A Study of Imlunestrant (LY3484356) in Premenopausal Women With Estrogen Receptor-Positive (ER+) Human Epidermal Growth Factor Receptor 2 Negative (HER2-) Early Breast Cancer
preEMBER
preEMBER: A Phase 2, Open-label Study Evaluating Imlunestrant in Premenopausal Women With Estrogen Receptor-Positive, HER2-Negative Breast Cancer
3 other identifiers
interventional
600
6 countries
42
Brief Summary
This study will include two groups of patients: Cohort 1 and Cohort 2. Cohort 1: will help researchers learn how a medicine called imlunestrant (LY3484356) affects a specific type of breast cancer. Some patients will take both imlunestrant and another treatment to suppress their ovarian function. Some will take it without ovarian suppression. Researchers will compare the effects in breast cancer cells to those of another medicine called tamoxifen. All patients in this group will be premenopausal women who have a type of early breast cancer called estrogen receptor-positive, HER2-negative. The treatment in this group will last for up to 29 days. Cohort 2: will help researchers understand how imlunestrant affects the ovaries when it is taken without ovarian suppression. Researchers will compare the effects to those of another medicine called tamoxifen. This group will also include premenopausal women with the same type of breast cancer. The treatment in this group will last for up to 6 months.
Trial Health
Trial Health Score
Automated assessment based on enrollment pace, timeline, and geographic reach
participants targeted
Target at P75+ for phase_2
Started May 2026
Typical duration for phase_2
42 active sites
Health score is calculated from publicly available data and should be used for screening purposes only.
Trial Relationships
Click on a node to explore related trials.
Study Timeline
Key milestones and dates
First Submitted
Initial submission to the registry
December 11, 2025
CompletedFirst Posted
Study publicly available on registry
December 17, 2025
CompletedStudy Start
First participant enrolled
May 1, 2026
CompletedPrimary Completion
Last participant's last visit for primary outcome
January 1, 2029
ExpectedStudy Completion
Last participant's last visit for all outcomes
December 1, 2029
April 17, 2026
April 1, 2026
2.7 years
December 11, 2025
April 16, 2026
Conditions
Outcome Measures
Primary Outcomes (2)
Change from Baseline in Antigen Kiel (Ki-67) Expression
Baseline, Day 29
Rate of Symptomatic Ovarian Cysts
Up to Day 180
Secondary Outcomes (3)
Change from Baseline in Estrogen Receptor (ER) Expression
Baseline, Day 29
Change from Baseline in Progesterone Receptor (PR) Expression
Baseline, Day 29
Rate of Complex Ovarian Cysts
Up to Day 180
Study Arms (5)
Cohort 1 Arm A
EXPERIMENTALImlunestrant will be given orally
Cohort 1 Arm B - Imlunestrant + Goserelin
EXPERIMENTALImlunestrant will be given orally and goserelin will be given subcutaneously (SC)
Cohort 1 Arm C - Tamoxifen
ACTIVE COMPARATORTamoxifen will be given orally
Cohort 2 Arm A - Imlunestrant
EXPERIMENTALImlunestrant will be given orally
Cohort 2 Arm B - Tamoxifen
ACTIVE COMPARATORTamoxifen will be given orally
Interventions
Given orally
Eligibility Criteria
You may qualify if:
- Cohort 1:
- Have histologically confirmed Stage I to III Estrogen Receptor positive (ER+), human epidermal growth factor receptor 2 negative (HER2-) invasive breast carcinoma with Ki-67 at least 10%
- Be willing and able to provide pre- and on-treatment tumor samples.
- Have an Eastern Cooperative Oncology Group (ECOG) performance status of 0 or 1.
- Be able to swallow capsules or tablets.
- Be premenopausal women.
- If of childbearing potential must use 1 highly effective method of non-hormonal contraception while receiving study treatment and for the duration specified in protocol.
- Have adequate organ function.
- Cohort 2:
- Have a diagnosis of ER+, HER2- early-stage, resected, invasive breast cancer without evidence of distant metastasis
- Have undergone definitive loco-regional therapy.
- Have received at least 4.5 years of any adjuvant endocrine therapy (ET), or at least 2 years of adjuvant ET with no additional ovarian suppression planned.
- Have an Eastern Cooperative Oncology Group (ECOG) performance status of 0 or 1.
- Be able to swallow capsules or tablets.
- Be premenopausal women
- +2 more criteria
You may not qualify if:
- Cohort 1:
- Have bilateral invasive metastatic, occult primary, or inflammatory breast cancer.
- Have had prior bilateral oophorectomy or ovarian ablation.
- Have a serious medical condition
- Had major surgery within 28 days prior to randomization.
- Have a history of other cancer (except non melanoma skin cancer, Stage I uterine cancer, or carcinoma in situ of the cervix or other in situ cancer), unless in complete remission with no therapy for a minimum of 1 year.
- Plan to receive concurrent neoadjuvant therapy with any other non-protocol anticancer therapy.
- Have had any prior therapy for an invasive or non-invasive breast cancer.
- Have had prior radiotherapy to the ipsilateral chest wall for any malignancy.
- Have received prior anti-estrogen therapy, including for osteoporosis or prevention of breast cancer.
- Have had prior treatment with any Gonadotropin-releasing hormone (GnRH) agonist within 12 months prior to randomization.
