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)

May 20, 2026 updated by: Eli Lilly and Company

preEMBER: A Phase 2, Open-label Study Evaluating Imlunestrant in Premenopausal Women With Estrogen Receptor-Positive, HER2-Negative Breast Cancer

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.

Study Overview

Status

Not yet recruiting

Conditions

Intervention / Treatment

Study Type

Interventional

Enrollment (Estimated)

600

Phase

  • Phase 2

Contacts and Locations

This section provides the contact details for those conducting the study, and information on where this study is being conducted.

Study Contact

  • Name: Trial questions or participation questions: 1-877-CTLILLY (1-877-285-4559) or
  • Phone Number: 1-317-615-4559
  • Email: LillyTrials@Lilly.com

Study Contact Backup

Study Locations

  • Belgium
      • Brussels, Belgium, 1200
        • Cliniques Universitaires Saint-Luc
        • Principal Investigator:
          • Francois Duhoux
        • Contact:
          • Phone Number: 3227645435
      • Edegem, Belgium, 2650
        • Antwerp University Hospital
        • Principal Investigator:
          • Sevilay Altintas
      • Leuven, Belgium, 3000
        • UZ Leuven
        • Principal Investigator:
          • Patrick Neven
        • Contact:
          • Phone Number: 003216345129
  • France
      • Brest, France, 29609
        • CHRU de Brest
        • Principal Investigator:
          • Laura Deiana
      • Montpellier, France, 34070
        • Centre de Cancerologie du Grand Montpellier
        • Principal Investigator:
          • Cristian Villanueva
        • Contact:
          • Phone Number: 467926155
      • Plérin, France, 22190
        • Hôpital privé des Côtes d'Armor
        • Principal Investigator:
          • Jerome Martin-Babau
      • Saint-Cloud, France, 92210
        • Institut Curie - site Saint-Cloud
        • Principal Investigator:
          • Diana Bello Roufai
  • Germany
      • Bielefeld, Germany, 33604
        • Onkologische Schwerpunktpraxis Bielefeld
        • Principal Investigator:
          • Siemke Steinke
      • Cottbus, Germany, 03048
        • Medizinische Universität Lausitz- Carl Thiem
        • Principal Investigator:
          • Nikola Bangemann
      • Erlangen, Germany, 91054
        • Universitaetsklinikum Erlangen
        • Principal Investigator:
          • Peter Fasching
        • Contact:
          • Phone Number: +4991318533572
      • Essen, Germany, 45136
        • Kliniken Essen-Mitte, Evangelische Huyssens-Stiftung
        • Principal Investigator:
          • Sherko Kümmel
        • Contact:
          • Phone Number: +4920117433005
      • Frankfurt, Germany, 60431
        • Agaplesion Markus Krankenhaus
        • Contact:
          • Phone Number: 00496995332228
        • Principal Investigator:
          • Marc Thill
      • Hildesheim, Germany, 31134
        • Frauenärzte am Bahnhofsplatz
        • Contact:
          • Phone Number: +49 (5121) 59 02 - 0
        • Principal Investigator:
          • Christoph Uleer
      • Mönchengladbach, Germany, 41061
        • Evangelisches Krankenhaus Bethesda Mönchengladbach
        • Principal Investigator:
          • Katja Krauss
      • München, Germany, 80336
        • Klinikum der Ludwig-Maximilians-Universitaet Muenchen
        • Principal Investigator:
          • Nadia Harbeck
        • Contact:
          • Phone Number: 004989440077581
      • München, Germany, 80637
        • Rotkreuzklinikum München gemeinnützige GmbH
        • Principal Investigator:
          • Michael Braun
        • Contact:
          • Phone Number: 00498913033797
      • Trier, Germany, 54290
        • Klinikum Mutterhaus der Borromaerinnen
        • Principal Investigator:
          • Sebastian Jud
      • Troisdorf, Germany, 53840
        • Hämatologisch-Onkologische Schwerpunktpraxis
        • Principal Investigator:
          • Andreas Diel
        • Contact:
          • Phone Number: 022413975660
      • Tübingen, Germany, 72076
        • Universitaetsklinikum Tuebingen
