A synthetic progestin; has no estrogenic, androgenic, glucocorticoid, or anabolic effects; an agonist of progesterone receptors (EC50 = 12.3 nM); an antagonist of androgen, mineralocorticoid, and glucocorticoid receptors (IC50s = 28.6, 82.7, and 363 nM, respectively); protects against sound stress-induced abortion in mice at 1.25 mg per animal on day five of pregnancy