Endoxifen hydrochloride is primarily used in the treatment and prevention of breast cancer, particularly in estrogen receptor-positive (ER+) cases. It acts as a selective estrogen receptor modulator (SERM), effectively blocking estrogen's effects on breast tissue, which helps inhibit the growth of cancer cells. This compound is often considered a more potent alternative to tamoxifen due to its higher affinity for estrogen receptors. It is also being studied for its potential in reducing the risk of cancer recurrence and as a therapeutic option for patients who may not respond well to other treatments. Additionally, research is exploring its role in managing other hormone-dependent conditions.