Afimoxifene
Afimoxifene is a selective estrogen receptor modulator of the triphenylethylene group and the major active metabolite of tamoxifen. The drug is under development under the tentative brand name TamoGel as a topical gel for the treatment of hyperplasia of the breast. It has completed a phase II clinical trial for cyclical mastalgia, but further studies are required before afimoxifene can be approved for this indication and marketed.
Afimoxifene is a SERM and hence acts as a tissue-selective agonist–antagonist of the estrogen receptors ERα and ERβ with mixed estrogenic and antiestrogenic activity depending on the tissue. It is also an agonist of the G protein-coupled estrogen receptor with relatively low affinity. In addition to its estrogenic and antiestrogenic activity, afimoxifene has been found to act as an antagonist of the estrogen-related receptors ERRβ and ERRγ.
