PGK1 is the 9,11-diketone formed by the oxidation of PGE1 or PGD1. Whether this compound exists biologically is uncertain; it is known to be resistant to metabolism by 15-hydroxy PGDH in vitro.{1789} In an intact porcine model of balloon angioplasty restenosis, PGK1 was equivalent in activity and potency to PGE1.{6703}