Discovery of 13-oxa prostaglandin analogs as antiglaucoma agents: Synthesis and biological activity

FP-Class prostaglandin analogs have demonstrated utility for the treatment of glaucoma and ocular hypertension. A series of novel FP prostaglandin analogs was designed to optimize topical ocular activity and reduce ocular side-effects by replacing 13-carbon with oxygen. A facile synthesis was successfully developed for synthesis of the 13-oxa prostaglandins from the commercially available Corey aldehyde benzoate. Among the compounds synthesized, AL-16082 was the most potent prostaglandin FP agonist in vitro. In a prostaglandin FP receptor-linked second-messenger assay, phosphoinositide (PI) turnover, it exhibited a potency value (EC₅₀) of 1.9 nM (78% max. response relative to fluprostenol). The isopropyl ester of AL-16082, compound AL-16049, significantly lowered intraocular pressure (IOP) in the ocular hypertensive monkey eyes by 30%. In the study of acute ocular irritation response in New Zealand albino rabbits, AL-16049 produced lower incidence of hyperemia, swelling, and discharge than PGF_2α (1 μg), and a similar incidence of hyperemia, swelling, and discharge to latanoprost (1.8 μg). AL-16049 also produced no signs of ocular irritation or discomfort in the cat at the doses evaluated.