New Tamoxifen-Like drug tested for stubborn hormone cancers
NCT ID NCT01273168
First seen Jun 25, 2026 · Last updated Jun 27, 2026 · Updated 1 time
Summary
This early-stage trial tested an experimental drug called Z-Endoxifen in 40 adults with hormone receptor-positive cancers (like breast, ovarian, or desmoid tumors) that had stopped responding to standard treatments. Z-Endoxifen is a direct form of tamoxifen's active ingredient, bypassing the need for liver conversion. The main goal was to check safety and find the right dose, while also seeing if it could slow tumor growth.
What this could mean
Our plain-language read of the trial. This is informational only, not medical advice or a prediction.
- Active substance
- Z-Endoxifen (an active form of tamoxifen)
- What this could lead to
- If it works, this could provide a treatment option for people with hormone-positive cancers that no longer respond to standard therapies.
- What could go wrong
- This is an early Phase 1 trial with only 40 participants, so safety and dosing are the main focus—not yet proof of effectiveness. The drug may cause side effects or fail to shrink tumors.
This is an AI summary of the original study and may miss details. Read our disclaimer.
Study facts
What this study's own registry entry says, in plain language.
- Phase
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Phase 1
The first testing in people. Mainly checks safety and dose, usually in a small group.
- Participants
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40 people
The number who actually took part.
- Started
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Mar 2011
- Finished
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Dec 2025
- Lead sponsor
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A government research agency
The lead sponsor is the US National Institutes of Health.
Who can take part
This study's own entry requirements. Only the study team can say for certain whether you qualify.
- Ages
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18 to 120 years
- Sex
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Anyone
- Healthy volunteers
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Not accepted
This study is not open to healthy volunteers. The entry requirements below say who it is open to.
Show the full entry requirements Hide the full entry requirements
Copied word for word from the study's registry entry, so the wording is the study team's rather than ours.
* INCLUSION CRITERIA: Patients with the following types of histologically documented solid tumors: * ER +/PR+, ER+/PR-, or ER-/PR+ breast cancer * Gynecologic tumors (endometrial, ovarian, uterine, fallopian tube, peritoneal, etc.) * Desmoid tumors * Tumors that are ER+ or PR+ by immunohistochemistry (including low-level expression) such as non-small cell lung, colorectal, and prostate Patients with breast cancer must have had at least one prior chemotherapy regimen for metastatic disease. Additionally, patients with breast cancer must have received prior tamoxifen and/or aromatase inhibitor therapy (if postmenopausal) with at least one hormonal regimen in the metastatic setting. Patients with HER2+ breast cancer must have progressed after at least one prior HER2-directed regimen (trastuzumab, lapatinib) for metastatic disease. All other patients must have disease that has progressed following at least one line of standard therapy. Prior therapy with tamoxifen is allowed. Patients enrolled based on tumor ER/PR status must have ER/PR status confirmed by the Laboratory of Pathology, NIH. ER/PR status will be determined on a metastatic site, if possible; otherwise, the original site or available tissue will be acceptable. Patients must have recovered to at least eligibility levels following any display of adverse events and/or toxicity due to prior chemotherapy or biologic therapy. They must not have had hormonal therapy, chemotherapy or biologic therapy within 4 weeks prior to entering the study (6 weeks for nitrosoureas or mitomycin C, or UCN-01). Patients must be greater than or equal 2 weeks since any prior administration of study drug in a Phase 0 study (also referred to as an "early Phase I study" or "pre-Phase I study" where a sub-therapeutic dose of drug is administered) at the PI's discretion. Patients must be greater than or equal to 4 weeks since any prior radiation or major surgery. However, patients receiving bisphosphonates or therapeutic anticoagulation are eligible for this trial. Age greater than or equal 18 years The Eastern Cooperative Oncology Group (ECOG) performance status less than or equal to 2 Life expectancy \> 3 months Patients must have normal or adequate organ and marrow function as defined below: Absolute neutrophil count greater than or equal to 1,500/microL Platelets greater than or equal to 100,000/microL Total bilirubin within less than or equal to 1.5 times institutional upper limit of normal AST (SGOT)/ALT (SGPT) less than or equal to 2.5 times institutional upper limit of normal Creatinine \< 1.5 times upper limit of normal OR Creatinine clearance greater than or equal to 60 mL/min/1.73 m(2) for patients with creatinine levels greater than or equal to 1.5 times upper limit of normal. The effects of Z-endoxifen on the developing human fetus are unknown. For this reason, women of childbearing potential and men must agree to use adequate nonhormonal contraception (barrier method of birth control or abstinence) prior to study entry, for the duration of study participation, and for 2 months after discontinuation from the study. Women of childbearing potential must have a negative pregnancy test in order to be eligible. Should a woman become pregnant or suspect she is pregnant while participating in this study, she should inform her treating physician immediately. Because there is an unknown but potential risk for adverse events in nursing infants secondary to treatment of the mother with Z-endoxifen, breastfeeding should be discontinued if the mother is treated with Z-endoxifen. Ability to understand and the willingness to sign a written informed consent document. EXCLUSION CRITERIA: Patients receiving any other investigational agents. Patients with known brain metastases are excluded from this clinical trial, with the exception of patients whose brain metastatic disease status has remained stable for greater than or equal to 3 months after treatment of the brain metastases, without steroids or anti-seizure medications. These patients may be enrolled at the discretion of the principal investigator. Patients with clinically significant illnesses which could compromise participation in the study, including, but not limited to, uncontrolled infection, uncontrolled diabetes, uncontrolled hypertension, symptomatic congestive heart failure, unstable angina pectoris, myocardial infarction within the past 6 months, uncontrolled cardiac arrhythmia, stroke/cerebrovascular accident within the past 6 months, or psychiatric illness/social situations that in the investigator s opinion would make it undesirable for the patient to participate in the trial, or which would jeopardize compliance with the protocol. Patients with untreated spinal cord metastases or metastases close to vital organs (as determined by the principal investigator) are excluded because of the risk of hormonal flare. Patients with a history of deep vein thrombosis must be on anti-coagulation therapy prior to enrollment. Patients requiring prophylactic anti-coagulation are eligible.
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Conditions
The condition(s) this trial relates to.
As listed by the trial registrant
The condition terms exactly as the trial's registrant entered them.
Contacts and locations
Locations
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National Institutes of Health Clinical Center
Bethesda, Maryland, 20892, United States
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