Tanaproget ( INN; developmental code names NSP-989, WAY-166989) is an investigational nonsteroidal progestin. It is a high  affinity, high efficacy, and very selective agonist of the progesterone receptor (PR). Due to its much more selective binding profile relative to most conventional, steroidal progestins, tanaproget may prove to produce fewer  side effects in comparison. As of December 2010,  it is in  phase II clinical trials in the process of being developed for clinical use as a contraceptive by Ligand Pharmaceuticals.  
analog of tanaproget, 4-fluoropropyltanaproget (, has been developed as a 18F) radiotracer for imaging of the PR in positron emission tomography. 
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References [ edit ]
^ a b c Zhang Z, Olland AM, Zhu Y, et al. (August 2005). "Molecular and pharmacological properties of a potent and selective novel nonsteroidal progesterone receptor agonist tanaproget". J. Biol. Chem. 280 (31): 28468–75. doi: 10.1074/jbc.M504144200. PMID 15937332.
^ Bapst JL, Ermer JC, Ferron GM, Foss D, Orczyk GP (November 2006). "Pharmacokinetics and safety of tanaproget, a nonsteroidal progesterone receptor agonist, in healthy women". Contraception. 74 (5): 414–8. doi: 10.1016/j.contraception.2006.06.004. PMID 17046384.
^ Bayés M, Rabasseda X, Prous JR (September 2005). "Gateways to clinical trials". Methods Find Exp Clin Pharmacol. 27 (7): 505–22. PMID 16258596.
^ Lee JH, Zhou HB, Dence CS, Carlson KE, Welch MJ, Katzenellenbogen JA (June 2010). "Development of [F-18]fluorine-substituted Tanaproget as a progesterone receptor imaging agent for positron emission tomography". Bioconjug. Chem. 21 (6): 1096–104. doi: 10.1021/bc1001054. PMID 20496889.