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.

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].