This lipoxygenase-inhibiting pyrrole analogue of prostacyclin (FWpotassium salt = 463.66 g/mol; CAS 79672-88-1), also known as U60257B and 6,9- deepoxy-6,9-(phenylimino)-D6,8-prostaglandin I1, [4R-[4a(1E,3S*),5b]]- 1,4,5,6-tetrahydro-5-hydroxy-4-(3-hydroxy-1-octenyl)-1-phenylcyclopenta[ b]pyrrole-2-pentanoate, inhibits leukotriene C and D formation.1-5 Piriprost also inhibits the release of histamine and leukotrienes from isolated porcine lung cells.6 Note that both priprost and its methyl ester (U-56467) inhibit leukotriene biosynthesis: ID50 = 4.6 and 0.31 μM, respectively. Target(s): glutathione S-transferase; and 5- lipoxygenase, or arachidonate 5-lipoxygenase.