Ralinepag (APD811) is a potent, orally bioavailable agonist of non-prostanoid prostacyclin (IP) receptor, with EC50s of 8.5 nM, 530 nM and 850 nM for human and rat IP receptor and human DP1 receptor, respectively.

DP1 (human):850 nM(EC50), IP (human):8.5 nM(EC50), IP (rat):530 nM(EC50)

Ralinepag (5c) has potent receptor binding affinity at prostaglandin receptor, with Kis of 1.2 nM, 3 nM, 76 nM, and 256 nM for monkey, human, rat, and dog IP receptor (ligand, [3H]-iloprost), and 2.6 μM, 9.6 μM, 610 nM, 143 nM, and 678 nM for human DP1, EP1, EP2, EP3v6 and EP4 receptors (ligand, [3H]-PGE2), respectively. Moreover, Ralinepag shows no effect on cytochrome P450 enzymes (IC50 > 50 μM for CYPs 1A2, 2D6, 3A4 2C8, 2C9, and 2C19) or hERG channel functional activity in a patch clamp assay (IC50 > 30 μM). Ralinepag also inhibits the ADP-induced human platelet aggregation, with an IC50 of 38 nM[1].

Ralinepag (30 mg/kg, orally) significantly mitigates the increase in pulmonary arterial pressure and the thickening of pulmonary vessel walls in rats induced by monocrotaline (MCT)[1].