Endoxifen HCl is primarily used in the treatment of breast cancer, particularly for hormone receptor-positive types. It functions as a selective estrogen receptor modulator (SERM), effectively blocking estrogen's effects on breast tissue, which can help inhibit the growth of cancer cells. This compound is often considered in cases where other treatments, such as tamoxifen, are less effective due to metabolic variations in patients. Additionally, Endoxifen HCl is being researched for its potential in preventing breast cancer recurrence and its use in premenopausal women with early-stage breast cancer. Its targeted action makes it a valuable option in personalized cancer therapy, especially for individuals with specific genetic profiles that affect drug metabolism.