Pharmacology of two new very selective antiprogestagens: Org 31710 and Org 31806.

Org 31710 and Org 31806 are new antiprogestagens. These compounds were tested for their binding affinity to various steroid receptors and for their bio-activity in various animal models and the results were compared with those of RU38486 and ZK 98299. Both Org compounds are strong antiprogestagens with little antiglucocortocoid activity and are devoid of other hormonal activities except for some weak androgenic and anti-androgenic activity. The two compounds are more potent than RU38486 and ZK 98299 with respect to their anti-progestational activity and are more selective. The Org compounds are effective in inhibiting the development of tumours in the 7,12-dimethylbenz(a)anthracene (DMBA) rat model. Org 31710 and Org 31806 may be applied for both the treatment of breast tumours and the improvement of fertility control.