Toremifene

Hormonal / PCT

Also known as: Fareston, Toremifene Citrate

Selective Estrogen Receptor ModulatorsResearch phase: FDA-approvedRegulatory: FDA-approved for metastatic breast cancer in postmenopausal women (1997). Available by prescription as Fareston.

Mechanism

Toremifene is a chlorinated derivative of tamoxifen FDA-approved for metastatic breast cancer. It has a similar mechanism to tamoxifen but with a potentially improved safety profile — it shows less DNA adduct formation (a marker of genotoxicity) and reduced endometrial cancer risk. It is sometimes used as a tamoxifen alternative for PCT.

Technical detail

Toremifene is a first-generation triphenylethylene SERM structurally identical to tamoxifen except for a chlorine substitution at position 4. This modification reduces the formation of reactive metabolite intermediates and DNA adducts associated with tamoxifen's genotoxic potential. It demonstrates equivalent ER antagonism in breast tissue, similar bone-protective partial agonism, but reduced uterotrophic activity and endometrial carcinoma risk compared to tamoxifen. It blocks hypothalamic-pituitary ER negative feedback similar to tamoxifen, supporting its off-label use in PCT protocols.

Build a personalized protocol with Toremifene →