PHARMACOLOGY OF 2 NEW VERY SELECTIVE ANTIPROGESTAGENS - ORG-31710 ANDORG-31806

Org 31710 and Org 31806 are new antiprogestagens. These compounds were tested for their binding affinity to various steroid receptors and fo r their bio-activity in various animal models and the results were com pared with those of RU38486 and ZK 98299. Both Org compounds are stron g antiprogestagens with little antiglucocortocoid activity and are dev oid of other hormonal activities except for some weak androgenic and a nti-androgenic activity. The two compounds are more potent than RU3848 6 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) ra t model. Org 31710 and Org 31806 may be applied for both the treatment of breast tumours and the improvement of fertility control.