Clinical studies with the specific ‘pure’ antioestrogen ICI 182780

We have shown that ICI 182780 inhibits the growth of metastatic tumour cells derived from patients failing treatment with tamoxifen when grown in vitro. In this system tamoxifen stimulates growth of tumour cells which can be reversed by addition of ICI 182780 to tamoxifen in culture. In a phase I study we have demonstrated that treatment of patients for 7 days before surgical excision of the tumour resulted in marked down regulation of ER, inhibition of growth and oestrogen-induced gene expression. More recently we demonstrated that treatment of advanced breast cancer patients with ICI 182780, after tamoxifen failure, resulted in a high remission rate and prolonged periods of remission with very few side-effects. These data indicate that further clinical trials of ICI 182780 are warranted. We expect that it will show superiority over conventional endocrine therapy.