(Z)-Endoxifen for the Treatment of Premenopausal Women With ER+/HER2- Breast Cancer (NCT05607004)
A Phase 2 Trial of (Z)-Endoxifen + Goserelin as Neoadjuvant Treatment for Premenopausal Women With ER+, HER2-, Breast Cancer
🩺 Plain-English Summary (8th-Grade Level)
This open-label research study is studying (Z)-endoxifen as a possible treatment for pre-menopausal women with ER+/HER2- breast cancer. (Z)-endoxifen belongs to a group of drugs called selective estrogen receptor modulators or "SERM", which help block estrogen from attaching to cancer cells. This study has two parts: a pharmacokinetic part and a treatment part. The PK part (how the body processes the drug) will enroll about 18 participants. All participants will take (Z)-endoxifen capsules daily. Twelve participants will be randomly assigned (50/50 chance) to take (Z)-endoxifen alone or (Z)-endoxifen with a monthly injection of goserelin a drug that temporarily stops the ovaries from making estrogen. This part will help determine the best dose of (Z)-endoxifen by measuring the drug levels in the blood and how long the body takes to remove it. The Treatment Cohort has been simplified to a single study arm (Z)-endoxifen + goserelin. Up to 20 participants will be enrolled that have a baseline Ki-67 ≤ 10% and 45 participants will be enrolled that have a baseline Ki-67\>10%. A key goal of the study is to see if (Z)-endoxifen can slow down or stop tumor growth as measured by a reduction in Ki-67 levels. Tumor tissue samples will be taken by breast biopsy after about 4 weeks of treatment to check levels of this biomarker. If the tumor shows signs of response, participants can continue treatment for up to 24 weeks or until they have surgery. Study participation is up to 6 months (24 weeks of treatment) followed by surgery and a one-month follow up visit.
Who can join: Review the eligibility criteria below.
Location: Mayo Clinic Arizona — Phoenix, Arizona
Age range: 18 Years
🧪 Interventions in This Study
📋 "Do I Qualify?" — 1-Minute Self Screener
Instant ChecklistFull eligibility criteria are available on the official NIH protocol. View the criteria ↗
📍 All Participating Trial Locations (14 Sites)
- Mayo Clinic Arizona — Phoenix, Arizona
- University of Arizona — Tucson, Arizona
- California Research Institute — Los Angeles, California
- Mayo Clinic Florida — Jacksonville, Florida
- Northwestern University — Chicago, Illinois
- St. Elizabeth Healthcare — Edgewood, Kentucky
- Henry Ford Cancer Institute — Detroit, Michigan
- Mayo Clinic Rochester — Rochester, Minnesota
- Washington University School of Medicine — St Louis, Missouri
- Avera Cancer Institute — Sioux Falls, South Dakota
- Vanderbilt Ingram Cancer Center — Nashville, Tennessee
- Baylor University — Houston, Texas
- Bon Secours Cancer Institute — Midlothian, Virginia
- Fred Hutchinson Cancer Center — Seattle, Washington
📞 Contact the Study Coordinator
Phone: (800) 664-4580
Coordinator details come directly from the registered NIH protocol. Confirm the study is still recruiting before traveling.
💰 Cost, Insurance & Patient Rights
- 100% Free Items: The investigational treatment and protocol-required procedures are supplied at zero cost by the sponsor.
- Routine Patient Care: Under federal law (ACA § 2709) and many state statutes, routine care costs are covered during participation.
- Voluntary Participation: You may withdraw at any time without affecting your standard medical care.
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💡 How to Participate
- Check the checklist above to see if you may qualify.
- Contact the study coordinator using the phone/email above.
- Ask about the visit schedule, what is covered at no cost, and any travel support.
- Confirm with your own doctor before making a decision.