        • Contact:
          • Phone Number: 004970712982211
        • Principal Investigator:
          • Tobias Engler
      • Witten, Germany, 58452
        • Marien Hospital Witten
        • Principal Investigator:
          • Monika Graeser
        • Contact:
          • Phone Number: 004923021733290
      • Wuppertal, Germany, 42283
        • Helios Klinikum Wuppertal
        • Principal Investigator:
          • Vesna Bjelic-Radisic
        • Contact:
          • Phone Number: 0492028961411
  • Ireland
      • Dublin, Ireland, D04 T6F4
        • St. Vincent's University Hospital
        • Contact:
          • Phone Number: 012214000
        • Principal Investigator:
          • Janice Walshe
      • Dublin, Ireland, D08 E9P6
        • St. James's Hospital
        • Principal Investigator:
          • Ciara O Hanlon Brown
        • Contact:
          • Phone Number: 014103000
  • Italy
      • Genova, Italy, 16128
        • Ente Ospedaliero Ospedali Galliera
        • Contact:
          • Phone Number: 0105634501
        • Principal Investigator:
          • Mauro D'Amico
      • Milan, Italy, 20089
        • Humanitas
        • Contact:
          • Phone Number: 0039028224 4089
        • Principal Investigator:
          • carmen criscitiello
      • Milan, Italy, 20141
        • Istituto Europeo di Oncologia IRCCS
        • Principal Investigator:
          • Giuseppe Curigliano
        • Contact:
          • Phone Number: 00390257489215
      • Misterbianco, Italy, 95045
        • Humanitas Istituto Clinico Catanese
        • Principal Investigator:
          • Maria Vita Sanò
      • Prato, Italy, 59100
        • Nuovo Ospedale di Prato-S.Stefano
        • Principal Investigator:
          • Laura Biganzoli
        • Contact:
          • Phone Number: +39 0574 802531
      • Roma, Italy, 00168
        • Fondazione Policlinico Universitario Agostino Gemelli
        • Principal Investigator:
          • Alessandra Fabi
        • Contact:
          • Phone Number: 00390630157337
  • Taiwan
      • Kaohsiung City, Taiwan, 807
        • Kaohsiung Medical University Chung-Ho Memorial Hospital
        • Principal Investigator:
          • Ming-Feng Hou
        • Contact:
          • Phone Number: 8867-3121101 ext.6235
      • Taichung, Taiwan, 407
        • Taichung Veterans General Hospital
        • Principal Investigator:
          • Chih-Chiang Hung
        • Contact:
          • Phone Number: 886-42359-2525-5031
      • Taichung, Taiwan, 404332
        • China Medical University Hospital
        • Principal Investigator:
          • Hwei-Chung Wang
      • Tainan, Taiwan, 704
        • National Cheng Kung University Hospital
        • Principal Investigator:
          • Kuo-Ting Lee
      • Taipei, Taiwan, 10449
        • Mackay Memorial Hospital
        • Principal Investigator:
          • Yuan-Ching Chang
        • Contact:
          • Phone Number: 886975835311
      • Taoyuan, Taiwan, 333
        • Chang Gung Medical Foundation-Linkou Branch
        • Principal Investigator:
          • Shih-Che Shen
  • United States
    • Alabama
      • Birmingham, Alabama, United States, 35205
        • University of Alabama at Birmingham
        • Principal Investigator:
          • Erica Stringer-Reasor
    • Arizona
      • Chandler, Arizona, United States, 85224
        • Ironwood Cancer & Research Centers
        • Principal Investigator:
          • Sumeet Mendonca
    • California
      • Los Angeles, California, United States, 90033
        • USC/Norris Comprehensive Cancer Center
        • Principal Investigator:
          • Daphne Stewart
        • Contact:
          • Phone Number: 323-397-5954
      • Santa Monica, California, United States, 90404
        • UCLA Hematology/Oncology - Parkside
        • Contact:
          • Phone Number: 310-998-4747
        • Principal Investigator:
          • Nicholas McAndrew
    • Colorado
      • Greeley, Colorado, United States, 80631
        • Banner MD Anderson Cancer Center at North Colorado Medical Center
