onapristone extended release + anastrozole

Onapristone extended release (ONA-ER) is a full progesterone receptor antagonist that blocks the action of progesterone by preventing progesterone receptor-mediated DNA transcription. It inhibits both PRA and PRB monomers from dimerizing, prevents ligand-induced phosphorylation, and blocks association with coactivators, thereby suppressing PR-mediated gene expression. Anastrozole is a nonsteroidal aromatase inhibitor that selectively and competitively inhibits the aromatase enzyme, reducing estrogen biosynthesis in peripheral tissues. The combination of these two agents provides dual hormonal blockade—antiprogesterone via onapristone ER and anti-estrogen via anastrozole—which is being investigated as a nonchemotherapy alternative for hormone receptor-positive cancers such as endometrial cancer. Onapristone ER has been developed to reduce peak drug exposure and potentially lower hepatotoxicity risk compared to immediate-release formulations[3][8]. Anastrozole is approved for use in breast cancer but is also under investigation in this combination for endometrial cancer[1][4][5].

Brand names

Arimidex

Other names

onapristone extended release + anastrozoleONA-XR + ANA