A Phase I Study to See if Endoxifen Gel, a Form of Tamoxifen, Can Be Delivered to the Breast through the Skin


Full Title

NWU2017-09-01: Phase I Trial of Endoxifen Gel Versus Placebo Gel in Women Undergoing Breast Surgery (CIRB)


Tamoxifen is an anti-estrogen hormonal therapy used to both treat and prevent breast cancers that are positive for estrogen receptors. Many women who could benefit from tamoxifen to reduce their breast cancer risk do not take this medication because when taken by mouth, it can cause uncomfortable side effects because it travels throughout the bloodstream to all parts of the body.

In this study, researchers are determining if endoxifen (a metabolite of tamoxifen) in gel form can be delivered to breast tissue through the skin. Women who will be having a single or double mastectomy will apply one of two doses of endoxifen gel or a placebo (inactive) gel to both breasts for about four weeks before surgery. Researchers will see if endoxifen gel can be applied to the breast without causing skin irritation and also determine how much of the medication at each dose gets into breast tissue and into the blood.

In this study, endoxifen is not meant to treat a participant’s breast cancer and will not interfere with her usual treatment, but rather will aid in determining in endoxifen gel could be an alternative option for breast cancer prevention in the future.

Women in this study will be randomly assigned to one of three groups:

  • One of two doses of endoxifen gel up until the day before surgery.
  • Placebo gel until the day before surgery.
  • The best dose of endoxifen identified earlier in the study but stopped three days before surgery. This will allow the researchers to learn how long endoxifen stays in the breast after a woman stops applying it.


To be eligible for this study, patients must meet several criteria, including but not limited to the following:

  • Patients must be planning to have a single or double mastectomy at Memorial Sloan Kettering for stage 0-III breast cancer or for prophylactic reasons (such as carrying a BRCA mutation).
  • Patients may not have taken tamoxifen or other estrogen/progesterone modulating drugs within two years of entering the study.
  • Patients must be physically well enough that they are fully ambulatory, capable of all self care, and are capable of all but physically strenuous activities. As an example, patients must be well enough that they would be able to carry out office work or light housework.
  • This study is for women age 18 and older.

For more information about this study and to inquire about eligibility, please contact Dr. Melissa Pilewskie at 646-888-4675.





Disease Status

Newly Diagnosed