        • Principal Investigator:
          • Esther Mondo
        • Contact:
          • Phone Number: 970-810-3894
      • Loveland, Colorado, United States, 80538
        • Banner MD Anderson Cancer Center at McKee Medical Center
        • Principal Investigator:
          • Esther Mondo
        • Contact:
          • Phone Number: 970-810-3894
    • Florida
      • Altamonte Springs, Florida, United States, 32701
        • AdventHealth Altamonte Springs
        • Principal Investigator:
          • Wassim Mchayleh
    • Georgia
      • Atlanta, Georgia, United States, 30322
        • Winship Cancer Institute
        • Principal Investigator:
          • Manali Bhave
    • Indiana
      • Indianapolis, Indiana, United States, 46202
        • Indiana University Melvin and Bren Simon Cancer Center
        • Principal Investigator:
          • Rina Yadav
    • Massachusetts
      • Boston, Massachusetts, United States, 02215
        • Dana-Farber Cancer Institute
        • Principal Investigator:
          • Erica Mayer
        • Contact:
          • Phone Number: 617-632-2335
      • Boston, Massachusetts, United States, 02114
        • Massachusetts General Hospital
        • Principal Investigator:
          • Seth Wander
        • Contact:
          • Phone Number: 617-726-6500
    • Missouri
      • St Louis, Missouri, United States, 63110
        • Washington University School of Medicine
        • Principal Investigator:
          • Rebecca Aft
    • New York
      • Albany, New York, United States, 12206
        • New York Oncology Hematology, P.C.
        • Principal Investigator:
          • Karen Tedesco
        • Contact:
          • Phone Number: 518-489-0044
      • Shirley, New York, United States, 11967
        • New York Cancer and Blood Specialists
        • Principal Investigator:
          • Richard Zuniga
        • Contact:
          • Phone Number: 631-675-5075
    • North Carolina
      • Chapel Hill, North Carolina, United States, 27514
        • University of North Carolina Medical Center
        • Principal Investigator:
          • Yara Abdou
    • Oregon
      • Portland, Oregon, United States, 97213
        • Providence Portland Medical Center
        • Principal Investigator:
          • Alison Conlin
        • Contact:
          • Phone Number: 503-215-5696
    • Tennessee
      • Nashville, Tennessee, United States, 37203
        • Tennessee Oncology
        • Principal Investigator:
          • Sara Nunnery
    • Texas
      • Houston, Texas, United States, 77030
        • Houston Methodist Hospital
        • Principal Investigator:
          • Hanh Mai
      • Houston, Texas, United States, 77030-4009
        • University of Texas MD Anderson Cancer Center
        • Principal Investigator:
          • Taiwo Adesoye
        • Contact:
          • Phone Number: 832-728-7423
      • Houston, Texas, United States, 77030
        • Oncology Consultants P.A.
        • Principal Investigator:
          • Ricardo Alvarez
        • Contact:
          • Phone Number: 713-600-0900
      • Round Rock, Texas, United States, 78665
        • Baylor Scott & White Medical Center - Round Rock
        • Principal Investigator:
          • Christal Murray
        • Contact:
          • Phone Number: 512-509-0200
    • Utah
      • Salt Lake City, Utah, United States, 84112
        • Huntsman Cancer Institute
        • Principal Investigator:
          • Jairam Krishnamurthy
        • Contact:
          • Phone Number: 801-585-0236
    • Vermont
      • Burlington, Vermont, United States, 05405
        • The University of Vermont Medical Center Inc.
        • Principal Investigator:
          • Peter Kaufman
    • Virginia
      • Charlottesville, Virginia, United States, 22903
        • University Of Virginia Health System
        • Principal Investigator:
          • Patrick Dillon
        • Contact:
          • Phone Number: 434-924-8073
      • Fairfax, Virginia, United States, 22031
        • Inova Schar Cancer Institute
        • Principal Investigator:
          • Jennifer Matro

