W140 is the inactive enantiomer of the sphingosine-1-phosphate receptor 1 (S1P1) antagonist W146 .1 It only weakly binds to S1P1 (Ki = 4.6 μM for the human receptor). W140 has been used as a negative control in vitro and in vivo in the study of S1P1 signaling.1,2
