Pure anti-oestrogens

Pure anti-oestrogens are a group of at least five new compounds which are able to antagonize the effects of oestrogen in all tissues and species studied. The mechanism by which the pure anti-oestrogens produce their effects remains in question, but all of them are competitive antagonists of the oestrogen receptors and, moreover, have been proposed to block the shuttling of oestrogen receptors into the cell nucleus. When studied in vitro, these compounds are able to block the oestrogen-stimulated growth of breast cancer cells. In animals, their ability to block the effects of oestrogen on breast, uterus, bone, cardiovascular system and other reproductive-associated tissues has been demonstrated. ICI 182780 has been used in preliminary clinical trials in women with advanced, tamoxifen-resistant breast cancer with promising results. Clinical trials with EM-800 are under way to assess the safety and tolerance and to obtain information on its efficacy in patients who have already been treated with tamoxifen. It seems reasonable to assume that pure anti-oestrogens will be a good alternative to tamoxifen in the treatment of breast cancer and also in some non-malignant gynaecological diseases.