Profile of estetrol, a promising native estrogen for oral contraception and the relief of climacteric symptoms of menopause

Introduction: Estrogens used in women's healthcare have been associated with increased risks of venous thromboembolism (VTE) and breast cancer. Estetrol (E4), an estrogen produced by the human fetal liver, has recently been approved for the first time as a new estrogenic component of a novel combined oral contraceptive (E4/drospirenone [DRSP]) for over a decade. In phase 3 studies, E4/DRSP showed good contraceptive efficacy, a predictable bleeding pattern, and a favorable safety and tolerability profile. Areas covered: This narrative review discusses E4MODIFIER LETTER PRIMEs pharmacological characteristics, mode of action, and the results of preclinical and clinical studies for contraception, as well as for menopause and oncology. Expert opinion: Extensive studies have elucidated the properties of E4 that underlie its favorable safety profile. While classical estrogens (such as estradiol) exert their actions via both activation of nuclear and membrane estrogen receptor alpha (ER alpha), E4 presents a specific profile of ER alpha activation: E4 binds and activates nuclear ER alpha but does not induce the activation of membrane ER alpha signaling pathways in specific tissues. E4 has a small effect on normal breast tissue proliferation and minimally affects hepatic parameters. This distinct profile of ER alpha activation, uncoupling nuclear and membrane activation, is unique.