- Receiving current exogenous reproductive hormone therapy
- Cohort 2:
- Have ovarian cyst(s) greater than (\>) 1 centimeter (cm) at screening.
- Have metastatic occult primary, or inflammatory breast cancer.
- +7 more criteria
Contact the study team to confirm eligibility.
Sponsors & Collaborators
Study Sites (42)
Banner MD Anderson Cancer Center at North Colorado Medical Center
Greeley, Colorado, 80631, United States
Banner MD Anderson Cancer Center at McKee Medical Center
Loveland, Colorado, 80538, United States
Indiana University Melvin and Bren Simon Cancer Center
Indianapolis, Indiana, 46202, United States
Dana-Farber Cancer Institute
Boston, Massachusetts, 02215, United States
Washington University School of Medicine
St Louis, Missouri, 63110, United States
Tennessee Oncology
Nashville, Tennessee, 37203, United States
University of Texas MD Anderson Cancer Center
Houston, Texas, 77030-4009, United States
Houston Methodist Hospital
Houston, Texas, 77030, United States
Oncology Consultants P.A.
Houston, Texas, 77030, United States
Inova Schar Cancer Institute
Fairfax, Virginia, 22031, United States
Cliniques universitaires Saint-Luc
Brussels, 1200, Belgium
Antwerp University Hospital
Edegem, 2650, Belgium
UZ Leuven
Leuven, 3000, Belgium
CHRU de Brest
Brest, 29609, France
Centre de Cancérologie du Grand Montpellier
Montpellier, 34070, France
Hôpital Privé Des Côtes d'Armor
Plérin, 22190, France
Institut Curie - site Saint-Cloud
Saint-Cloud, 92210, France
Onkologische Schwerpunktpraxis Bielefeld
Bielefeld, 33604, Germany
Medizinische Universität Lausitz- Carl Thiem
Cottbus, 03048, Germany
Universitaetsklinikum Erlangen
Erlangen, 91054, Germany
Kliniken Essen-Mitte, Evangelische Huyssens-Stiftung
Essen, 45136, Germany
Agaplesion Markus Krankenhaus
Frankfurt, 60431, Germany
Frauenärzte am Bahnhofsplatz
Hildesheim, 31134, Germany
Evangelisches Krankenhaus Bethesda Mönchengladbach
Mönchengladbach, 41061, Germany
Klinikum der Ludwig-Maximilians-Universitaet Muenchen
München, 80336, Germany
Rotkreuzklinikum München gemeinnützige GmbH
München, 80637, Germany
Klinikum Mutterhaus der Borromäerinnen
Trier, 54290, Germany
Hämatologisch-Onkologische Schwerpunktpraxis
Troisdorf, 53840, Germany
Universitaetsklinikum Tuebingen
Tübingen, 72076, Germany
Marien Hospital Witten
Witten, 58452, Germany
HELIOS Klinikum Wuppertal
Wuppertal, 42283, Germany
Ente Ospedaliero Ospedali Galliera
Genova, 16128, Italy
Humanitas
Milan, 20089, Italy
Humanitas Istituto Clinico Catanese
Misterbianco, 95045, Italy
Nuovo Ospedale di Prato-S.Stefano
Prato, 59100, Italy
Fondazione Policlinico Universitario Agostino Gemelli
Roma, 00168, Italy
Kaohsiung Medical University Chung-Ho Memorial Hospital
Kaohsiung City, 807, Taiwan
China Medical University Hospital
Taichung, 404332, Taiwan
Taichung Veterans General Hospital
Taichung, 407, Taiwan
National Cheng Kung University Hospital
Tainan, 704, Taiwan
Mackay Memorial Hospital
Taipei, 10449, Taiwan
Chang Gung Medical Foundation-Linkou Branch
Taoyuan District, 333, Taiwan
Related Links
MeSH Terms
Conditions
Interventions
Condition Hierarchy (Ancestors)
Intervention Hierarchy (Ancestors)
Study Officials
- STUDY DIRECTOR
Call 1-877-CTLILLY (1-877-285-4559) or 1-317-615-4559 Mon - Fri 8 AM - 8 PM Eastern time (UTC/GMT - 5 hours, EST)
Eli Lilly and Company
Central Study Contacts
Trial questions or participation questions: 1-877-CTLILLY (1-877-285-4559) or
CONTACT
Physicians interested in becoming principal investigators please contact
CONTACT
Study Design
- Study Type
- interventional
- Phase
- phase 2
- Allocation
- RANDOMIZED
- Masking
- NONE
- Purpose
- TREATMENT
- Intervention Model
- PARALLEL
- Sponsor Type
- INDUSTRY
- Responsible Party
- SPONSOR
Study Record Dates
First Submitted
December 11, 2025
First Posted
December 17, 2025
Study Start
May 1, 2026
Primary Completion (Estimated)
January 1, 2029
Study Completion (Estimated)
December 1, 2029
Last Updated
April 17, 2026
Record last verified: 2026-04
Data Sharing
- IPD Sharing
- Will share
- Shared Documents
- STUDY PROTOCOL, SAP, CSR
- Time Frame
- Data are available 6 months after the primary publication or approval of the indication studied in the US and EU, whichever is later. Data will be indefinitely available for requesting.
- Access Criteria
- A research proposal should be approved by an independent review panel and researchers should sign a data sharing agreement.
Anonymized individual patient level data will be provided in a secure access environment upon approval of a research proposal and a signed data sharing agreement.