A Study of Imlunestrant (LY3484356) in Premenopausal Women With Estrogen Receptor-Positive (ER+) Human Epidermal Growth Factor Receptor 2 Negative (HER2-) Early Breast Cancer

Conditions

• Breast Neoplasms

Eligibility Criteria

Sex

FEMALE

Age

18 Years - N/A

Healthy Volunteers

Not accepted

Interventions

• Imlunestrant — DRUG
  Given orally
• Goserelin — DRUG
  Given SC
• Tamoxifen 20 mg — DRUG
  Given orally

Study Details

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.

Key Dates

First listed

Dec 17, 2025

Start date

May 13, 2026

Status verified

Jul 2026

Primary completion

Jan 31, 2029

Completion

Dec 31, 2029

Study Design

Enrollment

600 participants (estimated)

Allocation

RANDOMIZED

Intervention model

PARALLEL

Primary purpose

TREATMENT

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

Primary Outcome Measure

Change from Baseline in Antigen Kiel (Ki-67) Expression [ Time Frame: Baseline, Day 29 ]

Central Contacts

• Trial questions or participation questions: 1-877-CTLILLY (1-877-285-4559) or
  1-317-615-4559
  [email protected]
• Physicians interested in becoming principal investigators please contact
  [email protected]

Locations (29)

Find similar trials in Birmingham, AL

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