Brilanestrant is primarily used in the treatment of hormone receptor-positive (HR+) breast cancer. It functions as a selective estrogen receptor degrader (SERD), effectively targeting and degrading estrogen receptors in cancer cells. This action helps to inhibit the growth of cancer cells that rely on estrogen for proliferation. It is particularly beneficial for postmenopausal women with advanced or metastatic breast cancer, offering a therapeutic option for those who may have developed resistance to other hormonal therapies. Additionally, brilanestrant is being explored in combination with other treatments, such as CDK4/6 inhibitors, to enhance its efficacy and improve patient outcomes. Its oral administration provides a convenient alternative to injectable SERDs, improving patient compliance and quality of life.