Effect of toremifene on estrogen primed vaginal mucosa in postmenopausal women

Toremifene. A review of its pharmacological properties and clinical efficacy in the management of advanced breast cancer

The triphenylethylene antiestrogen toremifene is a chlorinated derivative of the antiestrogen tamoxifen, an agent which has been widely and successfully used in the treatment of breast cancer. Clinical trials investigating the efficacy of toremifene as first-line endocrine therapy in postmenopausal women with advanced breast cancer (estrogen receptor status positive or unknown) have shown this drug to have similar antitumour activity to that of tamoxifen. In multicentre comparative trials, objective responses (complete and partial) occurred in 20 to 29% of patients treated with toremifene (60 to 240 mg/day) and in 19 to 37.5% of tamoxifen (20 or 40 mg/day) recipients. The duration of response, time to disease progression and median overall survival time were generally similar in both treatment groups. Toremifene is well tolerated. Most drug-related adverse effects are mild or moderate in severity and rarely necessitate discontinuation of therapy. The tolerability profile of toremifene is similar to that reported for tamoxifen, the most common adverse effects being hot flushes, sweating, nausea and/or vomiting, dizziness, oedema, and vaginal discharge and/or bleeding. Thus, toremifene provides an equally effective and well tolerated alternative to tamoxifen for the first-line endocrine therapy of postmenopausal advanced breast cancer. Preclinical studies showing toremifene to have a lower carcinogenic potential than tamoxifen indicate that toremifene may be a preferable agent for long term treatment regimens; however, these findings require confirmation in the clinical setting.

Agonistic and antagonistic effects of antiestrogens in different target organs

Antiestrogens block by definition specifically the actions of estrogens. In the classical uterotropic assay in immature rodents, where estrogens cause fluid retention and cell proliferation, triphenylethylenes have also species-specific estrogen-like (agonistic) effects. 4-hydroxylated triphenylethylenes have in general less estrogenic properties than unhydroxylated ones, and ICI 164,384 has no estrogenic activity in this model. Uterus responds to estrogens by stimulation of cell proliferation. Some other tissues, like breast, liver, and bone respond by regulation of specific protein synthesis. Some of the proteins act as growth factors, and some have unknown functions. The regulation of gene expression is a complex phenomenon: estrogens may turn the responsive gene on or off. Similarly antiestrogens may participate in the gene regulation by mimicking or antagonising estrogen-like actions. This paper summarizes the estrogenic and antiestrogenic effects of classical and new antiestrogens in different tissues.