S1PR5-IN-1 (Compound 7a) is a selective S1PR5 inhibitor capable of crossing the blood-brain barrier, with an IC50 of 85.4 nM. It exhibits exceptional binding affinity to S1PR5, with Kd values of 2.2 nM for recombinant human S1PR5 cell membranes, 4.6 nM for C57BL/6 mouse brains, and 27.6 nM for human cerebral cortex. S1PR5-IN-1 is applicable in researching neurodegenerative diseases such as multiple sclerosis.