W146
(R)-3-Amino-(3-hexylphenylamino)-4-oxobutylphosphonic acid (TFA salt)
Compound 2a is a selective antagonist for human S1P1 (hS1P1) receptor activation by the physiological agonist S1P. (a) Structures of 2a and 2b. (b) Shift in EC50 for S1P activation of hS1P1 receptor by 2a and 2b. We tested CHO cell membranes expressing stably transfected hS1P1 receptors for antagonism in a GTP-gS binding assay. Activation of hS1P1 receptors by 1 alone (closed squares) or in the presence of 10 mM 2a (inverted triangles) and 2b (circles) is expressed normalized to percentage GTP-gS binding induced at maximal S1P concentration. The EC50 value was 0.8 nM for 1 alone; it was 398 nM and 50 nM in the presence of 2a and 2b, respectively. (c) We derived Ki values for S1P activation of the hS1P1 receptor from antagonist competition curves; they were 77 nM for 2a (inverted triangles) and 4.63 mM for 2b (circles).
