Mespirenone
Mespirenone (INN) (developmental code name ZK-94679), also known as Δ1-15β,16β-methylenespironolactone, is a steroidal antimineralocorticoid of the spirolactone group related to spironolactone that was never marketed.[1][2] Animal research found that it was 3.3-fold more potent as an antimineralocorticoid relative to spironolactone.[3] In addition to its antimineralocorticoid properties, mespirenone is also a progestogen, antigonadotropin, and antiandrogen.[2][4] It is 2- to 3-fold as potent as spironolactone as a progestogen and antigonadotropin but its antiandrogenic activity is markedly reduced and weak (though still of significance) in comparison.[4][5] Mespirenone is also a potent and specific enzyme inhibitor of 18-hydroxylase and thus of mineralocorticoid biosynthesis.