LDN-211904 is an inhibitor of EphB3 receptor tyrosine kinase. LDN-211904 enhances the inhibitory activity of EphB3 kinase by maintaining the 2-chloroaniline group and introducing a phenyl or small electron donor substituent to the 5 position of pyrazole and [1,5-a] pyridine. LDN-211904 can be used as a molecular probe to study the function and signaling pathways of EphB3 receptors, especially in the nervous system during neurodevelopment and adulthood.