Identification of Second Gneration Prostamide Antagonists ( AGN 211334-6)

Abstract

Purpose: : The prostamides ( prostaglandin-ethanolamides ) and prostaglandin ( PG ) glyceryl esters are biosynthesized from the respective endocannabinoids anandamide and 2-arachidonyl glycerol via COX-2 . Early studies have suggested that the pharmacological profiles of prostamide Fα and PGE₂ glyceryl ester are unique and unrelated to prostanoid receptors. This has recently been supported by the identificaiton of a selective prostamide antagonist AGN 204396. Here we report the activty of second generation prostamide antagonists AGN 211334,35,and 36.

Methods: : Effects on human recombinant PG receptors were studied using a FLIPR instrument: stable co-transfection of cDNAs encoding the receptors and a chimeric G protein allowed functional activity to be assessed as a Ca²⁺ signal for all receptors. The isolated feline iris was used as a key preparation where prostanoid FP receptor and prostamide activity co-exist. Potent prostamide antagonists were designed by substituting the CH₂ at position 3 with an oxygen.

Results: : The prostamide antagonists AGN 211334,35,36 did not block the prostanoid FP or other PG-sensitive receptors at concentrations up to 30µM. Similiary, in the cat iris, AGN 211334-6 did not block the effects of PGF_2α. The effects of prostamide F_2α in the cat iris were antagonized by AGN 211334,35, and 36 ; AGN 211334 being approximately 10 fold more potent than the protypical antagonist AGN 204396. I.C.₅₀ values were AGN 211334=236nM, AGN 211335=356nM, AGN 211336=303nM, AGN 204396=2635nM

Conclusions: : The identification of second generation prostamide antagonists provides further support for the prostamide receptor hypothesis. AGN 211334,35, and 36 and provided agents sufficiently potent for studies in living animals.

Keywords: eicosanoids • receptors • iris