Recruiting
Phase 2

Imlunestrant & Tamoxifen

Sponsor:

Eli Lilly and Company

Code:

NCT07287098

Conditions

Breast Neoplasms

Eligibility Criteria

Sex: Female

Age: 18+

Healthy Volunteers: Not accepted

Interventions

Imlunestrant

Goserelin

Tamoxifen 20 mg

Study Details

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.

Conditions

Breast Neoplasms

Study ID

NCT07287098

Start date

May 13, 2026

Status verified date

Sep, 2026

Completion date

Dec, 2029

Anticipated

Primary completion date

Jan, 2029

Anticipated

Eligibility Criteria

Eligibility Criteria

Sex: Female

Age: 18+

Healthy Volunteers: Not accepted

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 Design

Enrollment

600 participants

Anticipated

Allocation

Randomized

Intervention Model

Parallel Assignment

Primary purpose

Treatment

Interventions and Outcome Measures

Arms

experimental: Cohort 1 Arm A

Imlunestrant will be given orally

experimental: Cohort 1 Arm B - Imlunestrant + Goserelin

Imlunestrant will be given orally and goserelin will be given subcutaneously (SC)

active comparator: Cohort 1 Arm C - Tamoxifen

Tamoxifen will be given orally

experimental: Cohort 2 Arm A - Imlunestrant

Imlunestrant will be given orally

active comparator: Cohort 2 Arm B - Tamoxifen

Tamoxifen will be given orally

Interventions

Imlunestrant

Given orally

Goserelin

Given SC

Tamoxifen 20 mg

Given orally

Primary outcome measure

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

Central Contacts and Locations

Central contacts

Trial questions or participation questions: 1-877-CTLILLY (1-877-285-4559) or

1-317-615-4559LillyTrials@Lilly.com

Physicians interested in becoming principal investigators please contact

clinical_inquiry_hub@lilly.com

Locations

Indiana University Melvin and Bren Simon Cancer Center

Recruiting

Indianapolis, Indiana, United States, 46202

Principal Investigator:

Rina Yadav

New York Cancer and Blood Specialists

Recruiting

Shirley, New York, United States, 11967

Contacts

631-675-5075

Principal Investigator:

Richard Zuniga

Tennessee Oncology

Recruiting

Nashville, Tennessee, United States, 37203

Principal Investigator:

Sara Nunnery

University of Texas MD Anderson Cancer Center

Recruiting

Houston, Texas, United States, 77030-4009

Contacts

832-728-7423

Principal Investigator:

Taiwo Adesoye

Oncology Consultants P.A.

Recruiting

Houston, Texas, United States, 77030

Contacts

713-600-0900

Principal Investigator:

Ricardo Alvarez

More Information

Sponsor

Eli Lilly and Company

Last update posted

Sep 4, 2026

Last verified

Sep, 2026

Trial information was received from ClinicalTrials.gov and was last updated on 2026-09-09. This information was provided to ClinicalTrials.gov by Eli Lilly and Company on 2026-09-04.