Dienogest (STS 557) is an orally-active, semisynthetic, fourth generation, nonethinylated progestogen with antiproliferative, antiandrogenic, anti-inflammatory and antiangiogenic activities that is used in hormone therapy and as a female contraceptive.

Concurrent administration of Dienogest (0.1 mg/kg/day) and Ethinyl estradiol (0.3 mg/kg/day) can inhibit the effects induced by Ethinyl estradiol without affecting the efficacy on uterine endometrial implants. Additionally, Dienogest administered orally at doses ranging from 0.1 to 1 mg/kg/day reduces the volume of endometrial implants in rats, achieving a reduction similar to that of Danazol at 100 mg/kg/day, also administered orally.

In cultured endometriotic stromal cells, Dienogest (0.1-1 μM) significantly inhibits BrdU incorporation into DNA after 24 and 48 hours, also notably increases the number of cells in the G0/G1 phase while decreasing the cells in the S and G2/M phases. Dienogest activates progesterone receptors (EC50: 3.4/10.5 nM) and antagonizes androgen receptors (EC50: 420.6/775.0 nM) without exhibiting antagonism towards GR and MR at 3 nM. In human endometrial stromal cells, the combined use of Dienogest and estradiol (estrogen) dose-dependently increases prolactin mRNA and protein levels.

Kinase inhibition assays: For the VEGFR2, Flk1 and FGFR1 kinase assays, BMS-582664 is dissolved in DMSO and diluted with water/10% DMSO to a final DMSO concentration of 2%. The kinase reactions consists of 8 ng of enzymes with GST tag, 75 μg/mL substrate, 1 μM ATP, and 0.04 μCi [γ-33P]ATP in 50 μL total reaction volume (kinase buffer:? 20 mM Tris, pH 7.0, 25 μg/mL BSA, 1.5 mM MnCl2, 0.5 mM dithiothreitol). In all cases, the reactions are incubated for 60 min at 27℃ and terminated with the addition of cold trichloroacetic acid (TCA) to a final concentration of 15%. The percent inhibition from the kinase assays is determined by nonlinear regression analyses, and data are reported as the inhibitory concentration required to achieve 50% inhibition relative to control reactions (IC50).