Additional studies on pregnancy termination and inhibition of the monkey corpus luteum with 5-oxa-17-phenyl-18,19,20-trinor-PGF1α methyl ester and structurally related prostaglandins

Oral administration of 5-oxa-17-phenyl-18,19,20-trinor-PGF_1α methyl ester (PGF-analog) resulted in a consistent and dose-dependent inhibition of corpus luteum progesterone production in nonpregnant rhesus monkeys concomitantly treated with human chorionic gonadotropin. Similarly, vaginal suppositories containing PGF-analog also inhibited the monkey corpus luteum. Side effects by the oral route of administration were minimal, whereas side effects of following vaginal treatment with PGF-analog were higher. Five prostaglandings with structural similarity to PGF-analog were studied for their ability to inhibit the monkey corpus luteum, but none showed an advantage over the parent molecule. PGF-analog did not synergize with 9-deoxo-16,16-dimethyl-9-methylene-PGE₂ for the inhibition of the monkey corpus luteum, nor did it synergize with (15S)-15-methyl-PGF₂α methyl ester for the interruption of early pregnancy in the monkey. 9-Deoxo-9-methylene-5-oxa-17-phenyl-18,19,20-trinor-PGE₁ methyl ester did not terminate early gestation in the monkey at doses of 8 or 24 mg.