• Adult female or male participants.

• ER+, HER2- locally advanced or metastatic breast cancer that is not amenable to curative therapy.

• Evaluable disease (measurable disease or bone-only disease).

• Previously received a CDK4/6 inhibitor in combination with an endocrine therapy in the advanced setting. One additional line of ET as a monotherapy is allowed. Duration of the most recent prior ET must be at least 6 months.

• Eastern Cooperative Oncology Group (ECOG) performance status of 0 or 1.

• Adequate hematologic, hepatic, and renal functions.

• Female participants can be pre-, peri- or postmenopausal.

• Male and pre- or peri-menopausal female participants must be willing to take a GnRH (or LHRH) agonist.