Purpose <p>Colony-stimulating factor 1 receptor (CSF1R) signaling plays a pivotal role in neuroinflammation, driving microglia proliferation and activation. CSF1R is considered a hallmark of inflammation in many neurodegenerative diseases, such as Alzheimer’s disease (AD) and Parkinson’s disease (PD). Our study aims to evaluate the potential value of 5-cyano-N-(4-(4-(2-([¹⁸F]fluoro)ethyl)piperazin-1-yl)-2-(piperidin-1-yl)phenyl)furan-2-carboxamide ([¹⁸F]JNJ-CSF1R-1) as a positron emission tomography (PET) ligand targeting CSF1R in preclinical models of neuroinflammation.</p> Procedures <p>A cell-based MSD assay was used to measure the IC₅₀ of 5-cyano-N-(4-(4-(2-(fluoro)ethyl)piperazin-1-yl)-2-(piperidin-1-yl)phenyl)furan-2-carboxamide (JNJ-CSF1R-1). JNJ-CSF1R-1 was radiolabeled with fluorine-18. PET imaging was used to evaluate brain uptake, and target engagement of [¹⁸F]JNJ-CSF1R-1 in two neuroinflammation mouse models, including systemic lipopolysaccharide (LPS) and <i>App</i>^SAA knock in (KI). CSF1R protein levels in brain tissue were determined by western blot and ELISA assays. [¹⁸F]JNJ-CSF1R-1 brain uptake was also measured in a non-human primate (NHP) PET study.</p> Results <p>JNJ-CSF1R-1 is a 12&#xa0;nM (IC₅₀) inhibitor of CSF1R. ​[¹⁸F]JNJ-CSF1R-1 demonstrated significantly higher brain uptake in both LPS and AD mouse models as measured by the area under the time activity curves (AUC) compared to control animals. In the <i>App</i>^SAA KI model, CSF1R levels increased near amyloid plaques as detected by IHC. ​[¹⁸F]JNJ-CSF1R-1 PET imaging signal showed a good correlation with CSF1R expression levels measured by western blot and ELISA. In an NHP study, ​[¹⁸F]JNJ-CSF1R-1 readily entered the brain and demonstrated reversible kinetics.</p> Conclusion <p>​[¹⁸F]JNJ-CSF1R-1 is a potent and promising CSF1R PET tracer with translational potential for measuring microglia-based neuroinflammatory processes and for tracking the impact of anti-inflammatory therapies.</p>