Asapiprant (S-555739) is a potent and selective DP1 receptor antagonist (Ki: 0.44 nM). It exhibited high affinity and selectivity for the DP1 receptor.

DP1 receptor:0.44 nM (Ki)

Asapiprant 在人类血小板中，对由 PGD2 引起的 cAMP 升高具有强烈的抑制作用，其半数最大抑制浓度（IC50）值为 16 nM。在豚鼠、大鼠和绵羊体内，由 PGD2 诱导的 cAMP 升高也观察到 asapiprant 的强烈抑制作用，其 IC50 值（nM）分别为 61、74 和 15。

经鼻腔挑战0.5%的PGD2后，对敏感豚鼠产生了从5分钟到60分钟的鼻阻力（sRaw）迅速增加现象。口服asapiprant以1和3mg/kg的剂量显著抑制了鼻阻力的增加，分别达到82%和92%。相比之下，在30mg/kg的剂量下，S-5751对PGD2引起的鼻阻力在豚鼠中只产生了76%的部分抑制效果，这与3mg/kg剂量的asapiprant的抑制效果相比较为劣势。

The functional antagonist activity of asapiprant on the DP1 receptor was evaluated by examining PGD2-induced elevation of cyclic adenosine monophosphate (cAMP) in platelet-rich plasma derived from venous blood (humans, guinea pigs, and sheep), and in rat DP1-transfected cells stimulated with PGD2, as described elsewhere. The functional antagonist activity of asapiprant on the DP2 receptor was evaluated by examining PGD2-induced shape change of peripheral eosinophils derived from humans and guinea pigs, as reported previously.

After the oral administration of asapiprant or S-5751 to rats, guinea pigs, dogs, and sheep at 10 mg/kg in suspension with 0.5% methylcellulose solution, the plasma concentrations of the drugs were measured by liquid chromatography/tandem mass spectrometry or high-performance liquid chromatography.