Inclusion Criteria:

- Have a diagnosis of ER+, HER2- early-stage, resected, invasive breast cancer without
evidence of distant metastasis.

- Participants must have received at least 24 months but not more than 60 months of any
adjuvant ET, from time of adjuvant ET initiation.

- Participants may have received (neo) adjuvant chemotherapy and/or targeted therapy
with a CDK4/6- or PARP- inhibitor.

- Must have an increased risk of disease recurrence based on clinical-pathological risk
features.

- Have a Performance Status of 0 or 1 on the Eastern Cooperative Oncology Group scale.

- Have adequate organ function.

Exclusion Criteria:

- Have any evidence of metastatic disease (including contralateral ALN) or inflammatory
breast cancer at primary breast cancer diagnosis.

- Participants with more than a 6-month consecutive gap in therapy during the course of
prior adjuvant ET.

- Participants who have completed or discontinued prior adjuvant ET >6 months prior to
screening.

- Participants with a history of previous breast cancer are excluded, with the exception
of ipsilateral DCIS treated by locoregional therapy alone ≥5 years ago.

- Pregnant, breastfeeding, or expecting to conceive or father children within the
projected duration of the trial, starting with the screening visit through 180 days
after the last dose of study intervention.

- Participant has previously received ET of any duration for breast cancer prevention
(tamoxifen or AIs) or raloxifene.

- Participants with a history of any other cancer.

- Have serious preexisting medical conditions that, in the judgment of the investigator,
would preclude participation in this study.

Note: Other protocol defined Inclusion/Exclusion Criteria may apply.

Eligibility last updated 3/20/2024. Questions regarding updates should be directed to the study team contact.