Endoxifen in Adults With Hormone Receptor Positive Solid Tumors

Genetic polymorphisms in CYP2D6 and concomitant medications alter tamoxifen metabolism, limiting exposure to the active metabolite endoxifen. These factors are associated with a higher rate of recurrence and shorter disease-free survival in breast cancer patients receiving tamoxifen. Administration of endoxifen directly to patients is anticipated to bypass the effects of CYP2D6 polymorphisms and concomitant medications and provide adequate active drug levels in all treated patients, resulting in clinical benefit.