Norendoxifen
Norendoxifen, also known as 4-hydroxy-N,''N''-didesmethyltamoxifen, is a nonsteroidal aromatase inhibitor of the triphenylethylene group that was never marketed.
It is an active metabolite of the selective estrogen receptor modulator tamoxifen. Unlike tamoxifen, norendoxifen is not a SERM, and instead has been found to act as a potent and selective competitive inhibitor of aromatase. Drugs with dual SERM and AI activity, such as 4'-hydroxynorendoxifen, have been developed from norendoxifen, and may have therapeutic potential as antiestrogens in the treatment of estrogen receptor-positive breast cancer.