New anticancer drugs are usually developed specially for the
job, but occasionally they are borrowed from another field of
medicine, and applied speculatively in cancer. Tamoxifen was
designed as an anti-oestrogen, based on the observation that at
least a third of breast cancers depend on female sex hormones
such as oestrogen for survival. Tamoxifen has shown to be an
exceptionally effective molecule in cancer treatment; It was
never planned to be a preventive agent, but so it has proved to
be! It is now licensed to be used to prevent breast cancer in
certain women at high risk of the disease. Contrast this with
raloxifene, a drug first developed to treat osteoporosis in
women. A selective benzothiophene oestrogen receptor modulator
(SERM), raloxifene binds to oestrogen receptors as a mixed
oestrogen and anti-oestrogen effect. It functions as an
oestrogen sometimes (in bones and on lipid metabolism) and as an
anti-oestrogen in other target tissues (endometrium and breast).
So, it has the potential for produci