-1 receptor (CSF1R) is a tyrosine kinase embedded in the cell membrane of macrophages. The receptor is activated by colony-stimulating factor-1 (CSF-1) and interleukin-34, and signaling via CSF1R is crucial for the differentiation, proliferation, and survival of macrophages.