PGD2 is one of the five primary enzymatic prostaglandins derived directly from PGH2. Many of the biological effects of PGD2 are transduced in vivo by a classical 7-transmembrane GPCR, the DP1 receptor.{3128} However, a second receptor, the chemokine-related CRTH2 receptor, also binds PGD2.{10058,10722} This new receptor was recently identified on human eosinophils, where it binds selectively the PGD2 metabolite 13,14-dihydro-15-keto PGD2.{9769} 11-deoxy-11-methylene-15-keto PGD2 was prepared as a more chemically stable ligand for this receptor. There are no published studies of the pharmacological properties of 11-deoxy-11-methylene-15-keto PGD2.