20-ethyl Prostaglandin E2 (20-ethyl PGE2) is an analog of PGE2 in which the ω-chain has been extended by the addition of two methylene carbon atoms. The only well studied prostaglandin analog with this structural feature is unoprostone, an F-series prostaglandin that is clinically approved as a glaucoma medication.¹ Unoprostone also contains lower side chain modifications (13,14-dihydro-15-keto) which severely limit its affinity for FP receptors, contributing to its lack of potency as a medication. 20-ethyl PGE2 retains the natural 15(S) allylic hydroxyl in the lower side chain, which may improve its potency relative to unoprostone. However, ligand binding assays of this analog with respect to EP or other prostanoid receptors have not been published. E-type prostaglandins have been widely reported to have inflammatory, cytoprotective, and a variety of other effects.^2,3,4