Nomegestrol acetate: steroid receptor transactivation profile in Chinese hamster ovary cells and ovulation inhibition in rat and monkey

BackgroundActivity of nomegestrol acetate (NOMAC), levonorgestrel (LNG), drospirenone (DRSP), dienogest (DNG) and progesterone on human steroid receptor transactivation was investigated. Ovulation inhibition by NOMAC, LNG and progesterone was tested.Study DesignThe progestogen receptor profile was determined in Chinese hamster ovary cells transfected with human progesterone B (PRB), androgen, estrogen (ERα and ERβ), glucocorticoid (GR) and mineralocorticoid (MR) receptors, respectively. Ovulation inhibition was tested in rats and monkeys.ResultsAgonistic potency rankings for PRB were LNG=NOMAC≫progesterone≫DRSP>DNG. No antagonistic activity at PRB was observed. Only LNG had androgenic activity. Antiandrogenic potency rankings were LNG≫NOMAC>progesterone>DNG>DRSP. All agents were devoid of activity at ERα, ERβ and GR. Only progesterone, DRSP and LNG had anti-MR activity. The NOMAC dose inhibiting ovulation at 50% ranged from 0.14 mg/kg (monkey) to 1.25 to 5.0 mg/kg (rat).ConclusionNomegestrol acetate is a selective progestogen and a potent inhibitor of ovulation in the rat and monkey.