BMY 45778 is a partial agonist of prostacyclin receptor [1].

Prostacyclin receptor (IP1) is a G-protein coupled receptor for prostacyclin. Prostacyclin inhibits platelet aggregation and elicits a potent vasodilation through binding to this receptor.

BMY 45778 is a partial agonist of prostacyclin receptor. BMY 45778 inhibited platelet aggregation with IC50 values of 35 nM, 136 nM and 1.3 μM in human, rabbit and rat, respectively. In human platelet membrane, BMY 45778 activated adenylyl cyclase with ED50 value of 6-10 nM and stimulated GTPase. Also, BMY 45778 completely inhibited the binding of Iloprost to platelet membranes with IC50 value of 7 nM. BMY 45778 inhibited iloprost-stimulated GTPase, which suggested that BMY 45778 is a partial agonist of prostacyclin receptor. In whole platelets, BMY 45778 increased cAMP levels and activated cAMP-dependent protein kinase [1]. BMY 45778 (1-10 μM) inhibited rat neutrophil aggregation induced by N-formyl-methionyl-leucylphenylalanine with IC50 value of 20 nM and inhibited the spontaneous activity of rat colon by 10-20%. Also, BMY 45778(10 μM) inhibited the inhibitory effect of cicaprost on rat colon [2].

References:
[1].  Seiler SM, Brassard CL, Federici ME, et al. [3-[4-(4,5-Diphenyl-2-oxazolyl)-5-oxazolyl]phenoxy]acetic acid (BMY 45778) is a potent non-prostanoid prostacyclin partial agonist: effects on platelet aggregation, adenylyl cyclase, cAMP levels, protein kinase, and iloprost binding. Prostaglandins, 1997, 53(1): 21-35.
[2].  Wise H, Qian YM, Jones RL. A study of prostacyclin mimetics distinguishes neuronal from neutrophil IP receptors. Eur J Pharmacol, 1995, 278(3): 265-269.