Tanaproget is a novel nonsteroidal progesterone receptor agonist which can bind to the PR from various species with a higher relative affinity than reference steroidal progestins (IC50: 0.1 nM),

In T47D cells, TNPR induces alkaline phosphatase activity with an EC(50) value of 0.1 nm, comparable with potent steroidal progestins such as medroxyprogesterone acetate (MPA) and trimegestone (TMG), albeit with a reduced efficacy ( approximately 60%). In a mammalian two-hybrid assay to measure PR agonist-induced interaction between steroid receptor co-activator-1 and PR, TNPR showed similar potency (EC(50) value of 0.02 nm) and efficacy to MPA and TMG [1].

TNPR effectively down-regulated MMP expression in vitro and induced a significant reduction of lesions in mice with disease established by tissues from endometriosis patients. The maximum concentration (C(max)) of tanaproget occurred approximately 2 to 3 h after administration. The elimination half-life (t(1/2)) ranged from 12 to 30 h, and the oral clearance was approximately 70 L/h. The pharmacokinetics of tanaproget was not noticeably altered with a high-fat meal [2][3].