15(R)-17-phenyl trinor Prostaglandin F2α isopropyl ester

15(R)-17-phenyl trinor Prostaglandin F2α isopropyl ester (15(R)-17-phenyl trinor PGF2α isopropyl ester) is the latanoprost-related isomer containing both a double bond at 13,14 and an inverted (β) hydroxyl group at C-15. Similar to 15(S)-latanoprost, 15(R)-17-phenyl trinor PGF2α isopropyl ester is a potential impurity in most commercial preparations of the latanoprost bulk drug product. The IC50 values for the free acid forms of 15(S)-17-phenyl trinor PGF2α and 15(R)-17-phenyl trinor PGF2α were determined to be 0.71 nM and 30 nM, respectively, in a FP receptor binding assay using the cat iris sphincter muscle. A 3 µg dose of 15(R)-17-phenyl trinor PGF2α caused a 1.9 mmHg reduction of IOP in normotensive cynomolgus monkeys.