Participation Criteria

Researchers look for people who fit a certain description, called eligibility criteria. Some examples of these criteria are a person's general health condition or prior treatments.

Eligibility Criteria

Ages Eligible for Study

  • Adult
  • Older Adult

Accepts Healthy Volunteers

No

Description

Inclusion Criteria:

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
  • 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.

Exclusion Criteria:

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.
  • 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 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.
  • Completed or discontinued prior adjuvant ET >6 months prior to screening.
  • Have received prior therapy with any selective estrogen receptor degrader (SERD).
  • Receiving current exogenous reproductive hormone therapy.

Study Plan

This section provides details of the study plan, including how the study is designed and what the study is measuring.

How is the study designed?

Design Details

  • Primary Purpose: Treatment
  • Allocation: Randomized
  • Interventional Model: Parallel Assignment
  • Masking: None (Open Label)

Arms and Interventions

Participant Group / Arm
Intervention / Treatment
Experimental: Cohort 1 Arm A
Imlunestrant will be given orally
Drug: Imlunestrant
Given orally
Other Names:
  • LY3484356
Experimental: Cohort 1 Arm B - Imlunestrant + Goserelin
Imlunestrant will be given orally and goserelin will be given subcutaneously (SC)
Drug: Goserelin
Given SC
Drug: Imlunestrant
Given orally
Other Names:
  • LY3484356
Active Comparator: Cohort 1 Arm C - Tamoxifen
Tamoxifen will be given orally
Drug: Tamoxifen 20 mg
Given orally
Experimental: Cohort 2 Arm A - Imlunestrant
Imlunestrant will be given orally
Drug: Imlunestrant
Given orally
Other Names:
  • LY3484356
Active Comparator: Cohort 2 Arm B - Tamoxifen
Tamoxifen will be given orally
Drug: Tamoxifen 20 mg
Given orally

What is the study measuring?

Primary Outcome Measures

Outcome Measure
Time Frame
Change from Baseline in Antigen Kiel (Ki-67) Expression
Time Frame: Baseline, Day 29
Baseline, Day 29
Rate of Symptomatic Ovarian Cysts
Time Frame: Up to Day 180
Up to Day 180

Secondary Outcome Measures

Outcome Measure
Time Frame
Change from Baseline in Estrogen Receptor (ER) Expression
Time Frame: Baseline, Day 29
Baseline, Day 29
Change from Baseline in Progesterone Receptor (PR) Expression
Time Frame: Baseline, Day 29
Baseline, Day 29
Rate of Complex Ovarian Cysts
Time Frame: Up to Day 180
Up to Day 180

Collaborators and Investigators

This is where you will find people and organizations involved with this study.

Sponsor

Eli Lilly and Company

Investigators

  • 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

Publications and helpful links

The person responsible for entering information about the study voluntarily provides these publications. These may be about anything related to the study.

Helpful Links

Study record dates

These dates track the progress of study record and summary results submissions to ClinicalTrials.gov. Study records and reported results are reviewed by the National Library of Medicine (NLM) to make sure they meet specific quality control standards before being posted on the public website.

Study Major Dates

Study Start (Estimated)

May 1, 2026

Primary Completion (Estimated)

January 1, 2029

Study Completion (Estimated)

December 1, 2029

Study Registration Dates

First Submitted

December 11, 2025

First Submitted That Met QC Criteria

December 15, 2025

First Posted (Actual)

December 17, 2025

Study Record Updates

Last Update Posted (Actual)

May 22, 2026

Last Update Submitted That Met QC Criteria

May 20, 2026

Last Verified

May 1, 2026

More Information

Terms related to this study

Additional Relevant MeSH Terms

Other Study ID Numbers

  • 27511
  • 2025-523258-15-00 (Ctis)
  • J2J-MC-JZLL (Other Identifier: Eli Lilly and Company)

Plan for Individual participant data (IPD)

Plan to Share Individual Participant Data (IPD)?

YES

IPD Plan Description

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.

IPD Sharing 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.

IPD Sharing Access Criteria

A research proposal should be approved by an independent review panel and researchers should sign a data sharing agreement.

IPD Sharing Supporting Information Type

  • STUDY_PROTOCOL
  • SAP
  • CSR

Drug and device information, study documents

Studies a U.S. FDA-regulated drug product

Yes

Studies a U.S. FDA-regulated device product

No

This information was retrieved directly from the website clinicaltrials.gov without any changes. If you have any requests to change, remove or update your study details, please contact register@clinicaltrials.gov. As soon as a change is implemented on clinicaltrials.gov, this will be updated automatically on our website as well.

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