1.Selective oestrogen receptor modulators (SERMs)

The "selective" in the acronym SERMs alludes to the unique regulation of the oestrogen receptor and the downstream effect on ER signalling that happens inside various organs. Tamoxifen, for example, is known to have anti-proliferative (or antagonistic) effects in breast tissue while having agonistic or partial agonistic effects on the uterus, bone, and heart. In both the usage of SERMs and the creation of new medicines, the ratio of therapeutic benefit to negative tissue-specific effects has been an essential factor to address [46].

## a.Tamoxifen

Tamoxifen has been effectively used to treat breast cancer in both premenopausal and postmenopausal women at all stages. It's utilised as a palliative treatment for those who have advanced cancer, as well as an adjuvant treatment after surgery for node-negative or positive cancer. Tamoxifen has consistently prolonged diseasefree intervals as a postsurgical adjuvant therapy for early breast cancer with a low frequency of side effects. It is possible to achieve a 20% decrease in 5-year mortality, with the reduction being most noticeable in women over 50. Tamoxifen is used to reduce the risk of breast cancer and invasive breast cancer in women who are at high risk for the disease, as well as those who have ductal carcinoma in situ. Negative oestrogen receptor tumours do not respond to treatment [47].
