Published online by Cambridge University Press: 18 June 2020
SERMs (selective estrogen receptor modulators) are unique synthetic compounds that bind to the estrogen receptor and, depending on their unique conformational change, will either initiate estrogen agonistic activity or antagonistic activity. There are many that have come to market and others that have not. The first, for all practical purposes, was tamoxifen (although, clomiphene citrate is often considered a SERM). Approved in the US for treatment of breast cancer in 1978, tamoxifen became the most widely prescribed anti-cancer drug worldwide. When news of its ability to cause a small number of endometrial carcinomas surfaced, there was renewed interest in the SERM raloxifene, whose preclinical work suggested that, in experimental animals, it behaved differently in the uterus. In the US, Raloxifene was approved for prevention of osteoporosis in 1997, treatment of osteoporosis in 1999, and breast cancer risk reduction in 2009. Tamoxifen is also currently approved for breast cancer risk reduction.