Fulvestrant - A Novel Endocrine Therapy for Breast Cancer

Fulvestrant is a novel endocrine therapy for breast cancer, with a unique structure and mode of action. It binds competitively to the oestrogen receptor (ER), with high affinity, and downregulates ER by functional blockade and increased turnover. Fulvestrant has reached the clinic via extensive pre-clinical and clinical trials, which demonstrated fulvestrant's unique characteristics and showed that they translate to equivalent or improved clinical efficacy compared to established endocrine agents. Fulvestrant is currently licensed for use in postmenopausal women with hormone receptor positive advanced breast cancer which has progressed on prior endocrine therapy. As a pure oestrogen antagonist, fulvestrant avoids the risk of detrimental side effects of selective ER modulators such as tamoxifen, which has partial agonist activity. Fulvestrant, the only parenteral agent in this setting, has a good side effect profile and is well tolerated. Due to its unique mode of action, fulvestrant lacks cross-resistance with existing agents. Fulvestrant is the subject of much ongoing research, which utilises knowledge of its novel mechanism and pharmacokinetic profile in order to optimise clinical efficacy and explore new roles, including first-line use in advanced breast cancer, use in combination with existing agents, in males, and in premenopausal women, and use as an adjuvant therapy.