The biological profile of a new synthetic progestagen--GR2-1159-(17-acetoxy-6,11 beta-dichloro-19-nor-4,6-pregnadiene-3,20-dione)

The biological activity of a new progestagen-GR2/1159-is reported. When tested by the oral, subcutaneous and intrauterine routes in the rabbit GR2/1159 had respectively 162, 191 and 226 times the activity of progesterone. High progestational activity has also been confirmed in a maintenance of pregnancy test in the rat and in the mouse deciduoma test. Compared with progesterone (= 1) GR2/1159 possessed anti-estrogenic activity of 73 subcutaneously in mice and of 114 and 79 by the subcutaneous and oral routes in rats. In the anti-gonadotrophic test GR2/1159 was 93 times as active as progesterone when administered subcutaneously to rats. GR2/1159 also showed weak adrenocorticoid activity in the rat. GR2/1159 was without estrogenic, androgenic, anabolic or anti-androgenic activity in rats and mice. Its biological profile in animals was thought to make it well suited for use as a continuous low-dose contraceptive preparation, but preliminary clinical investigation has not substantiated this.