15(S)-15-methyl Prostaglandin D2 (15(S)-15-methyl PGD2) is a metabolically stable synthetic analog of PGD2 . In contrast to PGD2, 15(S)-15-methyl PGD2 induces vasoconstriction and increases systemic blood pressure with much reduced inhibitory activity on ADP-induced platelet aggregation. It also exhibits strong antifertility activity in hamsters (200-fold more potent than PGD2).