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

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.