Table 3. Binding Affinity of Representative PR Antagonists^a.

compounds	PR IC50 (nM)
Mifepristone	5.2 ± 0.53
37	1500 ± 540
40	340 ± 150
46	150 ± 110

^a4 nM [1,2,6,7-³H]progesterone was used.