A Study of LY3484356 in Women With Breast Cancer Before Having Surgery

EMBER-2: A Phase 1, Open-Label, Preoperative Window Study Evaluating the Biological Effects of LY3484356 in Post-menopausal Women With Stage I-III Estrogen Receptor-Positive, HER2-Negative Breast Cancer

The purpose for this study is to see if the study drug, LY3484356, is safe and to determine what effects it has on breast cancer in participants with Estrogen Receptor Positive (ER+), HER2 Negative (HER2-) early stage (stage I-III) breast cancer, when given prior to surgery. Participation in this study could last up to 2.5 months.

Inclusion Criteria:

• Have histologically confirmed invasive ER+, HER2- breast carcinoma
• Be willing and able to provide pre- and on-treatment tumor samples
• Have a performance status of 0 or 1 on the Eastern Cooperative Oncology Group scale
• Have adequate organ function
• Be able to swallow capsules
• Be a postmenopausal woman

Exclusion Criteria:

• Have bilateral invasive breast cancer
• Have metastatic breast cancer
• Plan to receive concurrent neoadjuvant therapy with any other non-protocol anti-cancer therapy
• Have had prior therapy (of any kind) for an invasive or non-invasive breast cancer
• Have had prior radiotherapy to the ipsilateral chest wall for any malignancy
• Have had prior anti-estrogen therapy with raloxifene, tamoxifen, aromatase inhibitor, or other selective estrogen receptor modulator (SERM), either for osteoporosis or prevention of breast cancer
• Have had prior hormone-replacement therapy within 4 weeks of the start of study treatment
• Have had major surgery within 28 days prior to randomization to allow for post-operative healing of the surgical wound and site(s)
• Have certain infections such as hepatitis or tuberculosis or HIV that are not well controlled
• Have another serious medical condition
• Have a history of any other cancer (except nonmelanoma skin cancer or carcinoma in-situ of the cervix), unless in complete remission with no therapy for a minimum of 3 years