Nextstellis

Combined oral contraceptives (COCs) prevent pregnancy primarily by suppressing ovulation. Estetrol (E4) is a naturally occurring estrogen produced by the human fetal liver. It is only produced during human pregnancy and reaches the maternal circulation through the placenta. The E4 in Nextstellis is synthesised from a plant source. Estetrol displays a high selectivity for estrogen receptors (ERs) and binds to both estrogen receptor alpha (ERα) and estrogen receptor beta (ERβ), with a 4 to 6 times higher affinity for ERα compared to ERβ. Estrogen agonist activity by E4 was demonstrated in various cell based assays in vitro and animal models in vivo. Estetrol differs from ethinylestradiol by the lack of an ethinyl group in the 17-alpha position. In humans, E4 is an end product of steroid metabolism and is not reconverted to estriol, estradiol or estrone.The progestin drospirenone possesses antigonadotropic, antiandrogenic and mild antimineralocorticoid properties and has no estrogenic, glucocorticoid or antiglucocorticoid activity. These properties are pharmacologically similar to the natural hormone progesterone.