Histamine release

KP136 (0.01 μg/mL) inhibits this histamine release and degranulation in a dose-dependent manner, confirming that it is an inhibitor of mast cell activation. The IC ₅₀ is 76.1 μg/mL for histamine release and 63 ug/mL for degranulation.

C4C at 0.2 mg/kg produces an equipotent effect to 1 mg/kg KP136 (KP-136) or 5 mg/kg DSCG. However, C4C is less effective by the oral route because it only produces a maximum inhibition of about 35% even at the high dose of 100 mg/kg, whereas KP136 shows an overt inhibitory effect of about 66% at the oral dose of 2 mg/kg. On the other hand, KP136 (1 mg/kg, i.v.) also remarkably inhibits 5-h homologous PCA, having an activity similar to that of C4C.