IDOXIFENE - REPORT OF A PHASE-I STUDY IN PATIENTS WITH METASTATIC BREAST-CANCER

Idoxifene, a novel antiestrogen with reduced estrogenic activity when compared to tamoxifen, has been given to 20 women with metastatic brea st cancer, 19 of whom had received tamoxifen previously, in doses betw een 10-60 mg. Idoxifene had an initial half-life of 15 h and a termina l half-life of 23.3 days, At a maintenance dose of 20 mg, a mean stead y-state level of 173.5 ng/ml was achieved. Significant falls in lutein izing hormone and follicle-stimulating hormone were seen, but the fall s were not dose related. Idoxifene was well tolerated, with 11 patient s complaining of mild symptoms similar to those seen with tamoxifen, F ourteen patients continued idoxifene therapy for 1-56 weeks; 4 patient s showed stabilization of disease for 6-56 weeks and 2 patients showed a partial response.