SLP7111228 is a potent, selective SPHK1 inhibitor with Ki values of 0.048 μM for SPHK1 and >10 μM for SPH2K, showing a concentration-dependent reduction of sphingosine-1-phosphate (S1P) in U937 cells without affecting sphingosine levels. In vivo, it dose-dependently lowers S1P blood levels in rats.