OP-1250 (Palazestrant) vs. Standard of Care for the Treatment of ER+/HER2- Advanced Breast Cancer

Key inclusion criteria:

• Adult female or male participants.

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

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

• Previously received a CDK4/6 inhibitor in combination with an endocrine therapy inthe 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.

Key exclusion criteria:

• Symptomatic visceral disease, imminent organ failure, or any other reason that makesthe participant ineligible for endocrine monotherapy.

• Previously received chemotherapy in the advanced/metastatic setting.

• Previously received treatment with elacestrant or an investigational estrogenreceptor-directed therapy.

• History of allergic reactions to study treatment.

• Any contraindications to the selected standard-of-care endocrine therapy in thelocal prescribing information.

• Symptomatic central nervous system metastases, carcinomatous meningitis,leptomeningeal disease, or a spinal cord compression that require immediatetreatment.

• Clinically significant comorbidities such as significant cardiac or cerebrovasculardisease, gastrointestinal disorders that could affect absorption of study treatment.