OncoMatch/Clinical Trials/NCT05607004
(Z)-Endoxifen for the Treatment of Premenopausal Women With ER+/HER2- Breast Cancer
Is NCT05607004 recruiting? Yes, currently enrolling (May 2026). This Phase 2 trial studies multiple treatments including (Z)-endoxifen and goserelin for breast neoplasms.
Treatment: (Z)-endoxifen · goserelin — 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.
Check if I qualifyExtracted eligibility criteria
Cancer type
Breast Carcinoma
Biomarker criteria
Required: ESR1 strongly positive (≥ 67% or Allred Score 6-8) (≥ 67% or Allred Score 6-8)
strongly estrogen receptor positive (ER+) (defined as estrogen receptor [ER] ≥ 67% or Allred Score 6-8)
Required: HER2 (ERBB2) negative
HER2- breast cancer (histologically confirmed) using ASCO/CAP guidelines
Disease stage
Required: Stage CLINICAL T2, CLINICAL T3, CLINICAL N0, CLINICAL N1 (AJCC 8th edition)
Grade: Nottingham (Elston-Ellis) Grade 1Nottingham (Elston-Ellis) Grade 2 (Nottingham (Elston-Ellis))
Clinical T2 or T3 invasive breast cancer (per American Joint Committee on Cancer [AJCC] 8th edition clinical staging); Clinical N0 or N1 invasive breast cancer (per AJCC 8th edition); Nottingham (Elston-Ellis) Grade 1 or 2
Performance status
ECOG 0–2(Ambulatory, capable of self-care)
Prior therapy
Cannot have received: hormonal therapy (birth control, hormone replacement therapy, androgen-based therapy)
Exception: Depo-Provera®: last dose of 3-month contraceptive agents > 2.5 months from registration
Hormonal therapies including birth control and hormone replacement therapy, or prior use of androgen-based therapy during the study or within 1 week of registration. If subject has a prior medical history of Depo-Provera®, it is recommended that the last dose of 3-month contraceptive agents are > 2.5 months from registration.
Cannot have received: any prior breast cancer therapy
Prior diagnosis or treatment for breast cancer, including carcinoma in situ
Lab requirements
Blood counts
Platelet count > 75,000/mm3; Hemoglobin > 10 g/dL
Liver function
Total bilirubin < 1.5 x ULN; AST/ALT < 2.5 x ULN
Evidence of the following laboratory abnormalities ≤ 28 days prior to registration: Total bilirubin ≥ 1.5 x ULN; AST or ALT ≥ 2.5 x ULN; Platelet count ≤ 75,000/mm3; Hemoglobin ≤ 10 g/dL
Structured fields extracted by AI. May contain errors — verify against the official protocol.
US trial 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
Showing up to 5 US sites. See all sites on ClinicalTrials.gov →
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