Pharmacological activities of the progestin STS 557

This paper reports on pharmacological properties of 17 alpha-cyano-methyl-17 beta-hydroxy-estra-4, 9-dien-3-one (STS 557), which were obtained from basic screening investigations. At high doses (100 mg/kg i.p.) STS 557 was sedatively active on the CNS, but did not show any narcotic or anticonvulsant activities. A hypothermic effect of STS 557 was found at non-sedative i.p. or oral doses in mice and rats. This was also shown for the standard levonorgestrel, doubtlessly to a lesser extent. The cardiovascular system as well as the renal excretion of urine and electrolytes were unaffected by the test compound. STS 557 was found to stimulate the spontaneous motility of the isolated rat uterus dose-dependently; an antiprogesteronic activity seems to be unlikely. STS 557 did not show any glucocorticoid or antiexudative properties. At oral dose levels of 10 and 50 mg/kg (X 4 days), STS 557 and levonorgestrel caused similar changes in the serum lipids of normolipidemic and hyperlipidemic rats. The concentration of total cholesterol was decreased, that of the FFA was increased. The triglycerides were lowered only in hyperlipidemic animals. All the pharmacological effects of STS 557 appeared at high doses, much higher than te proposed therapeutic ones.