Study of Abemaciclib and Elacestrant for Patients with Brain Metastasis from ER+/HER-2- Breast Cancer

Inclusion Criteria

• Signed informed consent before any study activities.
• Women or men aged 18 years or older.
• Women can be postmenopausal or pre/perimenopausal.
• Must have ER-positive, HER-2 negative breast cancer confirmed by lab tests.
• In Phase 2, must have at least one active and measurable brain metastasis.
• Stable or decreasing corticosteroid dose for at least 7 days before starting the study.
• Stable neurological symptoms for at least 2 weeks before starting the study.
• Previous treatment in the metastatic setting must include at least one endocrine therapy and up to two chemotherapy regimens.
• Documented progression or recurrence of cancer.
• ECOG performance status of 0 to 2.
• Adequate bone marrow and organ function based on specific lab tests.
• Willingness to follow study visit schedule and requirements.

Exclusion Criteria

• Immediate need for CNS-specific treatment.
• Imminent organ failure or visceral crisis.
• Leptomeningeal metastases.
• No prior treatment for advanced/metastatic breast cancer.
• Previous use of Abemaciclib in the metastatic setting.
• Previous use of Elacestrant or similar investigational drugs.
• Another cancer within 3 years, except for certain skin or cervical cancers.
• Participation in another breast cancer study.
• Recent anti-cancer treatment within specified timeframes.
• Uncontrolled infections or significant medical conditions.
• Major surgery within 4 weeks of starting the study.
• Inability to take oral medication or gastrointestinal issues.
• Women of childbearing potential not using effective contraception.
• Men not using effective contraception with partners of childbearing potential.
• Pregnant or breastfeeding women.
• Known intolerance to study drugs.
• Recent use of certain medications or herbal supplements.
• Recent vaccination, including COVID-19, within 7 days before starting the study.
• Severe medical or psychiatric conditions that may affect participation.