The discovery of RU486 and its potent activity as an antiglucocorticoi
d and antiprogestin brought the long story on steroid hormones and ant
ihormones to its logical conclusion. Even though scattered improvement
s are still possible, the armamentarium of the steroid endocrinologist
is by now complete. Like any successful drug, RU486 has become the pr
ototype of a number of analogues which are claimed to be either more a
ctive or more dissociated. The literature (mainly patents) has been se
arched for available data on abortive activities, and some as yet unpu
blished results on RU compounds have been included. It appears that a
number of compounds are both more active than RU486 on a dose basis in
animal studies and more dissociated in relation to a possible antiglu
cocorticoid activity. In addition, hydrosoluble compounds suitable for
i.v. injection are available for possible development. In a longer te
rm perspective, it cannot be excluded that potential non-steroidal ant
iprogestins could present additional advantages over steroidal compoun
ds, in particular improved receptor specificity and/or reduced suscept
ibility to receptor mutation.